water

Article

Spatial Distribution of Benthic MacroinvertebrateAssemblages in Relation to Environmental Variablesin Korean Nationwide StreamsYung-Chul Jun 1 Nan-Young Kim 1 Sang-Hun Kim 2 Young-Seuk Park 3 Dong-Soo Kong 4 andSoon-Jin Hwang 15

Received 23 October 2015 Accepted 15 January 2016 Published 20 January 2016Academic Editor Kevin Strychar

1 Department of Environmental Science Konkuk University Seoul 143-701 Koreaeco072empalcom (Y-CJ) celeste0konkukackr (N-YK)

2 The National Institute of Environmental Research Incheon 404-170 Korea haemykoreakr3 Department of Life and Nanopharmaceutical Sciences and Department of Biology Kyung Hee University

Seoul 130-701 Korea parkyskhuackr4 Department of Biology Kyonggi University Suwon 443-760 Korea dskongkyonggiackr5 Department of Environmental Health Science Konkuk University Seoul 143-701 Korea Correspondence sjhwangkonkukackr Tel +82-2-450-3748 Fax +82-2-456-5062

Abstract Conserving and enhancing freshwater biodiversity are global issues to ensure ecosystemintegrity and sustainability To meet this it is critical to understand how the biological assemblages aredetermined by environmental gradients in different spatial scales Nevertheless information on theirlarge-scale environmental relationships remains scarce in Korea We aimed to understand nationwidespatial distribution patterns of benthic macroinvertebrates and important environmental factorsaffecting their distribution in 388 streams and rivers across Korea A total of 340 taxa belonging to113 families in 23 orders of five phyla were identified Assemblage composition in most Koreanstreams included a few predominant colonizers and a majority of rare taxa Cluster analysis based onbenthic macroinvertebrates classified a total of 720 sampling sites into five clusters according to thepollution levels from fast-flowing less polluted streams with low electrical conductivity to moderatelyor severely polluted streams with high electrical conductivity and slow water velocity Canonicalcorrespondence analysis revealed that altitude water velocity and streambed composition were themost important determinants rather than watershed and water chemistry variables for explainingthe variation in macroinvertebrate assemblage patterns The results provide basic information forestablishing the conservation and restoration strategies of macroinvertebrate biodiversity againstanthropogenic disturbances and developing more confident bio-assessment tools for diagnosingstream ecosystem integrity

Keywords macroinvertebrate biodiversity spatial distribution environmental relationecosystem integrity

1 Introduction

Freshwater ecosystems occupying a very tiny fraction of the Earthrsquos surface support remarkablebiodiversity and abundance of benthic macroinvertebrates [12] However growing humanpressures have substantially deteriorated the overall ecological integrity and induced a biodiversitycrisis This problem now increasingly becomes a global issue and thereby calls attention toestablish relevant conservation strategies and wise management practices to maintain sustainablefreshwater environments

Water 2016 8 27 doi103390w8010027 wwwmdpicomjournalwater

Water 2016 8 27 2 of 20

Although Asian riverine ecosystems contain remarkable taxonomic diversity as well as high levelsof endangerment and endemism studies on biodiversity and ecology of these ecosystems have beenpoor [13] Year-to-year variations in seasonality and its relationship to monsoonal climate particularlyin temperate Asian regions can be major drivers that profoundly affect the hydrologic regime andgeomorphology in stream environments consequently determining the distribution and abundance ofmacroinvertebrates [4] For example a wet season low and a dry season high are expected for periodicseasonal patterns in abundance depending on the frequency and intensity of summer monsoon rainfallHowever habitat destruction and water quality degradation in Asian river systems have becomemore dramatically epidemic than any other continents due to the fast growing human population anddemands for economic development [56] Because failure of conservation efforts has mainly resultedfrom scant evidence on river ecology the priority over scientific and practical challenges to overcomethis circumstance must be put on establishing species inventories and ecological information based onthe accumulation of region-specific case studies particularly at watershed or national scales [47]

Macroinvertebrate diversity and abundance are significant community attributes that arecontrolled by a variety of mechanisms at different spatial scales A number of studies have documentedhow macroinvertebrate assemblages respond to environmental variables and which variablesbest explain their distribution and abundance Some studies showed good relationships amongmacroinvertebrate assemblages chemical variables [8] and the organic energy base [9] whereashabitat-related physical factors were widely demonstrated as primary contributors such as substratecomposition [10] flow and current velocity [11] elevation and stream size [12] and temperature [13]Vegetation geology and human land use are also important for their spatial distribution [1415]While there remains a large number of documents focusing on such environmental relationships atfiner spatial scales studies on large-scale spatial patterns have been relatively small (eg at nationalscale [1617] and at continental scale [1819])

Studies on the spatial distribution patterns of macroinvertebrate assemblages based on theirenvironmental relationships are crucial Firstly those studies provide fundamental information for theconservation and restoration of biodiversity against anthropogenic disturbances Secondly knowledgeof the species response to environmental gradients is important to separate the effects of pollution fromthe effects of natural variables on community structures [20] Thirdly it is possible to develop moreconfident bio-assessment tools for diagnosing stream ecosystem integrity because macroinvertebrateresponds sensitively to environmental alterations that lead to changes in composition and communitystructures [2122] Thus we performed a synoptic study of the large scale spatial distribution of benthicmacroinvertebrates in relation to environmental variables Specifically the objectives of this studywere (i) to characterize the spatial distribution and assemblage structures of macroinvertebrates(ii) to identify environmental distinction of Korean stream ecosystems based on their assemblages(iii) to determine major environmental variables that affect their distribution and (iv) to providemethodological considerations to improve biomonitoring programs particularly focusing on samplingprocedures A relevant scientific basis would then be established with these data for developingsustainable management conservation practices and a reliable biomonitoring program The resultsof this study could also contribute to a better understanding of the spatial distribution of freshwatermacroinvertebrates in poorly explored Asian regions

2 Materials and Methods

21 Study Area

Samples were collected at 720 sampling sites from 388 streams and rivers on a nationwide scale inSouth Korea South Korea is located between 37˝001 N latitude and 127˝301 E longitude encompassingthe southern half of the Korean Peninsula with an entire area of approximately 100033 km2 The annualprecipitation is 1308 mm but there is substantial variation among seasons [23] severe flooding eventsduring the summer monsoon period and base flow or even drought conditions in the other seasons

Water 2016 8 27 3 of 20

The entire stream system throughout South Korea comprises five watersheds including fivelarge rivers their tributaries and other small independent streams (Figure 1) Land use types in eachwatershed generally display well-managed forests upstream and agricultural and urban developmentfrom middle to lower regions Most Korean streams have suffered from a variety of human activitiesthat alter the physicochemical stream environments particularly caused by channel modification andeutrophication [24]

Among 720 sampling sites the largest number of sites belonged to the Han River watershed (HRW)(n = 320) followed by the Nakdong River watershed (NRW) (n = 130) the Geum River watershed(GRW) (n = 130) the Youngsan River watershed (YRW) (n = 76) and the Seomjin River watershed(SRW) (n = 64) It was assumed that such a nationwide survey covered the majority of stream types inKorea to understand how lotic macroinvertebrates are spatially distributed in relation to environmentalfactors Field sampling was conducted during spring (May 2009) under base flow conditions becausethe highest benthic macroinvertebrate diversity was expected at that time More information of thefive major river watersheds in Korea can be found in Hwang et al [25]

Figure 1 Geographic locations of the study sites Five macroinvertebrate-based site groups wereclassified as G1a (n = 126 black circles) G1b (n = 199 white circles) G2a (n = 106 white triangles) G2b(n = 118 gray triangles) and G2c (n = 171 black triangles) based on Soslashrenson distance measure clusteranalysis Dark lines indicate the five large rivers and the light lines display their tributaries and smallindependent streams

22 Measurement of Environmental Variables

Environmental variables were measured both in the field and in the laboratory to define theireffects on benthic macroinvertebrate assemblages Three categories of environmental variables were

Water 2016 8 27 4 of 20

considered such as watershed-related regional variables physical in-stream properties and waterquality elements

Altitude and land-use types were considered as regional variables for watershed characteristicsThe altitude at each sampling site was obtained using digital elevation data (Openmate Inc SeoulKorea) The proportion of prevalent land use types was determined for each sampling site using atopographic map (150000)

Physical in-stream properties were measured during field surveys (i) stream width for thedistance from bank to bank at a transect representative of the stream channel (ii) wetted stream widthusing a range finder (model LRM-1500M Newcon Optik Inc Toronto ON Canada) (iii) water depthof the vertical distance from the water surface to stream bottom (iv) current velocity at riffles or glidingruns using a current meter (3000-LX Swoffer Instruments Inc Tukwila WA USA) or calculated bythe Craig method [2627] (v) percent substrate composition visually estimated as fine (lt2 mm) andcoarse-sized particles (ě2 mm)

Water quality variables such as pH water temperature dissolved oxygen (DO) turbidity andelectrical conductivity (EC) were measured with a multi-probe portable meter (eg YSI 6920 YSI IncYellow Springs OH USA or Horiba U-22XD Kyoto Japan) at the center of each sampling stretch Twoliters of water samples were collected in sterilized plastic bottles at each site kept in a container withice and transported to the laboratory Laboratory measurements were conducted to determine thebiochemical oxygen demand (BOD) total nitrogen (TN) and total phosphorus (TP) following Standardmethods [28]

23 Sampling of Benthic Macroinvertebrate

A Surber sampler (30 cm ˆ 30 cm 1 mm mesh) was employed to collect benthicmacroinvertebrates Samplings were conducted at fast-flowing riffle or gliding run habitats (inthe case when suitable riffles were not available) within 100 m Quantitative samples were taken fromthree randomly selected riffles at each site pooled together in a 500 mL plastic bottle with 80 ethanoland labeled The sampling device and procedures followed the guidelines of the National AquaticEcological Monitoring Program (NAEMP) Korea [27]

After field sampling all organisms were hand-sorted from detritus and inorganic materialand stored in 70 ethanol Subsampling was permitted only for dominant taxonomic groups (egOligochaeta Ephemerellidae Chironomidae and Hydropsychidae) with large numbers of specimensavailable in each sample Each macroinvertebrate specimen was identified to the lowest possibletaxonomic level (usually genus or species) However several taxa with limited systematic information(eg Coleoptera and Diptera) were identified only to the family level All individuals were countedand converted to individualsm2

24 Data Analysis

Differences in environmental variables and macroinvertebrate assemblages were identified amongthe five major river watersheds by the KruskalndashWallis test followed by Dunnrsquos nonparametric multiplecomparison test if they are significantly different (p lt 005) Spearmanrsquos rank correlation analysiswas used to indicate the relationships between the most dominant taxa and environmental variablesA cluster analysis was conducted to classify the benthic macroinvertebrate communities using theflexible beta method (beta = acute025) with the Soslashrenson distance measure [29] Samples were classifiedinto clusters based on similarities in the community composition The multi-response permutationprocedure (MRPP [30]) which is a non-parametric method to test for differences in assemblagestructure among a priori defined groups [31] was conducted to evaluate differences among clustersDifferences in environmental variables among clusters were evaluated using the KruskalndashWallistest and Dunnrsquos nonparametric multiple comparison test The KruskalndashWallis test Dunnrsquos test andSpearman correlation analysis were performed with STATISTICA software (StatSoft Inc version 7Tulsa OK USA)

Water 2016 8 27 5 of 20

Indicator species analysis (IndVal [32]) was performed to evaluate potential indicator speciesin each cluster defined in advance The indicator value of a species is the product of its relativeabundance and frequency (ˆ 100) ranging from 0 (no indication) to 100 (perfect indication) [33]A perfect indicator of a particular group should be faithful and exclusive to that group never occurringin other groups [29] A species in a cluster that had an indicator value greater than in any othercluster was defined as good indicator species for that cluster in this study A Monte Carlo method wasperformed to test the significance of indicator values

Canonical correspondence analysis (CCA) was used to relate macroinvertebrate assemblages toenvironmental variables and to identify which environmental variables could best differentiate amongthe clusters [34] Monte-Carlo simulations were carried out to verify whether variables exerted asignificant effect (p lt 005) on macroinvertebrate distributions For the cluster analysis and CCA thosetaxa with less than 02 of total abundance were excluded to minimize the effects of rare taxa Taxaabundance data were transformed to log (x + 1) in both analyses to down-weight the effects of dominanttaxa Square-root-transformation was used for the environmental parameters expressed in percentages(eg type of land use and substrate composition) and the other variables were transformed to log(x + 1) except pH After these processes all environmental variables were rescaled in the range of0 and 1 based on the minimum-maximum range normalization [25] Spearman correlation coefficientsbetween scores and environmental variables were calculated to assist interpretation of changes incommunity profile using STATISTICA software (StatSoft Inc version 7 Tulsa OK USA) Clusteranalysis IndVal MRPP and CCA were conducted using PC-ORD software (ver 425 MjM SoftwareDesign Gleneden Beach OR USA) [34]

3 Results

31 Environmental Characteristics

Despite a large variation physicochemical factors were significantly different among watersheds(Table 1) On average the altitude percent forest and water velocity of the HRW and SRW werethe higher than the other watersheds The SRW streambeds were very heterogeneous with thehighest percentage of coarse-sized particles whereas those of the YRW contained a large amountof fine sediment High altitude fast water velocity and substrate complexity in both the HRW andSRW indicated good in-stream habitat conditions and potential to support high biodiversity andabundance of macroinvertebrates (Table 1a) The other three watersheds (NRW GRW and YRW) werecharacterized by low altitude and a high proportion of agricultural land use

Water quality parameters varied more prominently than physical variables among riverwatersheds (Table 1b) The average concentrations of DO BOD TN TP and turbidity were generallylower in the SRW than those in the other watersheds EC varied widely depending on the samplinglocation with the highest values near estuaries Nutrient-related factors were particularly high in theGRW YRW and HRW

32 Benthic Macroinvertebrate Assemblages

A total of 340 taxa belonging to 113 families in 23 orders of five phyla were identified in the fivemajor river watersheds during the survey Most of these were aquatic insects (272 species) including144 Ephemeroptera Plecoptera Trichoptera (EPT 62 mayflies 24 stoneflies and 58 caddisflies) taxaand 35 Dipteran species Taxa richness from the 720 sampling sites ranged from 0 to 49 with amean of 144 (˘ 91) with the highest diversity at HRW and the lowest in YRW (Table 2a) In contrasthomogeneous streambeds and nutrient enrichment attributed to relatively low Shannon diversity indexand high dominance index in both the NRW and YRW The proportion of EPT taxa richness rangedfrom 401 (GRW) to 548 (SRW) One-way ANOVA revealed that taxa abundance significantlydiffered among river watersheds at p lt 001 whereas there were no great differences for the relativeabundance of each taxonomic group among watersheds (Table 2b)

Water 2016 8 27 6 of 20

Table 1 Descriptive statistics of (a) regional and physical instream variables and (b) chemical variables in the five major river watersheds the Han River (HRW)Nakdong River (NRW) Geum River (GRW) Youngsan River (YRW) and Seomjin River Watershed (SRW) Top and bottom lines of each variable indicate theaverage with standard deviation (in parenthesis) and the range respectively KruskalndashWallis test (KndashW) was performed with the environmental variables to comparethe differences of each variable among river watersheds The same small letters indicate no significant difference based on Dunnrsquos multiple comparison testsAbbreviations DO dissolved oxygen BOD biochemical oxygen demand EC electrical conductivity TN total nitrogen TP total phosphorus

Variable HRW (n = 320) NRW (n = 130) GRW (n = 130) YRW (n = 76) SRW (n = 64) Total (n = 720) p (KndashW)

(a) Regional and physical instream variables

Altitude (m) 1475 (1516) d 896 (1191) bc 577 (612) ab 325 (351) a 1181 (793) cd 1061 (1262)000010ndash7210 10ndash6290 00ndash2780 00ndash2110 10ndash3350 00ndash7210

Urban317 (320) b 230 (308) ab 309 (358) b 314 (302) b 146 (124) a 284 (315)

00000ndash100 0ndash100 0ndash100 0ndash90 0ndash80 0ndash100

Agriculture 247 (275) a 425 (310) bc 466 (389) c 454 (307) c 359 (207) b 350 (317)00000ndash100 0ndash100 0ndash100 0ndash90 0ndash80 0ndash100

Forest358 (332) b 314 (278) b 179 (301) a 226 (243) a 488 (246) c 315 (313)

00000ndash100 0ndash100 0ndash100 0ndash100 0ndash95 0ndash100

Water velocity (cms) 538 (279) c 147 (140) a 381 (345) b 177 (131) a 419 (260) b 390 (304)000000ndash1400 00ndash670 00ndash1377 04ndash475 14ndash982 00ndash1400

Fine particles 311 (279) b 365 (368) bc 436 (345) c 547 (313) d 108 (229) a 350 (326)000000ndash1000 00ndash1000 00ndash1000 00ndash1000 00ndash1000 00ndash1000

Coarse particles 686 (281) c 635 (368) bc 564 (345) b 453 (313) a 892 (229) d 648 (327)000000ndash1000 00ndash1000 00ndash1000 00ndash1000 00ndash1000 00ndash1000

(b) Chemical variables

pH 81 (08) bc 80 (08) ab 83 (09) c 80 (07) ab 78 (07) a 81 (08)000365ndash101 62ndash106 70ndash111 67ndash101 67ndash96 62ndash111

DO (mgL) 978 (247) a 1081 (236) b 1086 (336) b 1006 (169) a 957 (132) a 1017 (254)0000242ndash1610 255ndash1734 274ndash1786 619ndash1540 711ndash1269 242ndash1786

BOD (mgL) 31 (37) bc 19 (13) a 37 (20) c 35 (30) bc 27 (17) b 30 (29)000003ndash375 04ndash104 08ndash91 03ndash133 03ndash123 03ndash375

EC (microScm)2998 (3376) a 13587 (60671) b 4048 (3498) a 2707 (4026) a 12846 (58234) b 5944 (31416)

0000103ndash27290 197ndash440000 861ndash27800 285ndash30820 326ndash333600 103ndash440000

TN (mgL) 315 (297) b 210 (166) a 360 (242) b 336 (359) b 232 (139) a 299 (269)0000038ndash2378 032ndash1130 029ndash1427 069ndash2771 044ndash577 029ndash2771

TP (mgL) 015 (041) bc 007 (015) ab 014 (015) bc 021 (028) c 005 (006) a 013 (030)0000000ndash559 000ndash091 001ndash101 001ndash166 000ndash032 000ndash559

Turbidity (NTU) 93 (166) b 86 (74) b 139 (223) b 78 (459) b 21 (33) a 92 (212)000000ndash1520 00ndash342 04ndash1824 00ndash4000 00ndash169 00ndash4000

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Table 2 Assemblage attributes (a) and average abundance (individualsuml macute2) (b) of benthic macroinvertebrates with standard deviation (in parenthesis) in fivemajor river watersheds the Han River (HRW) Nakdong River (NRW) Geum River (GRW) Youngsan River (YRW) and Seomjin River Watershed (SRW) Relativeabundance (RA) indicated as an average of total density for each taxonomic group KruskalndashWallis test (KndashW) was performed for each taxonomic group The samesmall letters indicate no significant difference based on Dunnrsquos multiple comparison test

Biological Attributes HRW (n = 320) NRW (n = 130) GRW (n = 130) YRW (n = 76) SRW (n = 64) Total (n = 720) RA p (KndashW)

(a) Assemblage attributes

Taxa richness 157 (94) a 117 (73) b 155 (108) a 106 (63) b 151 (80) a 144 (91) - 0000EPT richness 103 (80) c 53 (55) a 76 (82) b 45 (47) a 85 (54) b 81 (75) - 0000

Taxa abundance 28675 (97919) b 8649 (10352) a 39444 (59647) b 9470 (10541) a 6120 (5482) a 22971 (71210) - 0000EPT abundance 10669 (17029) b 3032 (7265) a 15525 (24410) c 3164 (5450) a 2786 (3158) a 8674 (16472) - 0000

Dominance index 065 (021) b 070 (020) bc 071 (021) bc 073 (020) c 052 (023) a 067 (022) - 0000Shannon diversity index 233 (100) b 208 (091) b 209 (102) b 179 (094) a 263 (109) c 221 (101) - 0000

(b) Taxa abundance of higher taxonomic group

Non-Insecta

Platyhelminthes 187 (788) 287 (1967) 255 (1024) 99 (492) 172 (378) 207 (1096) 001 0447Nematomorpha 02 (09) 01 (06) 01 (05) 01 (08) 00 (00) 01 (07) 000 0082

Mollusca 107 (394) a 444 (1515) c 304 (543) b 274 (495) b 212 (309) ab 230 (765) 001 0000Annelida 6035 (68262) b 399 (908) a 5483 (29976) b 210 (614) a 681 (917) a 3827 (47310) 020 0000Crustacea 19 (122) a 429 (2143) a 412 (2439) a 1098 (5606) b 14 (70) a 277 (2306) 001 0000

Insecta

Ephemeroptera 6926 (11329) b 3166 (5946) a 5651 (10151) b 1990 (3087) a 3773 (3890) a 5215 (9360) 027 0000Odonata 39 (123) a 42 (124) a 145 (371) b 119 (292) b 07 (22) a 64 (213) 000 0000

Plecoptera 66 (216) b 56 (296) b 42 (215) ab 01 (07) a 07 (42) a 48 (213) 000 0000Hemiptera 11 (93) a 387 (2074) b 250 (1291) ab 255 (2135) ab 00 (03) a 147 (1257) 001 0000

Megaloptera 26 (104) b 12 (60) ab 16 (60) ab 05 (23) a 10 (98) ab 18 (84) 000 0000Coleoptera 153 (976) a 286 (806) a 809 (2008) c 89 (315) a 569 (949) b 326 (1193) 002 0000

Diptera 4493 (7802) b 3098 (4521) b 8062 (18533) c 3441 (7121) b 1050 (1644) a 4469 (10095) 023 0000Trichoptera 5492 (10290) b 3066 (7718) a 8453 (15644) c 1145 (2962) a 1264 (2951) a 4754 (10448) 024 0000Lepidoptera 00 (01) a - 01 (09) b 00 (06) ab - 00 (04) 000 0000Neuroptera - - - 00 (03) - 00 (01) 000 0076

Water 2016 8 27 8 of 20

Korean stream ecosystems were characterized by a few predominant colonizers and a majority ofrare taxa in macroinvertebrate assemblage composition The most abundant and widespread taxa werea worm (Limnodrilus gotoi Hatai) and midge larvae (Chironomidae spp) with their relative abundanceof approximately 50 of total density throughout the whole river watershed Other dominant specieswere mayflies (ie Baetis fuscatus (Linnaeus) Epeorus pellucidus (Brodsky) and Uracanthella punctisetae(Matsumura)) and netspinning caddisflies (Cheumatopsyche brevilineata Iwata Hydropsyche valvataMartynov and Hydropsyche kozhantschikovi Martynov) among the different stream and river systemsmost of which were dominant in somewhat nutrient-rich habitats at middle or lower streams Howeverover 50 (195 taxa) of the fauna was present with low occurring frequency (less than 2 of all sites)and 90 with low abundance (less than 02)

The environmental relationships of the dominant taxa were stronger with the physical variables(ie altitude water velocity and streambed conditions) than with the chemical variables among whichwater velocity was the most significant parameter Consequently significant positive relationshipsexisted in most dominant taxa with peak abundance at a moderate velocity of 50ndash100 cms particularlyfor E pellucidus (r = 0410 p lt 0001) and C brevilineata (r = 0435 p lt 0001) (Figure 2) Baetiella tuberculata(Kazlauskas) U punctisetae and H valvata tended to occur in their highest densities at the fast velocity(120ndash140 cms) No clear tendency was observed for Chironomidae spp

Figure 2 Distribution patterns of dominant macroinvertebrates along with water velocity Data aregiven as arithmetic means with standard deviation Spearmanrsquos rank correlation coefficients betweenwater velocity and abundance of each dominant species are included (a) Uracanthella punctisetae(b) Epeorus pellucidus (c) Baetiella tuberculata (d) Chironomini sp (e) Cheumatopsyche brevilineata(f) Hydropsyche valvata

Water 2016 8 27 9 of 20

33 Macroinvertebrate-Based Site Classification

The cluster analysis based on the similarity in the benthic macroinvertebrate composition largelyclassified the 720 sampling sites into two clusters and subsequently sub-clustered them into five groupsAs a result 126 sampling sites were included in Group 1a 199 sites in Groups 1b 106 sites in Group 2a118 sites in Group 2b and 171 sites in Group 2c (Figure 1) MRPP validated these five groups withsignificant differences (A = 0484 p lt 0001) The differences in environmental variables among theclusters are shown in Figure 3 The most important indicator taxa for each cluster are shown with theirindicator values in Table 3

Figure 3 Distribution of selected environmental variables among the five clusters of the 720 samplingsites which were identified by cluster analysis with Soslashrenson distance measure Box represents the25th and 75th percentiles and whiskers indicate the 5th and 95th percentiles with standard deviations(error bar) The mean (horizontal dotted line) and median (horizontal solid line) are shown in each boxDifferent small letters indicate significant difference based on a Dunnrsquos multiple comparison test atp lt 005

Water 2016 8 27 10 of 20

Table 3 Indicator values () for the most important species (p lt 005) in each cluster group MonteCarlo tests (999 permutations) were used to assess the significance of each species as an indicator forthe respective group (G1andashG2c) In total 50 species whose contribution to total density was higher than02 were analyzed Less important species were not shown in this table

TaxaCluster Group

pG1a G1b G2a G2b G2c

Rhyacophila nigrocephala Iwata 47 16 0 0 0 0001Epeorus nipponicus (Ueacuteno) 46 1 0 0 0 0001Glossosoma KUa 44 4 0 0 0 0001Drunella aculea (Allen) 44 1 0 0 0 0001Hydropsyche orientalis Martynov 40 7 1 1 0 0001

Uracanthella punctisetae(Matsumura)

21 48 6 6 0 0001

Hydropsyche valvata Martynov 6 46 2 9 0 0001Cheumatopsyche brevilineataIwata

15 41 5 10 0 0001

Hydropsyche kozhantschikoviMartynov

21 40 3 16 0 0001

Psychomyia sp 0 32 1 5 0 0001

Ephemera orientalis McLachlan 2 20 41 5 2 0001Ecdyonurus levis (Navaacutes) 5 28 40 1 0 0001Ecdyonurus joernensis Bengtsson 0 12 25 1 0 0001Mataeopsephus KUa 0 16 23 0 0 0001Asellus sp 0 2 11 3 6 0001

Hirudo nipponia Whitman 1 10 2 28 4 0001Chironomini sp 1 7 9 27 21 0001Limnodrilus gotoi Hatai 5 12 18 23 9 0001

Micronecta sedula Horvaacuteth 0 0 0 0 20 0001Physa acuta Draparnaud 2 3 2 12 16 0001Micronecta sp 0 0 5 0 5 0007

Total number of significantindicator species

12 21 8 3 3 -

Each cluster was clearly differentiated according to the differences of instream physicochemicalconditions and geographical location of sampling sites The cluster analysis discriminated less pollutedstreams with low EC and fast flowing water (Group 1) from moderately or severely polluted steams withhigh EC and slow water velocity (Group 2) Group 1a (G1a) congregating in the HRW consisted specificallyof mountainous upper streams although a tenth of this group was scattered over the other watershedsexcept the YRW This group consisted of oligotrophic streams with distinguishing features of the highestaltitude the lowest BOD and nutrient concentrations and the fastest water velocity Additionally thecatchment was predominantly comprised of forested area The best indicator species for this group werecharacterized as high sensitivity against organic pollution (eg Rhyacophila nigrocephala Iwata Epeorusnipponicus (Ueacuteno) Drunella aculea (Allen) and Hydropsyche orientalis Martynov) Group 1b (G1b) containedthe largest number of sampling sites and was widely distributed throughout all river watersheds butmostly encompassing the agricultural and forested catchment G1a and G1b closely resembled chemicalenvironments but steam sites belonging to G1b displayed mesotrophic condition with slightly higherBOD and nutrients than those of G1a There existed the largest number of indicator species in G1b amongwhich U punctisetae showed the highest indicator value

G2a mostly included sites located in middle reaches of large rivers and their tributariesparticularly in the NRW and SRW Although Group 2a (G2a) was similar in overall environmentalcharacteristics to G1b G2a was characterized with slightly lower altitude higher EC and a lower watervelocity when compared with G1b Sampling sites suffering from poor water quality with organicdegradation and nutrient enrichment were confined to Group 2b with the highest BOD TN and TPconcentrations These sites were influenced by the highest degree of agriculture andor urbanizationThe significant indicator species of this group were Hirudo nipponia Whitman Chironomini sp and

Water 2016 8 27 11 of 20

L gotoi indicating high trophy and saprobity [35] Water quality conditions in Group 2c (G2c) were aspoor as those of G2b with the highest EC Sites in this group were characterized with the lowest watervelocity and the largest proportion of fine particles because G2c was gathered by streams adjacent toestuaries large rivers and dammed streams The only three weak indicator species appeared in G2c

34 Environmental Variables Affecting Macroinvertebrate Distributions

A CCA was performed to understand how macroinvertebrates were distributed alongenvironmental gradients (Figure 4) Total variability explained in the species data was 159 (Table 4)The eigenvalues of the first CCA axis (0281) and the second CCA axis (0101) were significant (p lt 00199 Monte Carlo permutation test) All three CCA results were significant based on a Monte Carlopermutation test (p lt 001)

Figure 4 Ordination plots constructed by canonical correspondence analysis for all sampling sites(n = 720) The plots present the ordination of sampling sites (a) and macroinvertebrates (b) with relativecontributions of environmental variables (c) for the first two axes Only species contributing gt02to total abundance were included The summary of ordination results is presented in Table 4 and thecodes for each taxon are shown in Appendix Table A1

Water 2016 8 27 12 of 20

Table 4 Spearmanrsquos rank correlation coefficients and probabilities of environmental variables andthe CCA axes ( p lt 001 p lt 005) (a) and summary of CCA results (n = 720) (b) All axes weresignificant based on Monte Carlo permutation procedures

Variables Axis 1 Axis 2 Axis 3

(a) Correlation coefficients

Altitude 0793 0236 0013Stream order acute0105 acute0658 0099

Urban acute0218 0134 acute0317 Agriculture acute0199 acute0273 0133

Forest 0504 0055 0266 Water velocity 0662 acute0054 acute0510

Fine particles acute0744 0325 acute0076 Coarse particles 0747 acute0327 0075

pH 0011 acute0236 0007DO 0304 acute0467 acute0166

BOD acute0550 0164 acute0370 EC acute0196 acute0278 acute0116 TN acute0463 0266 acute0387 TP acute0373 0229 acute0314

(b) Summary of CCA results

Eigenvalue 0281 0101 0073 variance explained in

taxa data 98 35 25

Cumulative varianceexplained 98 133 159

p value 0010 0010 0010

Total variance 2869 - -

The five clusters were well separated in the CCA ordination plot (Figure 4a) Both the G1aand G1b groups with good physicochemical environments were positioned on the right side of theordination plot and G2b and G2c were on the opposite side However the G2a group straddledboth sides Eight environmental variables (ie BOD TN TP altitude water velocity forest fineparticles and coarse particles) had significant correlations with the first axis among which altitudewas the most significant contributor (r = 0793 p lt 001) followed by coarse particles (r = 0747p lt 001) and fine particles (r = acute0744 p lt 001) (Table 4) All physical factors except for fineparticles were in the opposite direction from the chemical variables (Figure 4c) This result suggeststhat the decline in altitude reflected deterioration in water quality accompanied by increases in organicmaterial and nutrients The heterogeneity of the macroinvertebrate habitats also decreased with thelongitudinal gradient toward downstream The second axis was negatively related with stream order(r =acute0658 p lt 001) and DO (r =acute0467 p lt 001) High positive scores with the first axis were denotedfor the rhithronic (ie pertaining to the headwaters) and intolerant species (eg Drunella aculea (Allen)E nipponicus Glossosoma sp R nigrocephala Iwata and H orientalis) whereas negative scores wereobserved for the potamic (ie pertaining to rivers) and tolerant taxa (eg Micronecta sedula HorvaacutethPhysa acuta Draparnaud Labiobaetis atrebatinus (Eaton) and Asellus hilgendorfii Bovalius) (Figure 4b)

4 Discussion

The Asian monsoon region is a global biodiversity hotspot suffering from increasinganthropogenic disturbances but aquatic biodiversity and ecosystem integrity remain poorlyexplored [3] This is the same situation in Korea but recent establishment of the National AquaticEcological Monitoring Program [36] opened a new era to assess ecosystem health and biodiversityin Korea Our work presented in this paper takes advantage of the opportunity of such anationwide scale of survey Although the five river watersheds in Korea exhibited differences in

Water 2016 8 27 13 of 20

environmental conditions and macroinvertebrate taxa abundance overall taxonomic compositionat each watershed displayed little difference (Table 2) Instead a considerable spatial variation inbenthic macroinvertebrate assemblages accounted for the combination of both ultimate (eg altitudeand the degree of land use) and proximate factors (eg flow stream bed substrate BOD EC andnutrients) This finding was in line with previous studies of benthic diatoms in Korea [25] andmacroinvertebrates in other Asian countries [1237] suggesting the importance of various multi-scalefactors in structuring macroinvertebrate assemblages [38] Our results provide basal information forthe sustainable management and conservation practices of stream ecosystems

41 Macroinvertebrate Taxonomic Composition

The macroinvertebrate assemblages in Korean stream ecosystems generally bear resemblance tothose in tropical and other temperate streams at higher taxonomic levels [3539] However temperateKorean streams were relatively rich in Ephemeroptera Diptera and Trichoptera when comparedwith tropical streams for the higher biodiversity of Gastropoda Decapoda and other insect orderssuch as Odonata and Hemiptera [3940] (Table 2) The taxonomic composition also included a largenumber of rhithronic fauna that prefer stony substrates For example Baetidae Heptageniidae andEphemerellidae mainly dominated the Ephemeroptera and Rhyacophilidae and Hydropsychidaecomposed the Trichoptera in this study

We confirmed a total of 340 macroinvertebrate taxa in this study Of the macroinvertebrate taxachironomid midge larvae and a small minnow mayfly (B fuscatus) were extensively encounteredthroughout Korean stream environments with the highest occurring frequency with 94 and 76of total sampling sites respectively Temperate Korean streams were also characterized with a fewpredominant colonizers and a majority of rare taxa in macroinvertebrate taxonomic compositionMoreover only six cosmopolitan taxa were noticeably comprised of gt60 of all macroinvertebratesamples which were L gotoi Chironomidae spp U punctisetae C brevilineata H valvata andH kozhantschikovi These dominant taxa were found to be significant indicators of mesotrophicor polytrophic streams in our study (Table 3) consistent with a result that most Korean streams andrivers were degraded in both chemical and biological status [36] On the other hand most Koreanstreams were occupied by a great number of rare macroinvertebrate species with a small distributionrange andor low abundance as was also demonstrated in other studies [4142]

42 Environmental Relationships with Macroinvertebrate Distribution

Benthic habitats are complex and a variety of environmental variables acting at multiple spatialscales regulate the composition and distribution patterns of stream macroinvertebrate assemblagesin an exclusive or synergistic fashion [3843] We revealed that the variables associated with altitudeand in-stream habitats best accounted for the largest amount of variability in our macroinvertebratedata set supporting the more important determinants of local environmental factors than broad orregional parameters [1644] The importance and role of local environmental variables have also beenhighlighted in other aquatic communities aquatic macrophytes [45] freshwater phytoplankton [46]benthic diatoms [44] intertidal macroinvertebrates [47] and fish [48] However a comprehensiveunderstanding of multispatial scales is needed because of significant correlations between macrohabitatand microhabitat characteristics depending on the relative size of the area studied [3]

In our study the variability among the macroinvertebrate-based stream groups was moreprominently explained by the altitudinal gradients together with streambed composition and watervelocity than chemical variables (Table 3) First the most widely accepted theory related to altitudinalchanges is the river continuum concept (RCC) which displays structural and functional responsesto the longitudinal gradient [49] Altitude has also been well documented in other studies as amain descriptor to determine macroinvertebrate richness as well as other environmental variablessuch as temperature hydrology food availability streambed condition and water chemistry [350]However we revealed poor relationships of altitude with water chemistry in contrast with significant

Water 2016 8 27 14 of 20

associations with physical variables and biological attributes such as taxa richness EPT richnessEPT abundance and the Shannon diversity index This may be due to the fact that over half ofthe studied streams corresponded to lowland streams below 100 m asl which were characterizedby moderate or slightly poor water quality with severe variations in BOD TN TP and Shannondiversity-based saprobity [3651] (Table 1) Harding et al [52] demonstrated that increasing humanland use intensity along a river continuum caused water quality degradation consequently leadingto changes in taxonomic composition from intolerant EPT dominated to tolerant taxa-dominatedassemblages despite a gradual increase in taxa abundance by a few dominant species

Riffle habitats are commonly characterized by shallow water depth oxygenating fast-flowingwater and stony beds and exhibit higher taxa richness and abundance than that at pools or habitatswith fine sediment as in our case [34253] Such hydraulic conditions are critical determinantsfor the distribution and species composition of benthic organisms [1654] and are the drivingforces for evolution of their morphologies and life history [11] Rheophilous (ie having an affinityfor running waters) and limnophilous taxa were clearly discriminated based on the correlationanalysis (Figure 2) and CCA (Figure 4) results For example well-known rhithronic species intwo Ephemeropteran (Ephemerellidae and Heptageniidae) and one Trichopteran (Hydropsychidae)families mostly displayed high preference to the mid- or fast current conditions which corresponds tothe intolerant scraper or filtering collector groups abundant in upper and middle stream reaches [49]Thus biological monitoring and assessment programs using rheophilic macroinvertebrates wouldbenefit from their ecological characteristics and their indication of good environmental quality(eg [42]) although seasonal fluctuations in hydraulic parameters by the Asian monsoon more criticallycause a catastrophic drift and washout of benthic organisms

Streambed composition is one of the most important factors to directly influence richness andabundance of macroinvertebrates on local scales [1216] thus close correlations would be expectedwith variables related to longitudinal changes in stream ecosystems Boulders and cobbles aretypically the major structural elements in steep gradient upper streams whereas sand and smallersediments predominate in the lower reaches [55] There have been a large number of studies onthe macroinvertebrate-substrate relationship most of which have revealed that macroinvertebratediversity and density increase with higher heterogeneity due to the available stable and diversemicrohabitats (eg [1043]) Therefore factors determining macroinvertebrate communities at localscales obviously put a priority on the streambed conditions rather than water quality or other physicalvariables We found that the mainstreams of the Nakdong River which contained about 60 fineparticles retained the lowest taxa richness (82 on average n = 18) and abundance (747 individualsm2)among five major rivers despite its good water quality condition (mean BOD 19 and TN 18 mgL)with the exception of the severely polluted Youngsan River (89 taxa richness and 73 BOD n = 13)These results indicate that homogeneous streambeds with greater fine particles support lower diversityand abundance even when streams maintain good water quality [56] Additionally organic pollutioncould transform the coarse substrate into an organic rich soft bottom altering the community structurefrom dominated by diverse and intolerant species to communities predominated by a few tolerantspecies [320] as in the case of the Youngsan River

43 Considerations to Improve Macroinvertebrate Biomonitoring Programs

Not until 2006 did Korea adopt biological water quality criteria and the concept of ecologicalintegrity in the water quality program [2536] Since then Korean government has led a biologicalsurvey of streams and rivers (ie NAEMP) every year to assess the current biological status of streamand river ecosystems and to develop a strategy for the restoration and management of disturbedsystems [25] As a part of a nationwide survey benthic macroinvertebrates are also monitored based onthe guidelines and assessment tools [27] Notwithstanding their suitability for convenient and rapidbio-assessment there remain debatable issues as to whether the methods for sampling and treating

Water 2016 8 27 15 of 20

macroinvertebrates are effective to provide a reliable and accurate indication of the macroinvertebratefauna throughout the country

The Korean national biomonitoring program presents field sampling in a cost-effective andtime-saving manner for rapid bio-assessment To satisfy this purpose benthic macroinvertebratesare optimized to be collected at riffle andor gliding run habitats using a Surber sampler with threereplicates [27] However such sampling methods probably underestimate overall biodiversity instream ecosystems considering the whole stream environment First single-habitat sampling possiblyproduces incomplete taxa lists and includes no target habitats at certain sites despite its advantagethat the influences of both water and habitat quality on macroinvertebrates are not confounded byinstream habitat variation [57] In this regard a multihabitat approach would be more profitablefor the estimation of taxonomic diversity due to its consistent application across stream typesespecially at large-scaled survey comprehensive taxa lists and effective assessment of ecologicalconditions [58] Second the Surber sampler is one of the most commonly used quantitative toolsin lotic systems and provides high-precision information on the abundance and composition ofmacroinvertebrate assemblages [2159] This method is on the other hand usually more appropriatefor riffle habitats of shallow streams presumably underestimating overall biodiversity in a regionRecent studies on the comparison between sampling devices suggested that artificial substrates(eg leaf-bags) would be used as complementary tools due to their discriminative taxonomiccomposition [60ndash62] Third a majority of biomonitoring programs widely adopt three to five replicatesfor lotic ecosystems because one way to reduce monitoring costs is to decrease the sample size [216364]The previous studies also showed that such a small number of replicates rarely influenced ecologicalhealth assessment particularly for the indices applying sensitivitytolerance taxa as the same forNAEMP [65ndash67] Nevertheless small sample sizes may influence the values of biological measuresand the representativeness for a real benthic community based on the asymptotic relationship ofthe number of taxa with both the sampling area and the collected individuals [68] Finally sievemesh size could also affect the accurate estimates of taxonomic diversity and environmental qualityassessment [67] Finer mesh sizes more accurately represent macroinvertebrate assemblages thancoarser mesh sizes whereas they need more efforts to handle specimens On the contrary coarsermesh sizes undervalue the original density and taxa richness of macroinvertebrate assemblages bypassing small individuals through the sieves and result in higher diversity [69] Considering thetradeoff between cost and effectiveness many rapid bio-assessments determine 05 mm mesh size as areasonable choice [216470] Therefore future researches are required for identifying optimal samplingeffort comprehensively considering cost-effectiveness easy applicability and well representative ofresident macroinvertebrate assemblages

5 Conclusions

Large-scale knowledge on environmental relationships of aquatic communities is crucial toconserve freshwater biodiversity and sustain ecological integrity Korean stream macroinvertebrateassemblages were determined not only by regional and physical instream variables but also bypollution-related parameters at nation-wide scale Macroinvertebrate-based site classification evidentlyprovided an environmental characterization for different types of Korean streams indicating thatbenthic macroinvertebrates are a valuable biomonitoring material The results of this study provideimportant information and a bridge for further work such as the assemblagemdashspecific responses toenvironmental disturbance Our results also contribute to establishing effective management practicesimplementing conservation measures and developing more reliable biological monitoring tools forsustainable freshwater ecosystems

Acknowledgments This study was performed under the project of ldquoNational Aquatic Ecosystem Health Surveyand Assessmentrdquo in Korea and was supported by the Ministry of Environment and the National Institute ofEnvironmental Research Korea The authors are grateful to survey members involved in the project The authorsalso thank the anonymous reviewers for their help in improving the scientific content of the manuscript

Water 2016 8 27 16 of 20

Author Contributions Yung-Chul Jun developed the concept of the study performed data analysis and wrotethe manuscript Nan-Young Kim assisted data processing and figure construction Sang-Hun Kim conductedquality assurance of the physico-chemical and biological data Young-Seuk Park and Dong-Soo Kong assistedstudy design and statistical analysis Soon-Jin Hwang supervised the research and assisted data interpretationand manuscript preparation All the authors contributed to the review of the manuscript

Conflicts of Interest The authors declare no conflict of interest

Appendix A

Table A1 Codes for macroinvertebrates contributing to more than 02 of total abundance for canonicalcorrespondence analysis in Figure 4

Code TaxonPhylum Platyhelminthes

DugSp Dugesia spPhylum Mollusca

SemLi Semisulcospira libertina (Gould)PhyAc Physa acuta Draparnaud

Phylum AnnelidaLimGo Limnodrilus gotoi HataiHirNi Hirudo nipponia Whitman

Phylum ArthropodaClass Crustacea

AseSp Asellus spGamSp Gammarus sp

Class Insecta

Order Ephemeroptera

BaeTu Baetiella tuberculata (Kazlauskas)BaeFu Baetis fuscatus (Linnaeus)BaeUr Baetis ursinus KazlauskasLabAt Labiobaetis atrebatinus (Eaton)NigBa Nigrobaetis bacillus (Kluge)EcdBa Ecdyonurus bajkovae KlugeEcdJo Ecdyonurus joernensis BengtssonEcdKi Ecdyonurus kibunensis ImanishiEcdLe Ecdyonurus levis (Navaacutes)EpeNi Epeorus nipponicus (Ueacuteno)EpeLa Epeorus latifolium (Ueacuteno)EpePe Epeorus pellucidus (Brodsky)ChoAl Choroterpes altioculus KlugeParJa Paraleptophlebia japonica (Matsumura)PotFo Potamanthus formosus EatonRhoCo Rhoenanthus coreanus (Yoon and Bae)DruAc Drunella aculea (Allen)EphOr Ephemera orientalis McLachlanSerSe Serratella setigera (Bajkova)UraPu Uracanthella punctisetae (Matsumura)CaeNi Caenis nishinoae Malzacher

Order Hemiptera

MicSe Micronecta sedula HorvaacutethMicSp Micronecta sp

Order Coleoptera

ElmSp Elmidae spEubKa Eubrianax KUaMatKa Mataeopsephus KUaPseKa Psephenoides KUa

Water 2016 8 27 17 of 20

Table A1 Cont

Code Taxon

Order Diptera

AntKa Antocha KUaCulSp Culex spChiSp Chironomidae spp (non-red type)ChiRe Chironomini spp (red-type)

Order Trichoptera

RhyNi Rhyacophila nigrocephala IwataHydKa Hydroptila KUaGloKa Glossosoma KUaCheBr Cheumatopsyche brevilineata IwataCheKa Cheumatopsyche KUaCheKb Cheumatopsyche KUbHydKo Hydropsyche kozhantschikovi MartynovHydKb Hydropsyche KUbHydOr Hydropsyche orientalis MartynovHydVa Hydropsyche valvata MartynovMacRa Macrostemum radiatum McLachlanPsySp Psychomyia sp

References

1 Dudgeon D Arthington AH Gessner MO Kawabata ZI Knowler DJ Leacutevecircque C Naiman RJPrieur-Richard AH Soto D Stiassny MLJ et al Freshwater biodiversity Importance threats status andconservation challenges Biol Rev 2006 81 163ndash182 [CrossRef] [PubMed]

2 Strayer DL Dudgeon D Freshwater biodiversity conservation Recent progress and future challengesJ N Am Benthol Soc 2010 29 344ndash358 [CrossRef]

3 Li F Chung N Bae M-J Kwon Y-S Park Y-S Relationships between stream macroinvertebrates andenvironmental variables at multiple spatial scales Freshwater Biol 2012 57 2107ndash2124 [CrossRef]

4 Dudgeon D The ecology of tropical Asian rivers and streams in relation to biodiversity conservationAnnu Rev Ecol Syst 2000 31 239ndash263 [CrossRef]

5 De Silva SS Abery NW Nguyen TTT Endemic freshwater finfish of Asia Distribution and conservationstatus Divers Distrib 2007 13 172ndash184 [CrossRef]

6 Voumlroumlsmarty CJ McIntyre PB Gessner MO Dudgeon D Prusevich A Green P Glidden S Bunn SESullivan CA Liermann CE et al Global threats to human water security and river biodiversity Nature2010 467 555ndash561 [CrossRef] [PubMed]

7 Strayer DL Challenges for freshwater invertebrate conservation J N Am Benthol Soc 2006 25 271ndash287[CrossRef]

8 Buss DF Baptista DF Silveira MP Nessimian JL Dorvilleacute LFM Influence of water chemistryand environmental degradation on macroinvertebrate assemblages in a river basin in south-east BrazilHydrobiologia 2002 481 125ndash136 [CrossRef]

9 Bott TL Brock JT Dunn CS Naiman RJ Ovink RW Petersen RC Benthic community metabolism infour temperate stream systems An inter-biome comparison and evaluation of the river continuum conceptHydrobiologia 1985 220 109ndash117 [CrossRef]

10 Merz JR Ochikubo Chan LK Effects of gravel augmentation on macroinvertebrate assemblages in aregulated California river River Res Appl 2005 21 61ndash74 [CrossRef]

11 Nelson SM Lieberman DM The influence of flow and other environmental factors on benthic invertebratesin the Sacramento River USA Hydrobiologia 2002 489 117ndash129 [CrossRef]

12 Jiang XM Xiong J Qiu JW Wu JM Wang JW Xie ZC Structure of macroinvertebrate communitiesin relation to environmental variables in a subtropical Asian river system Int Rev Hydrobiol 2010 95 42ndash57[CrossRef]

Water 2016 8 27 3 of 20

The entire stream system throughout South Korea comprises five watersheds including fivelarge rivers their tributaries and other small independent streams (Figure 1) Land use types in eachwatershed generally display well-managed forests upstream and agricultural and urban developmentfrom middle to lower regions Most Korean streams have suffered from a variety of human activitiesthat alter the physicochemical stream environments particularly caused by channel modification andeutrophication [24]

Among 720 sampling sites the largest number of sites belonged to the Han River watershed (HRW)(n = 320) followed by the Nakdong River watershed (NRW) (n = 130) the Geum River watershed(GRW) (n = 130) the Youngsan River watershed (YRW) (n = 76) and the Seomjin River watershed(SRW) (n = 64) It was assumed that such a nationwide survey covered the majority of stream types inKorea to understand how lotic macroinvertebrates are spatially distributed in relation to environmentalfactors Field sampling was conducted during spring (May 2009) under base flow conditions becausethe highest benthic macroinvertebrate diversity was expected at that time More information of thefive major river watersheds in Korea can be found in Hwang et al [25]

Figure 1 Geographic locations of the study sites Five macroinvertebrate-based site groups wereclassified as G1a (n = 126 black circles) G1b (n = 199 white circles) G2a (n = 106 white triangles) G2b(n = 118 gray triangles) and G2c (n = 171 black triangles) based on Soslashrenson distance measure clusteranalysis Dark lines indicate the five large rivers and the light lines display their tributaries and smallindependent streams

22 Measurement of Environmental Variables

Environmental variables were measured both in the field and in the laboratory to define theireffects on benthic macroinvertebrate assemblages Three categories of environmental variables were

Water 2016 8 27 4 of 20

considered such as watershed-related regional variables physical in-stream properties and waterquality elements

Altitude and land-use types were considered as regional variables for watershed characteristicsThe altitude at each sampling site was obtained using digital elevation data (Openmate Inc SeoulKorea) The proportion of prevalent land use types was determined for each sampling site using atopographic map (150000)

Physical in-stream properties were measured during field surveys (i) stream width for thedistance from bank to bank at a transect representative of the stream channel (ii) wetted stream widthusing a range finder (model LRM-1500M Newcon Optik Inc Toronto ON Canada) (iii) water depthof the vertical distance from the water surface to stream bottom (iv) current velocity at riffles or glidingruns using a current meter (3000-LX Swoffer Instruments Inc Tukwila WA USA) or calculated bythe Craig method [2627] (v) percent substrate composition visually estimated as fine (lt2 mm) andcoarse-sized particles (ě2 mm)

Water quality variables such as pH water temperature dissolved oxygen (DO) turbidity andelectrical conductivity (EC) were measured with a multi-probe portable meter (eg YSI 6920 YSI IncYellow Springs OH USA or Horiba U-22XD Kyoto Japan) at the center of each sampling stretch Twoliters of water samples were collected in sterilized plastic bottles at each site kept in a container withice and transported to the laboratory Laboratory measurements were conducted to determine thebiochemical oxygen demand (BOD) total nitrogen (TN) and total phosphorus (TP) following Standardmethods [28]

23 Sampling of Benthic Macroinvertebrate

A Surber sampler (30 cm ˆ 30 cm 1 mm mesh) was employed to collect benthicmacroinvertebrates Samplings were conducted at fast-flowing riffle or gliding run habitats (inthe case when suitable riffles were not available) within 100 m Quantitative samples were taken fromthree randomly selected riffles at each site pooled together in a 500 mL plastic bottle with 80 ethanoland labeled The sampling device and procedures followed the guidelines of the National AquaticEcological Monitoring Program (NAEMP) Korea [27]

After field sampling all organisms were hand-sorted from detritus and inorganic materialand stored in 70 ethanol Subsampling was permitted only for dominant taxonomic groups (egOligochaeta Ephemerellidae Chironomidae and Hydropsychidae) with large numbers of specimensavailable in each sample Each macroinvertebrate specimen was identified to the lowest possibletaxonomic level (usually genus or species) However several taxa with limited systematic information(eg Coleoptera and Diptera) were identified only to the family level All individuals were countedand converted to individualsm2

24 Data Analysis

Differences in environmental variables and macroinvertebrate assemblages were identified amongthe five major river watersheds by the KruskalndashWallis test followed by Dunnrsquos nonparametric multiplecomparison test if they are significantly different (p lt 005) Spearmanrsquos rank correlation analysiswas used to indicate the relationships between the most dominant taxa and environmental variablesA cluster analysis was conducted to classify the benthic macroinvertebrate communities using theflexible beta method (beta = acute025) with the Soslashrenson distance measure [29] Samples were classifiedinto clusters based on similarities in the community composition The multi-response permutationprocedure (MRPP [30]) which is a non-parametric method to test for differences in assemblagestructure among a priori defined groups [31] was conducted to evaluate differences among clustersDifferences in environmental variables among clusters were evaluated using the KruskalndashWallistest and Dunnrsquos nonparametric multiple comparison test The KruskalndashWallis test Dunnrsquos test andSpearman correlation analysis were performed with STATISTICA software (StatSoft Inc version 7Tulsa OK USA)

Water 2016 8 27 5 of 20

Indicator species analysis (IndVal [32]) was performed to evaluate potential indicator speciesin each cluster defined in advance The indicator value of a species is the product of its relativeabundance and frequency (ˆ 100) ranging from 0 (no indication) to 100 (perfect indication) [33]A perfect indicator of a particular group should be faithful and exclusive to that group never occurringin other groups [29] A species in a cluster that had an indicator value greater than in any othercluster was defined as good indicator species for that cluster in this study A Monte Carlo method wasperformed to test the significance of indicator values

Canonical correspondence analysis (CCA) was used to relate macroinvertebrate assemblages toenvironmental variables and to identify which environmental variables could best differentiate amongthe clusters [34] Monte-Carlo simulations were carried out to verify whether variables exerted asignificant effect (p lt 005) on macroinvertebrate distributions For the cluster analysis and CCA thosetaxa with less than 02 of total abundance were excluded to minimize the effects of rare taxa Taxaabundance data were transformed to log (x + 1) in both analyses to down-weight the effects of dominanttaxa Square-root-transformation was used for the environmental parameters expressed in percentages(eg type of land use and substrate composition) and the other variables were transformed to log(x + 1) except pH After these processes all environmental variables were rescaled in the range of0 and 1 based on the minimum-maximum range normalization [25] Spearman correlation coefficientsbetween scores and environmental variables were calculated to assist interpretation of changes incommunity profile using STATISTICA software (StatSoft Inc version 7 Tulsa OK USA) Clusteranalysis IndVal MRPP and CCA were conducted using PC-ORD software (ver 425 MjM SoftwareDesign Gleneden Beach OR USA) [34]

3 Results

31 Environmental Characteristics

Despite a large variation physicochemical factors were significantly different among watersheds(Table 1) On average the altitude percent forest and water velocity of the HRW and SRW werethe higher than the other watersheds The SRW streambeds were very heterogeneous with thehighest percentage of coarse-sized particles whereas those of the YRW contained a large amountof fine sediment High altitude fast water velocity and substrate complexity in both the HRW andSRW indicated good in-stream habitat conditions and potential to support high biodiversity andabundance of macroinvertebrates (Table 1a) The other three watersheds (NRW GRW and YRW) werecharacterized by low altitude and a high proportion of agricultural land use

Water quality parameters varied more prominently than physical variables among riverwatersheds (Table 1b) The average concentrations of DO BOD TN TP and turbidity were generallylower in the SRW than those in the other watersheds EC varied widely depending on the samplinglocation with the highest values near estuaries Nutrient-related factors were particularly high in theGRW YRW and HRW

32 Benthic Macroinvertebrate Assemblages

A total of 340 taxa belonging to 113 families in 23 orders of five phyla were identified in the fivemajor river watersheds during the survey Most of these were aquatic insects (272 species) including144 Ephemeroptera Plecoptera Trichoptera (EPT 62 mayflies 24 stoneflies and 58 caddisflies) taxaand 35 Dipteran species Taxa richness from the 720 sampling sites ranged from 0 to 49 with amean of 144 (˘ 91) with the highest diversity at HRW and the lowest in YRW (Table 2a) In contrasthomogeneous streambeds and nutrient enrichment attributed to relatively low Shannon diversity indexand high dominance index in both the NRW and YRW The proportion of EPT taxa richness rangedfrom 401 (GRW) to 548 (SRW) One-way ANOVA revealed that taxa abundance significantlydiffered among river watersheds at p lt 001 whereas there were no great differences for the relativeabundance of each taxonomic group among watersheds (Table 2b)

Water 2016 8 27 6 of 20

Table 1 Descriptive statistics of (a) regional and physical instream variables and (b) chemical variables in the five major river watersheds the Han River (HRW)Nakdong River (NRW) Geum River (GRW) Youngsan River (YRW) and Seomjin River Watershed (SRW) Top and bottom lines of each variable indicate theaverage with standard deviation (in parenthesis) and the range respectively KruskalndashWallis test (KndashW) was performed with the environmental variables to comparethe differences of each variable among river watersheds The same small letters indicate no significant difference based on Dunnrsquos multiple comparison testsAbbreviations DO dissolved oxygen BOD biochemical oxygen demand EC electrical conductivity TN total nitrogen TP total phosphorus

Variable HRW (n = 320) NRW (n = 130) GRW (n = 130) YRW (n = 76) SRW (n = 64) Total (n = 720) p (KndashW)

(a) Regional and physical instream variables

Altitude (m) 1475 (1516) d 896 (1191) bc 577 (612) ab 325 (351) a 1181 (793) cd 1061 (1262)000010ndash7210 10ndash6290 00ndash2780 00ndash2110 10ndash3350 00ndash7210

Urban317 (320) b 230 (308) ab 309 (358) b 314 (302) b 146 (124) a 284 (315)

00000ndash100 0ndash100 0ndash100 0ndash90 0ndash80 0ndash100

Agriculture 247 (275) a 425 (310) bc 466 (389) c 454 (307) c 359 (207) b 350 (317)00000ndash100 0ndash100 0ndash100 0ndash90 0ndash80 0ndash100

Forest358 (332) b 314 (278) b 179 (301) a 226 (243) a 488 (246) c 315 (313)

00000ndash100 0ndash100 0ndash100 0ndash100 0ndash95 0ndash100

Water velocity (cms) 538 (279) c 147 (140) a 381 (345) b 177 (131) a 419 (260) b 390 (304)000000ndash1400 00ndash670 00ndash1377 04ndash475 14ndash982 00ndash1400

Fine particles 311 (279) b 365 (368) bc 436 (345) c 547 (313) d 108 (229) a 350 (326)000000ndash1000 00ndash1000 00ndash1000 00ndash1000 00ndash1000 00ndash1000

Coarse particles 686 (281) c 635 (368) bc 564 (345) b 453 (313) a 892 (229) d 648 (327)000000ndash1000 00ndash1000 00ndash1000 00ndash1000 00ndash1000 00ndash1000

(b) Chemical variables

pH 81 (08) bc 80 (08) ab 83 (09) c 80 (07) ab 78 (07) a 81 (08)000365ndash101 62ndash106 70ndash111 67ndash101 67ndash96 62ndash111

DO (mgL) 978 (247) a 1081 (236) b 1086 (336) b 1006 (169) a 957 (132) a 1017 (254)0000242ndash1610 255ndash1734 274ndash1786 619ndash1540 711ndash1269 242ndash1786

BOD (mgL) 31 (37) bc 19 (13) a 37 (20) c 35 (30) bc 27 (17) b 30 (29)000003ndash375 04ndash104 08ndash91 03ndash133 03ndash123 03ndash375

EC (microScm)2998 (3376) a 13587 (60671) b 4048 (3498) a 2707 (4026) a 12846 (58234) b 5944 (31416)

0000103ndash27290 197ndash440000 861ndash27800 285ndash30820 326ndash333600 103ndash440000

TN (mgL) 315 (297) b 210 (166) a 360 (242) b 336 (359) b 232 (139) a 299 (269)0000038ndash2378 032ndash1130 029ndash1427 069ndash2771 044ndash577 029ndash2771

TP (mgL) 015 (041) bc 007 (015) ab 014 (015) bc 021 (028) c 005 (006) a 013 (030)0000000ndash559 000ndash091 001ndash101 001ndash166 000ndash032 000ndash559

Turbidity (NTU) 93 (166) b 86 (74) b 139 (223) b 78 (459) b 21 (33) a 92 (212)000000ndash1520 00ndash342 04ndash1824 00ndash4000 00ndash169 00ndash4000

Water 2016 8 27 7 of 20

Table 2 Assemblage attributes (a) and average abundance (individualsuml macute2) (b) of benthic macroinvertebrates with standard deviation (in parenthesis) in fivemajor river watersheds the Han River (HRW) Nakdong River (NRW) Geum River (GRW) Youngsan River (YRW) and Seomjin River Watershed (SRW) Relativeabundance (RA) indicated as an average of total density for each taxonomic group KruskalndashWallis test (KndashW) was performed for each taxonomic group The samesmall letters indicate no significant difference based on Dunnrsquos multiple comparison test

Biological Attributes HRW (n = 320) NRW (n = 130) GRW (n = 130) YRW (n = 76) SRW (n = 64) Total (n = 720) RA p (KndashW)

(a) Assemblage attributes

Taxa richness 157 (94) a 117 (73) b 155 (108) a 106 (63) b 151 (80) a 144 (91) - 0000EPT richness 103 (80) c 53 (55) a 76 (82) b 45 (47) a 85 (54) b 81 (75) - 0000

Taxa abundance 28675 (97919) b 8649 (10352) a 39444 (59647) b 9470 (10541) a 6120 (5482) a 22971 (71210) - 0000EPT abundance 10669 (17029) b 3032 (7265) a 15525 (24410) c 3164 (5450) a 2786 (3158) a 8674 (16472) - 0000

Dominance index 065 (021) b 070 (020) bc 071 (021) bc 073 (020) c 052 (023) a 067 (022) - 0000Shannon diversity index 233 (100) b 208 (091) b 209 (102) b 179 (094) a 263 (109) c 221 (101) - 0000

(b) Taxa abundance of higher taxonomic group

Non-Insecta

Platyhelminthes 187 (788) 287 (1967) 255 (1024) 99 (492) 172 (378) 207 (1096) 001 0447Nematomorpha 02 (09) 01 (06) 01 (05) 01 (08) 00 (00) 01 (07) 000 0082

Mollusca 107 (394) a 444 (1515) c 304 (543) b 274 (495) b 212 (309) ab 230 (765) 001 0000Annelida 6035 (68262) b 399 (908) a 5483 (29976) b 210 (614) a 681 (917) a 3827 (47310) 020 0000Crustacea 19 (122) a 429 (2143) a 412 (2439) a 1098 (5606) b 14 (70) a 277 (2306) 001 0000

Insecta

Ephemeroptera 6926 (11329) b 3166 (5946) a 5651 (10151) b 1990 (3087) a 3773 (3890) a 5215 (9360) 027 0000Odonata 39 (123) a 42 (124) a 145 (371) b 119 (292) b 07 (22) a 64 (213) 000 0000

Plecoptera 66 (216) b 56 (296) b 42 (215) ab 01 (07) a 07 (42) a 48 (213) 000 0000Hemiptera 11 (93) a 387 (2074) b 250 (1291) ab 255 (2135) ab 00 (03) a 147 (1257) 001 0000

Megaloptera 26 (104) b 12 (60) ab 16 (60) ab 05 (23) a 10 (98) ab 18 (84) 000 0000Coleoptera 153 (976) a 286 (806) a 809 (2008) c 89 (315) a 569 (949) b 326 (1193) 002 0000

Diptera 4493 (7802) b 3098 (4521) b 8062 (18533) c 3441 (7121) b 1050 (1644) a 4469 (10095) 023 0000Trichoptera 5492 (10290) b 3066 (7718) a 8453 (15644) c 1145 (2962) a 1264 (2951) a 4754 (10448) 024 0000Lepidoptera 00 (01) a - 01 (09) b 00 (06) ab - 00 (04) 000 0000Neuroptera - - - 00 (03) - 00 (01) 000 0076

Water 2016 8 27 8 of 20

Korean stream ecosystems were characterized by a few predominant colonizers and a majority ofrare taxa in macroinvertebrate assemblage composition The most abundant and widespread taxa werea worm (Limnodrilus gotoi Hatai) and midge larvae (Chironomidae spp) with their relative abundanceof approximately 50 of total density throughout the whole river watershed Other dominant specieswere mayflies (ie Baetis fuscatus (Linnaeus) Epeorus pellucidus (Brodsky) and Uracanthella punctisetae(Matsumura)) and netspinning caddisflies (Cheumatopsyche brevilineata Iwata Hydropsyche valvataMartynov and Hydropsyche kozhantschikovi Martynov) among the different stream and river systemsmost of which were dominant in somewhat nutrient-rich habitats at middle or lower streams Howeverover 50 (195 taxa) of the fauna was present with low occurring frequency (less than 2 of all sites)and 90 with low abundance (less than 02)

The environmental relationships of the dominant taxa were stronger with the physical variables(ie altitude water velocity and streambed conditions) than with the chemical variables among whichwater velocity was the most significant parameter Consequently significant positive relationshipsexisted in most dominant taxa with peak abundance at a moderate velocity of 50ndash100 cms particularlyfor E pellucidus (r = 0410 p lt 0001) and C brevilineata (r = 0435 p lt 0001) (Figure 2) Baetiella tuberculata(Kazlauskas) U punctisetae and H valvata tended to occur in their highest densities at the fast velocity(120ndash140 cms) No clear tendency was observed for Chironomidae spp

Figure 2 Distribution patterns of dominant macroinvertebrates along with water velocity Data aregiven as arithmetic means with standard deviation Spearmanrsquos rank correlation coefficients betweenwater velocity and abundance of each dominant species are included (a) Uracanthella punctisetae(b) Epeorus pellucidus (c) Baetiella tuberculata (d) Chironomini sp (e) Cheumatopsyche brevilineata(f) Hydropsyche valvata

Water 2016 8 27 9 of 20

33 Macroinvertebrate-Based Site Classification

The cluster analysis based on the similarity in the benthic macroinvertebrate composition largelyclassified the 720 sampling sites into two clusters and subsequently sub-clustered them into five groupsAs a result 126 sampling sites were included in Group 1a 199 sites in Groups 1b 106 sites in Group 2a118 sites in Group 2b and 171 sites in Group 2c (Figure 1) MRPP validated these five groups withsignificant differences (A = 0484 p lt 0001) The differences in environmental variables among theclusters are shown in Figure 3 The most important indicator taxa for each cluster are shown with theirindicator values in Table 3

Figure 3 Distribution of selected environmental variables among the five clusters of the 720 samplingsites which were identified by cluster analysis with Soslashrenson distance measure Box represents the25th and 75th percentiles and whiskers indicate the 5th and 95th percentiles with standard deviations(error bar) The mean (horizontal dotted line) and median (horizontal solid line) are shown in each boxDifferent small letters indicate significant difference based on a Dunnrsquos multiple comparison test atp lt 005

Water 2016 8 27 10 of 20

Table 3 Indicator values () for the most important species (p lt 005) in each cluster group MonteCarlo tests (999 permutations) were used to assess the significance of each species as an indicator forthe respective group (G1andashG2c) In total 50 species whose contribution to total density was higher than02 were analyzed Less important species were not shown in this table

TaxaCluster Group

pG1a G1b G2a G2b G2c

Rhyacophila nigrocephala Iwata 47 16 0 0 0 0001Epeorus nipponicus (Ueacuteno) 46 1 0 0 0 0001Glossosoma KUa 44 4 0 0 0 0001Drunella aculea (Allen) 44 1 0 0 0 0001Hydropsyche orientalis Martynov 40 7 1 1 0 0001

Uracanthella punctisetae(Matsumura)

21 48 6 6 0 0001

Hydropsyche valvata Martynov 6 46 2 9 0 0001Cheumatopsyche brevilineataIwata

15 41 5 10 0 0001

Hydropsyche kozhantschikoviMartynov

21 40 3 16 0 0001

Psychomyia sp 0 32 1 5 0 0001

Ephemera orientalis McLachlan 2 20 41 5 2 0001Ecdyonurus levis (Navaacutes) 5 28 40 1 0 0001Ecdyonurus joernensis Bengtsson 0 12 25 1 0 0001Mataeopsephus KUa 0 16 23 0 0 0001Asellus sp 0 2 11 3 6 0001

Hirudo nipponia Whitman 1 10 2 28 4 0001Chironomini sp 1 7 9 27 21 0001Limnodrilus gotoi Hatai 5 12 18 23 9 0001

Micronecta sedula Horvaacuteth 0 0 0 0 20 0001Physa acuta Draparnaud 2 3 2 12 16 0001Micronecta sp 0 0 5 0 5 0007

Total number of significantindicator species

12 21 8 3 3 -

Each cluster was clearly differentiated according to the differences of instream physicochemicalconditions and geographical location of sampling sites The cluster analysis discriminated less pollutedstreams with low EC and fast flowing water (Group 1) from moderately or severely polluted steams withhigh EC and slow water velocity (Group 2) Group 1a (G1a) congregating in the HRW consisted specificallyof mountainous upper streams although a tenth of this group was scattered over the other watershedsexcept the YRW This group consisted of oligotrophic streams with distinguishing features of the highestaltitude the lowest BOD and nutrient concentrations and the fastest water velocity Additionally thecatchment was predominantly comprised of forested area The best indicator species for this group werecharacterized as high sensitivity against organic pollution (eg Rhyacophila nigrocephala Iwata Epeorusnipponicus (Ueacuteno) Drunella aculea (Allen) and Hydropsyche orientalis Martynov) Group 1b (G1b) containedthe largest number of sampling sites and was widely distributed throughout all river watersheds butmostly encompassing the agricultural and forested catchment G1a and G1b closely resembled chemicalenvironments but steam sites belonging to G1b displayed mesotrophic condition with slightly higherBOD and nutrients than those of G1a There existed the largest number of indicator species in G1b amongwhich U punctisetae showed the highest indicator value

G2a mostly included sites located in middle reaches of large rivers and their tributariesparticularly in the NRW and SRW Although Group 2a (G2a) was similar in overall environmentalcharacteristics to G1b G2a was characterized with slightly lower altitude higher EC and a lower watervelocity when compared with G1b Sampling sites suffering from poor water quality with organicdegradation and nutrient enrichment were confined to Group 2b with the highest BOD TN and TPconcentrations These sites were influenced by the highest degree of agriculture andor urbanizationThe significant indicator species of this group were Hirudo nipponia Whitman Chironomini sp and

Water 2016 8 27 11 of 20

L gotoi indicating high trophy and saprobity [35] Water quality conditions in Group 2c (G2c) were aspoor as those of G2b with the highest EC Sites in this group were characterized with the lowest watervelocity and the largest proportion of fine particles because G2c was gathered by streams adjacent toestuaries large rivers and dammed streams The only three weak indicator species appeared in G2c

34 Environmental Variables Affecting Macroinvertebrate Distributions

A CCA was performed to understand how macroinvertebrates were distributed alongenvironmental gradients (Figure 4) Total variability explained in the species data was 159 (Table 4)The eigenvalues of the first CCA axis (0281) and the second CCA axis (0101) were significant (p lt 00199 Monte Carlo permutation test) All three CCA results were significant based on a Monte Carlopermutation test (p lt 001)

Figure 4 Ordination plots constructed by canonical correspondence analysis for all sampling sites(n = 720) The plots present the ordination of sampling sites (a) and macroinvertebrates (b) with relativecontributions of environmental variables (c) for the first two axes Only species contributing gt02to total abundance were included The summary of ordination results is presented in Table 4 and thecodes for each taxon are shown in Appendix Table A1

Water 2016 8 27 12 of 20

Table 4 Spearmanrsquos rank correlation coefficients and probabilities of environmental variables andthe CCA axes ( p lt 001 p lt 005) (a) and summary of CCA results (n = 720) (b) All axes weresignificant based on Monte Carlo permutation procedures

Variables Axis 1 Axis 2 Axis 3

(a) Correlation coefficients

Altitude 0793 0236 0013Stream order acute0105 acute0658 0099

Urban acute0218 0134 acute0317 Agriculture acute0199 acute0273 0133

Forest 0504 0055 0266 Water velocity 0662 acute0054 acute0510

Fine particles acute0744 0325 acute0076 Coarse particles 0747 acute0327 0075

pH 0011 acute0236 0007DO 0304 acute0467 acute0166

BOD acute0550 0164 acute0370 EC acute0196 acute0278 acute0116 TN acute0463 0266 acute0387 TP acute0373 0229 acute0314

(b) Summary of CCA results

Eigenvalue 0281 0101 0073 variance explained in

taxa data 98 35 25

Cumulative varianceexplained 98 133 159

p value 0010 0010 0010

Total variance 2869 - -

The five clusters were well separated in the CCA ordination plot (Figure 4a) Both the G1aand G1b groups with good physicochemical environments were positioned on the right side of theordination plot and G2b and G2c were on the opposite side However the G2a group straddledboth sides Eight environmental variables (ie BOD TN TP altitude water velocity forest fineparticles and coarse particles) had significant correlations with the first axis among which altitudewas the most significant contributor (r = 0793 p lt 001) followed by coarse particles (r = 0747p lt 001) and fine particles (r = acute0744 p lt 001) (Table 4) All physical factors except for fineparticles were in the opposite direction from the chemical variables (Figure 4c) This result suggeststhat the decline in altitude reflected deterioration in water quality accompanied by increases in organicmaterial and nutrients The heterogeneity of the macroinvertebrate habitats also decreased with thelongitudinal gradient toward downstream The second axis was negatively related with stream order(r =acute0658 p lt 001) and DO (r =acute0467 p lt 001) High positive scores with the first axis were denotedfor the rhithronic (ie pertaining to the headwaters) and intolerant species (eg Drunella aculea (Allen)E nipponicus Glossosoma sp R nigrocephala Iwata and H orientalis) whereas negative scores wereobserved for the potamic (ie pertaining to rivers) and tolerant taxa (eg Micronecta sedula HorvaacutethPhysa acuta Draparnaud Labiobaetis atrebatinus (Eaton) and Asellus hilgendorfii Bovalius) (Figure 4b)

4 Discussion

The Asian monsoon region is a global biodiversity hotspot suffering from increasinganthropogenic disturbances but aquatic biodiversity and ecosystem integrity remain poorlyexplored [3] This is the same situation in Korea but recent establishment of the National AquaticEcological Monitoring Program [36] opened a new era to assess ecosystem health and biodiversityin Korea Our work presented in this paper takes advantage of the opportunity of such anationwide scale of survey Although the five river watersheds in Korea exhibited differences in

Water 2016 8 27 13 of 20

environmental conditions and macroinvertebrate taxa abundance overall taxonomic compositionat each watershed displayed little difference (Table 2) Instead a considerable spatial variation inbenthic macroinvertebrate assemblages accounted for the combination of both ultimate (eg altitudeand the degree of land use) and proximate factors (eg flow stream bed substrate BOD EC andnutrients) This finding was in line with previous studies of benthic diatoms in Korea [25] andmacroinvertebrates in other Asian countries [1237] suggesting the importance of various multi-scalefactors in structuring macroinvertebrate assemblages [38] Our results provide basal information forthe sustainable management and conservation practices of stream ecosystems

41 Macroinvertebrate Taxonomic Composition

The macroinvertebrate assemblages in Korean stream ecosystems generally bear resemblance tothose in tropical and other temperate streams at higher taxonomic levels [3539] However temperateKorean streams were relatively rich in Ephemeroptera Diptera and Trichoptera when comparedwith tropical streams for the higher biodiversity of Gastropoda Decapoda and other insect orderssuch as Odonata and Hemiptera [3940] (Table 2) The taxonomic composition also included a largenumber of rhithronic fauna that prefer stony substrates For example Baetidae Heptageniidae andEphemerellidae mainly dominated the Ephemeroptera and Rhyacophilidae and Hydropsychidaecomposed the Trichoptera in this study

We confirmed a total of 340 macroinvertebrate taxa in this study Of the macroinvertebrate taxachironomid midge larvae and a small minnow mayfly (B fuscatus) were extensively encounteredthroughout Korean stream environments with the highest occurring frequency with 94 and 76of total sampling sites respectively Temperate Korean streams were also characterized with a fewpredominant colonizers and a majority of rare taxa in macroinvertebrate taxonomic compositionMoreover only six cosmopolitan taxa were noticeably comprised of gt60 of all macroinvertebratesamples which were L gotoi Chironomidae spp U punctisetae C brevilineata H valvata andH kozhantschikovi These dominant taxa were found to be significant indicators of mesotrophicor polytrophic streams in our study (Table 3) consistent with a result that most Korean streams andrivers were degraded in both chemical and biological status [36] On the other hand most Koreanstreams were occupied by a great number of rare macroinvertebrate species with a small distributionrange andor low abundance as was also demonstrated in other studies [4142]

42 Environmental Relationships with Macroinvertebrate Distribution

Benthic habitats are complex and a variety of environmental variables acting at multiple spatialscales regulate the composition and distribution patterns of stream macroinvertebrate assemblagesin an exclusive or synergistic fashion [3843] We revealed that the variables associated with altitudeand in-stream habitats best accounted for the largest amount of variability in our macroinvertebratedata set supporting the more important determinants of local environmental factors than broad orregional parameters [1644] The importance and role of local environmental variables have also beenhighlighted in other aquatic communities aquatic macrophytes [45] freshwater phytoplankton [46]benthic diatoms [44] intertidal macroinvertebrates [47] and fish [48] However a comprehensiveunderstanding of multispatial scales is needed because of significant correlations between macrohabitatand microhabitat characteristics depending on the relative size of the area studied [3]

In our study the variability among the macroinvertebrate-based stream groups was moreprominently explained by the altitudinal gradients together with streambed composition and watervelocity than chemical variables (Table 3) First the most widely accepted theory related to altitudinalchanges is the river continuum concept (RCC) which displays structural and functional responsesto the longitudinal gradient [49] Altitude has also been well documented in other studies as amain descriptor to determine macroinvertebrate richness as well as other environmental variablessuch as temperature hydrology food availability streambed condition and water chemistry [350]However we revealed poor relationships of altitude with water chemistry in contrast with significant

Water 2016 8 27 14 of 20

associations with physical variables and biological attributes such as taxa richness EPT richnessEPT abundance and the Shannon diversity index This may be due to the fact that over half ofthe studied streams corresponded to lowland streams below 100 m asl which were characterizedby moderate or slightly poor water quality with severe variations in BOD TN TP and Shannondiversity-based saprobity [3651] (Table 1) Harding et al [52] demonstrated that increasing humanland use intensity along a river continuum caused water quality degradation consequently leadingto changes in taxonomic composition from intolerant EPT dominated to tolerant taxa-dominatedassemblages despite a gradual increase in taxa abundance by a few dominant species

Riffle habitats are commonly characterized by shallow water depth oxygenating fast-flowingwater and stony beds and exhibit higher taxa richness and abundance than that at pools or habitatswith fine sediment as in our case [34253] Such hydraulic conditions are critical determinantsfor the distribution and species composition of benthic organisms [1654] and are the drivingforces for evolution of their morphologies and life history [11] Rheophilous (ie having an affinityfor running waters) and limnophilous taxa were clearly discriminated based on the correlationanalysis (Figure 2) and CCA (Figure 4) results For example well-known rhithronic species intwo Ephemeropteran (Ephemerellidae and Heptageniidae) and one Trichopteran (Hydropsychidae)families mostly displayed high preference to the mid- or fast current conditions which corresponds tothe intolerant scraper or filtering collector groups abundant in upper and middle stream reaches [49]Thus biological monitoring and assessment programs using rheophilic macroinvertebrates wouldbenefit from their ecological characteristics and their indication of good environmental quality(eg [42]) although seasonal fluctuations in hydraulic parameters by the Asian monsoon more criticallycause a catastrophic drift and washout of benthic organisms

Streambed composition is one of the most important factors to directly influence richness andabundance of macroinvertebrates on local scales [1216] thus close correlations would be expectedwith variables related to longitudinal changes in stream ecosystems Boulders and cobbles aretypically the major structural elements in steep gradient upper streams whereas sand and smallersediments predominate in the lower reaches [55] There have been a large number of studies onthe macroinvertebrate-substrate relationship most of which have revealed that macroinvertebratediversity and density increase with higher heterogeneity due to the available stable and diversemicrohabitats (eg [1043]) Therefore factors determining macroinvertebrate communities at localscales obviously put a priority on the streambed conditions rather than water quality or other physicalvariables We found that the mainstreams of the Nakdong River which contained about 60 fineparticles retained the lowest taxa richness (82 on average n = 18) and abundance (747 individualsm2)among five major rivers despite its good water quality condition (mean BOD 19 and TN 18 mgL)with the exception of the severely polluted Youngsan River (89 taxa richness and 73 BOD n = 13)These results indicate that homogeneous streambeds with greater fine particles support lower diversityand abundance even when streams maintain good water quality [56] Additionally organic pollutioncould transform the coarse substrate into an organic rich soft bottom altering the community structurefrom dominated by diverse and intolerant species to communities predominated by a few tolerantspecies [320] as in the case of the Youngsan River

43 Considerations to Improve Macroinvertebrate Biomonitoring Programs

Not until 2006 did Korea adopt biological water quality criteria and the concept of ecologicalintegrity in the water quality program [2536] Since then Korean government has led a biologicalsurvey of streams and rivers (ie NAEMP) every year to assess the current biological status of streamand river ecosystems and to develop a strategy for the restoration and management of disturbedsystems [25] As a part of a nationwide survey benthic macroinvertebrates are also monitored based onthe guidelines and assessment tools [27] Notwithstanding their suitability for convenient and rapidbio-assessment there remain debatable issues as to whether the methods for sampling and treating

Water 2016 8 27 15 of 20

macroinvertebrates are effective to provide a reliable and accurate indication of the macroinvertebratefauna throughout the country

The Korean national biomonitoring program presents field sampling in a cost-effective andtime-saving manner for rapid bio-assessment To satisfy this purpose benthic macroinvertebratesare optimized to be collected at riffle andor gliding run habitats using a Surber sampler with threereplicates [27] However such sampling methods probably underestimate overall biodiversity instream ecosystems considering the whole stream environment First single-habitat sampling possiblyproduces incomplete taxa lists and includes no target habitats at certain sites despite its advantagethat the influences of both water and habitat quality on macroinvertebrates are not confounded byinstream habitat variation [57] In this regard a multihabitat approach would be more profitablefor the estimation of taxonomic diversity due to its consistent application across stream typesespecially at large-scaled survey comprehensive taxa lists and effective assessment of ecologicalconditions [58] Second the Surber sampler is one of the most commonly used quantitative toolsin lotic systems and provides high-precision information on the abundance and composition ofmacroinvertebrate assemblages [2159] This method is on the other hand usually more appropriatefor riffle habitats of shallow streams presumably underestimating overall biodiversity in a regionRecent studies on the comparison between sampling devices suggested that artificial substrates(eg leaf-bags) would be used as complementary tools due to their discriminative taxonomiccomposition [60ndash62] Third a majority of biomonitoring programs widely adopt three to five replicatesfor lotic ecosystems because one way to reduce monitoring costs is to decrease the sample size [216364]The previous studies also showed that such a small number of replicates rarely influenced ecologicalhealth assessment particularly for the indices applying sensitivitytolerance taxa as the same forNAEMP [65ndash67] Nevertheless small sample sizes may influence the values of biological measuresand the representativeness for a real benthic community based on the asymptotic relationship ofthe number of taxa with both the sampling area and the collected individuals [68] Finally sievemesh size could also affect the accurate estimates of taxonomic diversity and environmental qualityassessment [67] Finer mesh sizes more accurately represent macroinvertebrate assemblages thancoarser mesh sizes whereas they need more efforts to handle specimens On the contrary coarsermesh sizes undervalue the original density and taxa richness of macroinvertebrate assemblages bypassing small individuals through the sieves and result in higher diversity [69] Considering thetradeoff between cost and effectiveness many rapid bio-assessments determine 05 mm mesh size as areasonable choice [216470] Therefore future researches are required for identifying optimal samplingeffort comprehensively considering cost-effectiveness easy applicability and well representative ofresident macroinvertebrate assemblages

5 Conclusions

Large-scale knowledge on environmental relationships of aquatic communities is crucial toconserve freshwater biodiversity and sustain ecological integrity Korean stream macroinvertebrateassemblages were determined not only by regional and physical instream variables but also bypollution-related parameters at nation-wide scale Macroinvertebrate-based site classification evidentlyprovided an environmental characterization for different types of Korean streams indicating thatbenthic macroinvertebrates are a valuable biomonitoring material The results of this study provideimportant information and a bridge for further work such as the assemblagemdashspecific responses toenvironmental disturbance Our results also contribute to establishing effective management practicesimplementing conservation measures and developing more reliable biological monitoring tools forsustainable freshwater ecosystems

Acknowledgments This study was performed under the project of ldquoNational Aquatic Ecosystem Health Surveyand Assessmentrdquo in Korea and was supported by the Ministry of Environment and the National Institute ofEnvironmental Research Korea The authors are grateful to survey members involved in the project The authorsalso thank the anonymous reviewers for their help in improving the scientific content of the manuscript

Water 2016 8 27 16 of 20

Author Contributions Yung-Chul Jun developed the concept of the study performed data analysis and wrotethe manuscript Nan-Young Kim assisted data processing and figure construction Sang-Hun Kim conductedquality assurance of the physico-chemical and biological data Young-Seuk Park and Dong-Soo Kong assistedstudy design and statistical analysis Soon-Jin Hwang supervised the research and assisted data interpretationand manuscript preparation All the authors contributed to the review of the manuscript

Conflicts of Interest The authors declare no conflict of interest

Appendix A

Table A1 Codes for macroinvertebrates contributing to more than 02 of total abundance for canonicalcorrespondence analysis in Figure 4

Code TaxonPhylum Platyhelminthes

DugSp Dugesia spPhylum Mollusca

SemLi Semisulcospira libertina (Gould)PhyAc Physa acuta Draparnaud

Phylum AnnelidaLimGo Limnodrilus gotoi HataiHirNi Hirudo nipponia Whitman

Phylum ArthropodaClass Crustacea

AseSp Asellus spGamSp Gammarus sp

Class Insecta

Order Ephemeroptera

BaeTu Baetiella tuberculata (Kazlauskas)BaeFu Baetis fuscatus (Linnaeus)BaeUr Baetis ursinus KazlauskasLabAt Labiobaetis atrebatinus (Eaton)NigBa Nigrobaetis bacillus (Kluge)EcdBa Ecdyonurus bajkovae KlugeEcdJo Ecdyonurus joernensis BengtssonEcdKi Ecdyonurus kibunensis ImanishiEcdLe Ecdyonurus levis (Navaacutes)EpeNi Epeorus nipponicus (Ueacuteno)EpeLa Epeorus latifolium (Ueacuteno)EpePe Epeorus pellucidus (Brodsky)ChoAl Choroterpes altioculus KlugeParJa Paraleptophlebia japonica (Matsumura)PotFo Potamanthus formosus EatonRhoCo Rhoenanthus coreanus (Yoon and Bae)DruAc Drunella aculea (Allen)EphOr Ephemera orientalis McLachlanSerSe Serratella setigera (Bajkova)UraPu Uracanthella punctisetae (Matsumura)CaeNi Caenis nishinoae Malzacher

Order Hemiptera

MicSe Micronecta sedula HorvaacutethMicSp Micronecta sp

Order Coleoptera

ElmSp Elmidae spEubKa Eubrianax KUaMatKa Mataeopsephus KUaPseKa Psephenoides KUa

Water 2016 8 27 17 of 20

Table A1 Cont

Code Taxon

Order Diptera

AntKa Antocha KUaCulSp Culex spChiSp Chironomidae spp (non-red type)ChiRe Chironomini spp (red-type)

Order Trichoptera

RhyNi Rhyacophila nigrocephala IwataHydKa Hydroptila KUaGloKa Glossosoma KUaCheBr Cheumatopsyche brevilineata IwataCheKa Cheumatopsyche KUaCheKb Cheumatopsyche KUbHydKo Hydropsyche kozhantschikovi MartynovHydKb Hydropsyche KUbHydOr Hydropsyche orientalis MartynovHydVa Hydropsyche valvata MartynovMacRa Macrostemum radiatum McLachlanPsySp Psychomyia sp

References

1 Dudgeon D Arthington AH Gessner MO Kawabata ZI Knowler DJ Leacutevecircque C Naiman RJPrieur-Richard AH Soto D Stiassny MLJ et al Freshwater biodiversity Importance threats status andconservation challenges Biol Rev 2006 81 163ndash182 [CrossRef] [PubMed]

2 Strayer DL Dudgeon D Freshwater biodiversity conservation Recent progress and future challengesJ N Am Benthol Soc 2010 29 344ndash358 [CrossRef]

3 Li F Chung N Bae M-J Kwon Y-S Park Y-S Relationships between stream macroinvertebrates andenvironmental variables at multiple spatial scales Freshwater Biol 2012 57 2107ndash2124 [CrossRef]

4 Dudgeon D The ecology of tropical Asian rivers and streams in relation to biodiversity conservationAnnu Rev Ecol Syst 2000 31 239ndash263 [CrossRef]

5 De Silva SS Abery NW Nguyen TTT Endemic freshwater finfish of Asia Distribution and conservationstatus Divers Distrib 2007 13 172ndash184 [CrossRef]

6 Voumlroumlsmarty CJ McIntyre PB Gessner MO Dudgeon D Prusevich A Green P Glidden S Bunn SESullivan CA Liermann CE et al Global threats to human water security and river biodiversity Nature2010 467 555ndash561 [CrossRef] [PubMed]

7 Strayer DL Challenges for freshwater invertebrate conservation J N Am Benthol Soc 2006 25 271ndash287[CrossRef]

8 Buss DF Baptista DF Silveira MP Nessimian JL Dorvilleacute LFM Influence of water chemistryand environmental degradation on macroinvertebrate assemblages in a river basin in south-east BrazilHydrobiologia 2002 481 125ndash136 [CrossRef]

9 Bott TL Brock JT Dunn CS Naiman RJ Ovink RW Petersen RC Benthic community metabolism infour temperate stream systems An inter-biome comparison and evaluation of the river continuum conceptHydrobiologia 1985 220 109ndash117 [CrossRef]

10 Merz JR Ochikubo Chan LK Effects of gravel augmentation on macroinvertebrate assemblages in aregulated California river River Res Appl 2005 21 61ndash74 [CrossRef]

11 Nelson SM Lieberman DM The influence of flow and other environmental factors on benthic invertebratesin the Sacramento River USA Hydrobiologia 2002 489 117ndash129 [CrossRef]

12 Jiang XM Xiong J Qiu JW Wu JM Wang JW Xie ZC Structure of macroinvertebrate communitiesin relation to environmental variables in a subtropical Asian river system Int Rev Hydrobiol 2010 95 42ndash57[CrossRef]

Water 2016 8 27 4 of 20

considered such as watershed-related regional variables physical in-stream properties and waterquality elements

Altitude and land-use types were considered as regional variables for watershed characteristicsThe altitude at each sampling site was obtained using digital elevation data (Openmate Inc SeoulKorea) The proportion of prevalent land use types was determined for each sampling site using atopographic map (150000)

Physical in-stream properties were measured during field surveys (i) stream width for thedistance from bank to bank at a transect representative of the stream channel (ii) wetted stream widthusing a range finder (model LRM-1500M Newcon Optik Inc Toronto ON Canada) (iii) water depthof the vertical distance from the water surface to stream bottom (iv) current velocity at riffles or glidingruns using a current meter (3000-LX Swoffer Instruments Inc Tukwila WA USA) or calculated bythe Craig method [2627] (v) percent substrate composition visually estimated as fine (lt2 mm) andcoarse-sized particles (ě2 mm)

Water quality variables such as pH water temperature dissolved oxygen (DO) turbidity andelectrical conductivity (EC) were measured with a multi-probe portable meter (eg YSI 6920 YSI IncYellow Springs OH USA or Horiba U-22XD Kyoto Japan) at the center of each sampling stretch Twoliters of water samples were collected in sterilized plastic bottles at each site kept in a container withice and transported to the laboratory Laboratory measurements were conducted to determine thebiochemical oxygen demand (BOD) total nitrogen (TN) and total phosphorus (TP) following Standardmethods [28]

23 Sampling of Benthic Macroinvertebrate

A Surber sampler (30 cm ˆ 30 cm 1 mm mesh) was employed to collect benthicmacroinvertebrates Samplings were conducted at fast-flowing riffle or gliding run habitats (inthe case when suitable riffles were not available) within 100 m Quantitative samples were taken fromthree randomly selected riffles at each site pooled together in a 500 mL plastic bottle with 80 ethanoland labeled The sampling device and procedures followed the guidelines of the National AquaticEcological Monitoring Program (NAEMP) Korea [27]

After field sampling all organisms were hand-sorted from detritus and inorganic materialand stored in 70 ethanol Subsampling was permitted only for dominant taxonomic groups (egOligochaeta Ephemerellidae Chironomidae and Hydropsychidae) with large numbers of specimensavailable in each sample Each macroinvertebrate specimen was identified to the lowest possibletaxonomic level (usually genus or species) However several taxa with limited systematic information(eg Coleoptera and Diptera) were identified only to the family level All individuals were countedand converted to individualsm2

24 Data Analysis

Differences in environmental variables and macroinvertebrate assemblages were identified amongthe five major river watersheds by the KruskalndashWallis test followed by Dunnrsquos nonparametric multiplecomparison test if they are significantly different (p lt 005) Spearmanrsquos rank correlation analysiswas used to indicate the relationships between the most dominant taxa and environmental variablesA cluster analysis was conducted to classify the benthic macroinvertebrate communities using theflexible beta method (beta = acute025) with the Soslashrenson distance measure [29] Samples were classifiedinto clusters based on similarities in the community composition The multi-response permutationprocedure (MRPP [30]) which is a non-parametric method to test for differences in assemblagestructure among a priori defined groups [31] was conducted to evaluate differences among clustersDifferences in environmental variables among clusters were evaluated using the KruskalndashWallistest and Dunnrsquos nonparametric multiple comparison test The KruskalndashWallis test Dunnrsquos test andSpearman correlation analysis were performed with STATISTICA software (StatSoft Inc version 7Tulsa OK USA)

Water 2016 8 27 5 of 20

Indicator species analysis (IndVal [32]) was performed to evaluate potential indicator speciesin each cluster defined in advance The indicator value of a species is the product of its relativeabundance and frequency (ˆ 100) ranging from 0 (no indication) to 100 (perfect indication) [33]A perfect indicator of a particular group should be faithful and exclusive to that group never occurringin other groups [29] A species in a cluster that had an indicator value greater than in any othercluster was defined as good indicator species for that cluster in this study A Monte Carlo method wasperformed to test the significance of indicator values

Canonical correspondence analysis (CCA) was used to relate macroinvertebrate assemblages toenvironmental variables and to identify which environmental variables could best differentiate amongthe clusters [34] Monte-Carlo simulations were carried out to verify whether variables exerted asignificant effect (p lt 005) on macroinvertebrate distributions For the cluster analysis and CCA thosetaxa with less than 02 of total abundance were excluded to minimize the effects of rare taxa Taxaabundance data were transformed to log (x + 1) in both analyses to down-weight the effects of dominanttaxa Square-root-transformation was used for the environmental parameters expressed in percentages(eg type of land use and substrate composition) and the other variables were transformed to log(x + 1) except pH After these processes all environmental variables were rescaled in the range of0 and 1 based on the minimum-maximum range normalization [25] Spearman correlation coefficientsbetween scores and environmental variables were calculated to assist interpretation of changes incommunity profile using STATISTICA software (StatSoft Inc version 7 Tulsa OK USA) Clusteranalysis IndVal MRPP and CCA were conducted using PC-ORD software (ver 425 MjM SoftwareDesign Gleneden Beach OR USA) [34]

3 Results

31 Environmental Characteristics

Despite a large variation physicochemical factors were significantly different among watersheds(Table 1) On average the altitude percent forest and water velocity of the HRW and SRW werethe higher than the other watersheds The SRW streambeds were very heterogeneous with thehighest percentage of coarse-sized particles whereas those of the YRW contained a large amountof fine sediment High altitude fast water velocity and substrate complexity in both the HRW andSRW indicated good in-stream habitat conditions and potential to support high biodiversity andabundance of macroinvertebrates (Table 1a) The other three watersheds (NRW GRW and YRW) werecharacterized by low altitude and a high proportion of agricultural land use

Water quality parameters varied more prominently than physical variables among riverwatersheds (Table 1b) The average concentrations of DO BOD TN TP and turbidity were generallylower in the SRW than those in the other watersheds EC varied widely depending on the samplinglocation with the highest values near estuaries Nutrient-related factors were particularly high in theGRW YRW and HRW

32 Benthic Macroinvertebrate Assemblages

A total of 340 taxa belonging to 113 families in 23 orders of five phyla were identified in the fivemajor river watersheds during the survey Most of these were aquatic insects (272 species) including144 Ephemeroptera Plecoptera Trichoptera (EPT 62 mayflies 24 stoneflies and 58 caddisflies) taxaand 35 Dipteran species Taxa richness from the 720 sampling sites ranged from 0 to 49 with amean of 144 (˘ 91) with the highest diversity at HRW and the lowest in YRW (Table 2a) In contrasthomogeneous streambeds and nutrient enrichment attributed to relatively low Shannon diversity indexand high dominance index in both the NRW and YRW The proportion of EPT taxa richness rangedfrom 401 (GRW) to 548 (SRW) One-way ANOVA revealed that taxa abundance significantlydiffered among river watersheds at p lt 001 whereas there were no great differences for the relativeabundance of each taxonomic group among watersheds (Table 2b)

Water 2016 8 27 6 of 20

Table 1 Descriptive statistics of (a) regional and physical instream variables and (b) chemical variables in the five major river watersheds the Han River (HRW)Nakdong River (NRW) Geum River (GRW) Youngsan River (YRW) and Seomjin River Watershed (SRW) Top and bottom lines of each variable indicate theaverage with standard deviation (in parenthesis) and the range respectively KruskalndashWallis test (KndashW) was performed with the environmental variables to comparethe differences of each variable among river watersheds The same small letters indicate no significant difference based on Dunnrsquos multiple comparison testsAbbreviations DO dissolved oxygen BOD biochemical oxygen demand EC electrical conductivity TN total nitrogen TP total phosphorus

Variable HRW (n = 320) NRW (n = 130) GRW (n = 130) YRW (n = 76) SRW (n = 64) Total (n = 720) p (KndashW)

(a) Regional and physical instream variables

Altitude (m) 1475 (1516) d 896 (1191) bc 577 (612) ab 325 (351) a 1181 (793) cd 1061 (1262)000010ndash7210 10ndash6290 00ndash2780 00ndash2110 10ndash3350 00ndash7210

Urban317 (320) b 230 (308) ab 309 (358) b 314 (302) b 146 (124) a 284 (315)

00000ndash100 0ndash100 0ndash100 0ndash90 0ndash80 0ndash100

Agriculture 247 (275) a 425 (310) bc 466 (389) c 454 (307) c 359 (207) b 350 (317)00000ndash100 0ndash100 0ndash100 0ndash90 0ndash80 0ndash100

Forest358 (332) b 314 (278) b 179 (301) a 226 (243) a 488 (246) c 315 (313)

00000ndash100 0ndash100 0ndash100 0ndash100 0ndash95 0ndash100

Water velocity (cms) 538 (279) c 147 (140) a 381 (345) b 177 (131) a 419 (260) b 390 (304)000000ndash1400 00ndash670 00ndash1377 04ndash475 14ndash982 00ndash1400

Fine particles 311 (279) b 365 (368) bc 436 (345) c 547 (313) d 108 (229) a 350 (326)000000ndash1000 00ndash1000 00ndash1000 00ndash1000 00ndash1000 00ndash1000

Coarse particles 686 (281) c 635 (368) bc 564 (345) b 453 (313) a 892 (229) d 648 (327)000000ndash1000 00ndash1000 00ndash1000 00ndash1000 00ndash1000 00ndash1000

(b) Chemical variables

pH 81 (08) bc 80 (08) ab 83 (09) c 80 (07) ab 78 (07) a 81 (08)000365ndash101 62ndash106 70ndash111 67ndash101 67ndash96 62ndash111

DO (mgL) 978 (247) a 1081 (236) b 1086 (336) b 1006 (169) a 957 (132) a 1017 (254)0000242ndash1610 255ndash1734 274ndash1786 619ndash1540 711ndash1269 242ndash1786

BOD (mgL) 31 (37) bc 19 (13) a 37 (20) c 35 (30) bc 27 (17) b 30 (29)000003ndash375 04ndash104 08ndash91 03ndash133 03ndash123 03ndash375

EC (microScm)2998 (3376) a 13587 (60671) b 4048 (3498) a 2707 (4026) a 12846 (58234) b 5944 (31416)

0000103ndash27290 197ndash440000 861ndash27800 285ndash30820 326ndash333600 103ndash440000

TN (mgL) 315 (297) b 210 (166) a 360 (242) b 336 (359) b 232 (139) a 299 (269)0000038ndash2378 032ndash1130 029ndash1427 069ndash2771 044ndash577 029ndash2771

TP (mgL) 015 (041) bc 007 (015) ab 014 (015) bc 021 (028) c 005 (006) a 013 (030)0000000ndash559 000ndash091 001ndash101 001ndash166 000ndash032 000ndash559

Turbidity (NTU) 93 (166) b 86 (74) b 139 (223) b 78 (459) b 21 (33) a 92 (212)000000ndash1520 00ndash342 04ndash1824 00ndash4000 00ndash169 00ndash4000

Water 2016 8 27 7 of 20

Table 2 Assemblage attributes (a) and average abundance (individualsuml macute2) (b) of benthic macroinvertebrates with standard deviation (in parenthesis) in fivemajor river watersheds the Han River (HRW) Nakdong River (NRW) Geum River (GRW) Youngsan River (YRW) and Seomjin River Watershed (SRW) Relativeabundance (RA) indicated as an average of total density for each taxonomic group KruskalndashWallis test (KndashW) was performed for each taxonomic group The samesmall letters indicate no significant difference based on Dunnrsquos multiple comparison test

Biological Attributes HRW (n = 320) NRW (n = 130) GRW (n = 130) YRW (n = 76) SRW (n = 64) Total (n = 720) RA p (KndashW)

(a) Assemblage attributes

Taxa richness 157 (94) a 117 (73) b 155 (108) a 106 (63) b 151 (80) a 144 (91) - 0000EPT richness 103 (80) c 53 (55) a 76 (82) b 45 (47) a 85 (54) b 81 (75) - 0000

Taxa abundance 28675 (97919) b 8649 (10352) a 39444 (59647) b 9470 (10541) a 6120 (5482) a 22971 (71210) - 0000EPT abundance 10669 (17029) b 3032 (7265) a 15525 (24410) c 3164 (5450) a 2786 (3158) a 8674 (16472) - 0000

Dominance index 065 (021) b 070 (020) bc 071 (021) bc 073 (020) c 052 (023) a 067 (022) - 0000Shannon diversity index 233 (100) b 208 (091) b 209 (102) b 179 (094) a 263 (109) c 221 (101) - 0000

(b) Taxa abundance of higher taxonomic group

Non-Insecta

Platyhelminthes 187 (788) 287 (1967) 255 (1024) 99 (492) 172 (378) 207 (1096) 001 0447Nematomorpha 02 (09) 01 (06) 01 (05) 01 (08) 00 (00) 01 (07) 000 0082

Mollusca 107 (394) a 444 (1515) c 304 (543) b 274 (495) b 212 (309) ab 230 (765) 001 0000Annelida 6035 (68262) b 399 (908) a 5483 (29976) b 210 (614) a 681 (917) a 3827 (47310) 020 0000Crustacea 19 (122) a 429 (2143) a 412 (2439) a 1098 (5606) b 14 (70) a 277 (2306) 001 0000

Insecta

Ephemeroptera 6926 (11329) b 3166 (5946) a 5651 (10151) b 1990 (3087) a 3773 (3890) a 5215 (9360) 027 0000Odonata 39 (123) a 42 (124) a 145 (371) b 119 (292) b 07 (22) a 64 (213) 000 0000

Plecoptera 66 (216) b 56 (296) b 42 (215) ab 01 (07) a 07 (42) a 48 (213) 000 0000Hemiptera 11 (93) a 387 (2074) b 250 (1291) ab 255 (2135) ab 00 (03) a 147 (1257) 001 0000

Megaloptera 26 (104) b 12 (60) ab 16 (60) ab 05 (23) a 10 (98) ab 18 (84) 000 0000Coleoptera 153 (976) a 286 (806) a 809 (2008) c 89 (315) a 569 (949) b 326 (1193) 002 0000

Diptera 4493 (7802) b 3098 (4521) b 8062 (18533) c 3441 (7121) b 1050 (1644) a 4469 (10095) 023 0000Trichoptera 5492 (10290) b 3066 (7718) a 8453 (15644) c 1145 (2962) a 1264 (2951) a 4754 (10448) 024 0000Lepidoptera 00 (01) a - 01 (09) b 00 (06) ab - 00 (04) 000 0000Neuroptera - - - 00 (03) - 00 (01) 000 0076

Water 2016 8 27 8 of 20

Korean stream ecosystems were characterized by a few predominant colonizers and a majority ofrare taxa in macroinvertebrate assemblage composition The most abundant and widespread taxa werea worm (Limnodrilus gotoi Hatai) and midge larvae (Chironomidae spp) with their relative abundanceof approximately 50 of total density throughout the whole river watershed Other dominant specieswere mayflies (ie Baetis fuscatus (Linnaeus) Epeorus pellucidus (Brodsky) and Uracanthella punctisetae(Matsumura)) and netspinning caddisflies (Cheumatopsyche brevilineata Iwata Hydropsyche valvataMartynov and Hydropsyche kozhantschikovi Martynov) among the different stream and river systemsmost of which were dominant in somewhat nutrient-rich habitats at middle or lower streams Howeverover 50 (195 taxa) of the fauna was present with low occurring frequency (less than 2 of all sites)and 90 with low abundance (less than 02)

The environmental relationships of the dominant taxa were stronger with the physical variables(ie altitude water velocity and streambed conditions) than with the chemical variables among whichwater velocity was the most significant parameter Consequently significant positive relationshipsexisted in most dominant taxa with peak abundance at a moderate velocity of 50ndash100 cms particularlyfor E pellucidus (r = 0410 p lt 0001) and C brevilineata (r = 0435 p lt 0001) (Figure 2) Baetiella tuberculata(Kazlauskas) U punctisetae and H valvata tended to occur in their highest densities at the fast velocity(120ndash140 cms) No clear tendency was observed for Chironomidae spp

Figure 2 Distribution patterns of dominant macroinvertebrates along with water velocity Data aregiven as arithmetic means with standard deviation Spearmanrsquos rank correlation coefficients betweenwater velocity and abundance of each dominant species are included (a) Uracanthella punctisetae(b) Epeorus pellucidus (c) Baetiella tuberculata (d) Chironomini sp (e) Cheumatopsyche brevilineata(f) Hydropsyche valvata

Water 2016 8 27 9 of 20

33 Macroinvertebrate-Based Site Classification

The cluster analysis based on the similarity in the benthic macroinvertebrate composition largelyclassified the 720 sampling sites into two clusters and subsequently sub-clustered them into five groupsAs a result 126 sampling sites were included in Group 1a 199 sites in Groups 1b 106 sites in Group 2a118 sites in Group 2b and 171 sites in Group 2c (Figure 1) MRPP validated these five groups withsignificant differences (A = 0484 p lt 0001) The differences in environmental variables among theclusters are shown in Figure 3 The most important indicator taxa for each cluster are shown with theirindicator values in Table 3

Figure 3 Distribution of selected environmental variables among the five clusters of the 720 samplingsites which were identified by cluster analysis with Soslashrenson distance measure Box represents the25th and 75th percentiles and whiskers indicate the 5th and 95th percentiles with standard deviations(error bar) The mean (horizontal dotted line) and median (horizontal solid line) are shown in each boxDifferent small letters indicate significant difference based on a Dunnrsquos multiple comparison test atp lt 005

Water 2016 8 27 10 of 20

Table 3 Indicator values () for the most important species (p lt 005) in each cluster group MonteCarlo tests (999 permutations) were used to assess the significance of each species as an indicator forthe respective group (G1andashG2c) In total 50 species whose contribution to total density was higher than02 were analyzed Less important species were not shown in this table

TaxaCluster Group

pG1a G1b G2a G2b G2c

Rhyacophila nigrocephala Iwata 47 16 0 0 0 0001Epeorus nipponicus (Ueacuteno) 46 1 0 0 0 0001Glossosoma KUa 44 4 0 0 0 0001Drunella aculea (Allen) 44 1 0 0 0 0001Hydropsyche orientalis Martynov 40 7 1 1 0 0001

Uracanthella punctisetae(Matsumura)

21 48 6 6 0 0001

Hydropsyche valvata Martynov 6 46 2 9 0 0001Cheumatopsyche brevilineataIwata

15 41 5 10 0 0001

Hydropsyche kozhantschikoviMartynov

21 40 3 16 0 0001

Psychomyia sp 0 32 1 5 0 0001

Ephemera orientalis McLachlan 2 20 41 5 2 0001Ecdyonurus levis (Navaacutes) 5 28 40 1 0 0001Ecdyonurus joernensis Bengtsson 0 12 25 1 0 0001Mataeopsephus KUa 0 16 23 0 0 0001Asellus sp 0 2 11 3 6 0001

Hirudo nipponia Whitman 1 10 2 28 4 0001Chironomini sp 1 7 9 27 21 0001Limnodrilus gotoi Hatai 5 12 18 23 9 0001

Micronecta sedula Horvaacuteth 0 0 0 0 20 0001Physa acuta Draparnaud 2 3 2 12 16 0001Micronecta sp 0 0 5 0 5 0007

Total number of significantindicator species

12 21 8 3 3 -

Each cluster was clearly differentiated according to the differences of instream physicochemicalconditions and geographical location of sampling sites The cluster analysis discriminated less pollutedstreams with low EC and fast flowing water (Group 1) from moderately or severely polluted steams withhigh EC and slow water velocity (Group 2) Group 1a (G1a) congregating in the HRW consisted specificallyof mountainous upper streams although a tenth of this group was scattered over the other watershedsexcept the YRW This group consisted of oligotrophic streams with distinguishing features of the highestaltitude the lowest BOD and nutrient concentrations and the fastest water velocity Additionally thecatchment was predominantly comprised of forested area The best indicator species for this group werecharacterized as high sensitivity against organic pollution (eg Rhyacophila nigrocephala Iwata Epeorusnipponicus (Ueacuteno) Drunella aculea (Allen) and Hydropsyche orientalis Martynov) Group 1b (G1b) containedthe largest number of sampling sites and was widely distributed throughout all river watersheds butmostly encompassing the agricultural and forested catchment G1a and G1b closely resembled chemicalenvironments but steam sites belonging to G1b displayed mesotrophic condition with slightly higherBOD and nutrients than those of G1a There existed the largest number of indicator species in G1b amongwhich U punctisetae showed the highest indicator value

G2a mostly included sites located in middle reaches of large rivers and their tributariesparticularly in the NRW and SRW Although Group 2a (G2a) was similar in overall environmentalcharacteristics to G1b G2a was characterized with slightly lower altitude higher EC and a lower watervelocity when compared with G1b Sampling sites suffering from poor water quality with organicdegradation and nutrient enrichment were confined to Group 2b with the highest BOD TN and TPconcentrations These sites were influenced by the highest degree of agriculture andor urbanizationThe significant indicator species of this group were Hirudo nipponia Whitman Chironomini sp and

Water 2016 8 27 11 of 20

L gotoi indicating high trophy and saprobity [35] Water quality conditions in Group 2c (G2c) were aspoor as those of G2b with the highest EC Sites in this group were characterized with the lowest watervelocity and the largest proportion of fine particles because G2c was gathered by streams adjacent toestuaries large rivers and dammed streams The only three weak indicator species appeared in G2c

34 Environmental Variables Affecting Macroinvertebrate Distributions

A CCA was performed to understand how macroinvertebrates were distributed alongenvironmental gradients (Figure 4) Total variability explained in the species data was 159 (Table 4)The eigenvalues of the first CCA axis (0281) and the second CCA axis (0101) were significant (p lt 00199 Monte Carlo permutation test) All three CCA results were significant based on a Monte Carlopermutation test (p lt 001)

Figure 4 Ordination plots constructed by canonical correspondence analysis for all sampling sites(n = 720) The plots present the ordination of sampling sites (a) and macroinvertebrates (b) with relativecontributions of environmental variables (c) for the first two axes Only species contributing gt02to total abundance were included The summary of ordination results is presented in Table 4 and thecodes for each taxon are shown in Appendix Table A1

Water 2016 8 27 12 of 20

Table 4 Spearmanrsquos rank correlation coefficients and probabilities of environmental variables andthe CCA axes ( p lt 001 p lt 005) (a) and summary of CCA results (n = 720) (b) All axes weresignificant based on Monte Carlo permutation procedures

Variables Axis 1 Axis 2 Axis 3

(a) Correlation coefficients

Altitude 0793 0236 0013Stream order acute0105 acute0658 0099

Urban acute0218 0134 acute0317 Agriculture acute0199 acute0273 0133

Forest 0504 0055 0266 Water velocity 0662 acute0054 acute0510

Fine particles acute0744 0325 acute0076 Coarse particles 0747 acute0327 0075

pH 0011 acute0236 0007DO 0304 acute0467 acute0166

BOD acute0550 0164 acute0370 EC acute0196 acute0278 acute0116 TN acute0463 0266 acute0387 TP acute0373 0229 acute0314

(b) Summary of CCA results

Eigenvalue 0281 0101 0073 variance explained in

taxa data 98 35 25

Cumulative varianceexplained 98 133 159

p value 0010 0010 0010

Total variance 2869 - -

The five clusters were well separated in the CCA ordination plot (Figure 4a) Both the G1aand G1b groups with good physicochemical environments were positioned on the right side of theordination plot and G2b and G2c were on the opposite side However the G2a group straddledboth sides Eight environmental variables (ie BOD TN TP altitude water velocity forest fineparticles and coarse particles) had significant correlations with the first axis among which altitudewas the most significant contributor (r = 0793 p lt 001) followed by coarse particles (r = 0747p lt 001) and fine particles (r = acute0744 p lt 001) (Table 4) All physical factors except for fineparticles were in the opposite direction from the chemical variables (Figure 4c) This result suggeststhat the decline in altitude reflected deterioration in water quality accompanied by increases in organicmaterial and nutrients The heterogeneity of the macroinvertebrate habitats also decreased with thelongitudinal gradient toward downstream The second axis was negatively related with stream order(r =acute0658 p lt 001) and DO (r =acute0467 p lt 001) High positive scores with the first axis were denotedfor the rhithronic (ie pertaining to the headwaters) and intolerant species (eg Drunella aculea (Allen)E nipponicus Glossosoma sp R nigrocephala Iwata and H orientalis) whereas negative scores wereobserved for the potamic (ie pertaining to rivers) and tolerant taxa (eg Micronecta sedula HorvaacutethPhysa acuta Draparnaud Labiobaetis atrebatinus (Eaton) and Asellus hilgendorfii Bovalius) (Figure 4b)

4 Discussion

The Asian monsoon region is a global biodiversity hotspot suffering from increasinganthropogenic disturbances but aquatic biodiversity and ecosystem integrity remain poorlyexplored [3] This is the same situation in Korea but recent establishment of the National AquaticEcological Monitoring Program [36] opened a new era to assess ecosystem health and biodiversityin Korea Our work presented in this paper takes advantage of the opportunity of such anationwide scale of survey Although the five river watersheds in Korea exhibited differences in

Water 2016 8 27 13 of 20

environmental conditions and macroinvertebrate taxa abundance overall taxonomic compositionat each watershed displayed little difference (Table 2) Instead a considerable spatial variation inbenthic macroinvertebrate assemblages accounted for the combination of both ultimate (eg altitudeand the degree of land use) and proximate factors (eg flow stream bed substrate BOD EC andnutrients) This finding was in line with previous studies of benthic diatoms in Korea [25] andmacroinvertebrates in other Asian countries [1237] suggesting the importance of various multi-scalefactors in structuring macroinvertebrate assemblages [38] Our results provide basal information forthe sustainable management and conservation practices of stream ecosystems

41 Macroinvertebrate Taxonomic Composition

The macroinvertebrate assemblages in Korean stream ecosystems generally bear resemblance tothose in tropical and other temperate streams at higher taxonomic levels [3539] However temperateKorean streams were relatively rich in Ephemeroptera Diptera and Trichoptera when comparedwith tropical streams for the higher biodiversity of Gastropoda Decapoda and other insect orderssuch as Odonata and Hemiptera [3940] (Table 2) The taxonomic composition also included a largenumber of rhithronic fauna that prefer stony substrates For example Baetidae Heptageniidae andEphemerellidae mainly dominated the Ephemeroptera and Rhyacophilidae and Hydropsychidaecomposed the Trichoptera in this study

We confirmed a total of 340 macroinvertebrate taxa in this study Of the macroinvertebrate taxachironomid midge larvae and a small minnow mayfly (B fuscatus) were extensively encounteredthroughout Korean stream environments with the highest occurring frequency with 94 and 76of total sampling sites respectively Temperate Korean streams were also characterized with a fewpredominant colonizers and a majority of rare taxa in macroinvertebrate taxonomic compositionMoreover only six cosmopolitan taxa were noticeably comprised of gt60 of all macroinvertebratesamples which were L gotoi Chironomidae spp U punctisetae C brevilineata H valvata andH kozhantschikovi These dominant taxa were found to be significant indicators of mesotrophicor polytrophic streams in our study (Table 3) consistent with a result that most Korean streams andrivers were degraded in both chemical and biological status [36] On the other hand most Koreanstreams were occupied by a great number of rare macroinvertebrate species with a small distributionrange andor low abundance as was also demonstrated in other studies [4142]

42 Environmental Relationships with Macroinvertebrate Distribution

Benthic habitats are complex and a variety of environmental variables acting at multiple spatialscales regulate the composition and distribution patterns of stream macroinvertebrate assemblagesin an exclusive or synergistic fashion [3843] We revealed that the variables associated with altitudeand in-stream habitats best accounted for the largest amount of variability in our macroinvertebratedata set supporting the more important determinants of local environmental factors than broad orregional parameters [1644] The importance and role of local environmental variables have also beenhighlighted in other aquatic communities aquatic macrophytes [45] freshwater phytoplankton [46]benthic diatoms [44] intertidal macroinvertebrates [47] and fish [48] However a comprehensiveunderstanding of multispatial scales is needed because of significant correlations between macrohabitatand microhabitat characteristics depending on the relative size of the area studied [3]

In our study the variability among the macroinvertebrate-based stream groups was moreprominently explained by the altitudinal gradients together with streambed composition and watervelocity than chemical variables (Table 3) First the most widely accepted theory related to altitudinalchanges is the river continuum concept (RCC) which displays structural and functional responsesto the longitudinal gradient [49] Altitude has also been well documented in other studies as amain descriptor to determine macroinvertebrate richness as well as other environmental variablessuch as temperature hydrology food availability streambed condition and water chemistry [350]However we revealed poor relationships of altitude with water chemistry in contrast with significant

Water 2016 8 27 14 of 20

associations with physical variables and biological attributes such as taxa richness EPT richnessEPT abundance and the Shannon diversity index This may be due to the fact that over half ofthe studied streams corresponded to lowland streams below 100 m asl which were characterizedby moderate or slightly poor water quality with severe variations in BOD TN TP and Shannondiversity-based saprobity [3651] (Table 1) Harding et al [52] demonstrated that increasing humanland use intensity along a river continuum caused water quality degradation consequently leadingto changes in taxonomic composition from intolerant EPT dominated to tolerant taxa-dominatedassemblages despite a gradual increase in taxa abundance by a few dominant species

Riffle habitats are commonly characterized by shallow water depth oxygenating fast-flowingwater and stony beds and exhibit higher taxa richness and abundance than that at pools or habitatswith fine sediment as in our case [34253] Such hydraulic conditions are critical determinantsfor the distribution and species composition of benthic organisms [1654] and are the drivingforces for evolution of their morphologies and life history [11] Rheophilous (ie having an affinityfor running waters) and limnophilous taxa were clearly discriminated based on the correlationanalysis (Figure 2) and CCA (Figure 4) results For example well-known rhithronic species intwo Ephemeropteran (Ephemerellidae and Heptageniidae) and one Trichopteran (Hydropsychidae)families mostly displayed high preference to the mid- or fast current conditions which corresponds tothe intolerant scraper or filtering collector groups abundant in upper and middle stream reaches [49]Thus biological monitoring and assessment programs using rheophilic macroinvertebrates wouldbenefit from their ecological characteristics and their indication of good environmental quality(eg [42]) although seasonal fluctuations in hydraulic parameters by the Asian monsoon more criticallycause a catastrophic drift and washout of benthic organisms

Streambed composition is one of the most important factors to directly influence richness andabundance of macroinvertebrates on local scales [1216] thus close correlations would be expectedwith variables related to longitudinal changes in stream ecosystems Boulders and cobbles aretypically the major structural elements in steep gradient upper streams whereas sand and smallersediments predominate in the lower reaches [55] There have been a large number of studies onthe macroinvertebrate-substrate relationship most of which have revealed that macroinvertebratediversity and density increase with higher heterogeneity due to the available stable and diversemicrohabitats (eg [1043]) Therefore factors determining macroinvertebrate communities at localscales obviously put a priority on the streambed conditions rather than water quality or other physicalvariables We found that the mainstreams of the Nakdong River which contained about 60 fineparticles retained the lowest taxa richness (82 on average n = 18) and abundance (747 individualsm2)among five major rivers despite its good water quality condition (mean BOD 19 and TN 18 mgL)with the exception of the severely polluted Youngsan River (89 taxa richness and 73 BOD n = 13)These results indicate that homogeneous streambeds with greater fine particles support lower diversityand abundance even when streams maintain good water quality [56] Additionally organic pollutioncould transform the coarse substrate into an organic rich soft bottom altering the community structurefrom dominated by diverse and intolerant species to communities predominated by a few tolerantspecies [320] as in the case of the Youngsan River

43 Considerations to Improve Macroinvertebrate Biomonitoring Programs

Not until 2006 did Korea adopt biological water quality criteria and the concept of ecologicalintegrity in the water quality program [2536] Since then Korean government has led a biologicalsurvey of streams and rivers (ie NAEMP) every year to assess the current biological status of streamand river ecosystems and to develop a strategy for the restoration and management of disturbedsystems [25] As a part of a nationwide survey benthic macroinvertebrates are also monitored based onthe guidelines and assessment tools [27] Notwithstanding their suitability for convenient and rapidbio-assessment there remain debatable issues as to whether the methods for sampling and treating

Water 2016 8 27 15 of 20

macroinvertebrates are effective to provide a reliable and accurate indication of the macroinvertebratefauna throughout the country

The Korean national biomonitoring program presents field sampling in a cost-effective andtime-saving manner for rapid bio-assessment To satisfy this purpose benthic macroinvertebratesare optimized to be collected at riffle andor gliding run habitats using a Surber sampler with threereplicates [27] However such sampling methods probably underestimate overall biodiversity instream ecosystems considering the whole stream environment First single-habitat sampling possiblyproduces incomplete taxa lists and includes no target habitats at certain sites despite its advantagethat the influences of both water and habitat quality on macroinvertebrates are not confounded byinstream habitat variation [57] In this regard a multihabitat approach would be more profitablefor the estimation of taxonomic diversity due to its consistent application across stream typesespecially at large-scaled survey comprehensive taxa lists and effective assessment of ecologicalconditions [58] Second the Surber sampler is one of the most commonly used quantitative toolsin lotic systems and provides high-precision information on the abundance and composition ofmacroinvertebrate assemblages [2159] This method is on the other hand usually more appropriatefor riffle habitats of shallow streams presumably underestimating overall biodiversity in a regionRecent studies on the comparison between sampling devices suggested that artificial substrates(eg leaf-bags) would be used as complementary tools due to their discriminative taxonomiccomposition [60ndash62] Third a majority of biomonitoring programs widely adopt three to five replicatesfor lotic ecosystems because one way to reduce monitoring costs is to decrease the sample size [216364]The previous studies also showed that such a small number of replicates rarely influenced ecologicalhealth assessment particularly for the indices applying sensitivitytolerance taxa as the same forNAEMP [65ndash67] Nevertheless small sample sizes may influence the values of biological measuresand the representativeness for a real benthic community based on the asymptotic relationship ofthe number of taxa with both the sampling area and the collected individuals [68] Finally sievemesh size could also affect the accurate estimates of taxonomic diversity and environmental qualityassessment [67] Finer mesh sizes more accurately represent macroinvertebrate assemblages thancoarser mesh sizes whereas they need more efforts to handle specimens On the contrary coarsermesh sizes undervalue the original density and taxa richness of macroinvertebrate assemblages bypassing small individuals through the sieves and result in higher diversity [69] Considering thetradeoff between cost and effectiveness many rapid bio-assessments determine 05 mm mesh size as areasonable choice [216470] Therefore future researches are required for identifying optimal samplingeffort comprehensively considering cost-effectiveness easy applicability and well representative ofresident macroinvertebrate assemblages

5 Conclusions

Large-scale knowledge on environmental relationships of aquatic communities is crucial toconserve freshwater biodiversity and sustain ecological integrity Korean stream macroinvertebrateassemblages were determined not only by regional and physical instream variables but also bypollution-related parameters at nation-wide scale Macroinvertebrate-based site classification evidentlyprovided an environmental characterization for different types of Korean streams indicating thatbenthic macroinvertebrates are a valuable biomonitoring material The results of this study provideimportant information and a bridge for further work such as the assemblagemdashspecific responses toenvironmental disturbance Our results also contribute to establishing effective management practicesimplementing conservation measures and developing more reliable biological monitoring tools forsustainable freshwater ecosystems

Acknowledgments This study was performed under the project of ldquoNational Aquatic Ecosystem Health Surveyand Assessmentrdquo in Korea and was supported by the Ministry of Environment and the National Institute ofEnvironmental Research Korea The authors are grateful to survey members involved in the project The authorsalso thank the anonymous reviewers for their help in improving the scientific content of the manuscript

Water 2016 8 27 16 of 20

Author Contributions Yung-Chul Jun developed the concept of the study performed data analysis and wrotethe manuscript Nan-Young Kim assisted data processing and figure construction Sang-Hun Kim conductedquality assurance of the physico-chemical and biological data Young-Seuk Park and Dong-Soo Kong assistedstudy design and statistical analysis Soon-Jin Hwang supervised the research and assisted data interpretationand manuscript preparation All the authors contributed to the review of the manuscript

Conflicts of Interest The authors declare no conflict of interest

Appendix A

Table A1 Codes for macroinvertebrates contributing to more than 02 of total abundance for canonicalcorrespondence analysis in Figure 4

Code TaxonPhylum Platyhelminthes

DugSp Dugesia spPhylum Mollusca

SemLi Semisulcospira libertina (Gould)PhyAc Physa acuta Draparnaud

Phylum AnnelidaLimGo Limnodrilus gotoi HataiHirNi Hirudo nipponia Whitman

Phylum ArthropodaClass Crustacea

AseSp Asellus spGamSp Gammarus sp

Class Insecta

Order Ephemeroptera

BaeTu Baetiella tuberculata (Kazlauskas)BaeFu Baetis fuscatus (Linnaeus)BaeUr Baetis ursinus KazlauskasLabAt Labiobaetis atrebatinus (Eaton)NigBa Nigrobaetis bacillus (Kluge)EcdBa Ecdyonurus bajkovae KlugeEcdJo Ecdyonurus joernensis BengtssonEcdKi Ecdyonurus kibunensis ImanishiEcdLe Ecdyonurus levis (Navaacutes)EpeNi Epeorus nipponicus (Ueacuteno)EpeLa Epeorus latifolium (Ueacuteno)EpePe Epeorus pellucidus (Brodsky)ChoAl Choroterpes altioculus KlugeParJa Paraleptophlebia japonica (Matsumura)PotFo Potamanthus formosus EatonRhoCo Rhoenanthus coreanus (Yoon and Bae)DruAc Drunella aculea (Allen)EphOr Ephemera orientalis McLachlanSerSe Serratella setigera (Bajkova)UraPu Uracanthella punctisetae (Matsumura)CaeNi Caenis nishinoae Malzacher

Order Hemiptera

MicSe Micronecta sedula HorvaacutethMicSp Micronecta sp

Order Coleoptera

ElmSp Elmidae spEubKa Eubrianax KUaMatKa Mataeopsephus KUaPseKa Psephenoides KUa

Water 2016 8 27 17 of 20

Table A1 Cont

Code Taxon

Order Diptera

AntKa Antocha KUaCulSp Culex spChiSp Chironomidae spp (non-red type)ChiRe Chironomini spp (red-type)

Order Trichoptera

RhyNi Rhyacophila nigrocephala IwataHydKa Hydroptila KUaGloKa Glossosoma KUaCheBr Cheumatopsyche brevilineata IwataCheKa Cheumatopsyche KUaCheKb Cheumatopsyche KUbHydKo Hydropsyche kozhantschikovi MartynovHydKb Hydropsyche KUbHydOr Hydropsyche orientalis MartynovHydVa Hydropsyche valvata MartynovMacRa Macrostemum radiatum McLachlanPsySp Psychomyia sp

References

1 Dudgeon D Arthington AH Gessner MO Kawabata ZI Knowler DJ Leacutevecircque C Naiman RJPrieur-Richard AH Soto D Stiassny MLJ et al Freshwater biodiversity Importance threats status andconservation challenges Biol Rev 2006 81 163ndash182 [CrossRef] [PubMed]

2 Strayer DL Dudgeon D Freshwater biodiversity conservation Recent progress and future challengesJ N Am Benthol Soc 2010 29 344ndash358 [CrossRef]

3 Li F Chung N Bae M-J Kwon Y-S Park Y-S Relationships between stream macroinvertebrates andenvironmental variables at multiple spatial scales Freshwater Biol 2012 57 2107ndash2124 [CrossRef]

4 Dudgeon D The ecology of tropical Asian rivers and streams in relation to biodiversity conservationAnnu Rev Ecol Syst 2000 31 239ndash263 [CrossRef]

5 De Silva SS Abery NW Nguyen TTT Endemic freshwater finfish of Asia Distribution and conservationstatus Divers Distrib 2007 13 172ndash184 [CrossRef]

6 Voumlroumlsmarty CJ McIntyre PB Gessner MO Dudgeon D Prusevich A Green P Glidden S Bunn SESullivan CA Liermann CE et al Global threats to human water security and river biodiversity Nature2010 467 555ndash561 [CrossRef] [PubMed]

7 Strayer DL Challenges for freshwater invertebrate conservation J N Am Benthol Soc 2006 25 271ndash287[CrossRef]

8 Buss DF Baptista DF Silveira MP Nessimian JL Dorvilleacute LFM Influence of water chemistryand environmental degradation on macroinvertebrate assemblages in a river basin in south-east BrazilHydrobiologia 2002 481 125ndash136 [CrossRef]

9 Bott TL Brock JT Dunn CS Naiman RJ Ovink RW Petersen RC Benthic community metabolism infour temperate stream systems An inter-biome comparison and evaluation of the river continuum conceptHydrobiologia 1985 220 109ndash117 [CrossRef]

10 Merz JR Ochikubo Chan LK Effects of gravel augmentation on macroinvertebrate assemblages in aregulated California river River Res Appl 2005 21 61ndash74 [CrossRef]

11 Nelson SM Lieberman DM The influence of flow and other environmental factors on benthic invertebratesin the Sacramento River USA Hydrobiologia 2002 489 117ndash129 [CrossRef]

12 Jiang XM Xiong J Qiu JW Wu JM Wang JW Xie ZC Structure of macroinvertebrate communitiesin relation to environmental variables in a subtropical Asian river system Int Rev Hydrobiol 2010 95 42ndash57[CrossRef]

Water 2016 8 27 5 of 20

Indicator species analysis (IndVal [32]) was performed to evaluate potential indicator speciesin each cluster defined in advance The indicator value of a species is the product of its relativeabundance and frequency (ˆ 100) ranging from 0 (no indication) to 100 (perfect indication) [33]A perfect indicator of a particular group should be faithful and exclusive to that group never occurringin other groups [29] A species in a cluster that had an indicator value greater than in any othercluster was defined as good indicator species for that cluster in this study A Monte Carlo method wasperformed to test the significance of indicator values

Canonical correspondence analysis (CCA) was used to relate macroinvertebrate assemblages toenvironmental variables and to identify which environmental variables could best differentiate amongthe clusters [34] Monte-Carlo simulations were carried out to verify whether variables exerted asignificant effect (p lt 005) on macroinvertebrate distributions For the cluster analysis and CCA thosetaxa with less than 02 of total abundance were excluded to minimize the effects of rare taxa Taxaabundance data were transformed to log (x + 1) in both analyses to down-weight the effects of dominanttaxa Square-root-transformation was used for the environmental parameters expressed in percentages(eg type of land use and substrate composition) and the other variables were transformed to log(x + 1) except pH After these processes all environmental variables were rescaled in the range of0 and 1 based on the minimum-maximum range normalization [25] Spearman correlation coefficientsbetween scores and environmental variables were calculated to assist interpretation of changes incommunity profile using STATISTICA software (StatSoft Inc version 7 Tulsa OK USA) Clusteranalysis IndVal MRPP and CCA were conducted using PC-ORD software (ver 425 MjM SoftwareDesign Gleneden Beach OR USA) [34]

3 Results

31 Environmental Characteristics

Despite a large variation physicochemical factors were significantly different among watersheds(Table 1) On average the altitude percent forest and water velocity of the HRW and SRW werethe higher than the other watersheds The SRW streambeds were very heterogeneous with thehighest percentage of coarse-sized particles whereas those of the YRW contained a large amountof fine sediment High altitude fast water velocity and substrate complexity in both the HRW andSRW indicated good in-stream habitat conditions and potential to support high biodiversity andabundance of macroinvertebrates (Table 1a) The other three watersheds (NRW GRW and YRW) werecharacterized by low altitude and a high proportion of agricultural land use

Water quality parameters varied more prominently than physical variables among riverwatersheds (Table 1b) The average concentrations of DO BOD TN TP and turbidity were generallylower in the SRW than those in the other watersheds EC varied widely depending on the samplinglocation with the highest values near estuaries Nutrient-related factors were particularly high in theGRW YRW and HRW

32 Benthic Macroinvertebrate Assemblages

A total of 340 taxa belonging to 113 families in 23 orders of five phyla were identified in the fivemajor river watersheds during the survey Most of these were aquatic insects (272 species) including144 Ephemeroptera Plecoptera Trichoptera (EPT 62 mayflies 24 stoneflies and 58 caddisflies) taxaand 35 Dipteran species Taxa richness from the 720 sampling sites ranged from 0 to 49 with amean of 144 (˘ 91) with the highest diversity at HRW and the lowest in YRW (Table 2a) In contrasthomogeneous streambeds and nutrient enrichment attributed to relatively low Shannon diversity indexand high dominance index in both the NRW and YRW The proportion of EPT taxa richness rangedfrom 401 (GRW) to 548 (SRW) One-way ANOVA revealed that taxa abundance significantlydiffered among river watersheds at p lt 001 whereas there were no great differences for the relativeabundance of each taxonomic group among watersheds (Table 2b)

Water 2016 8 27 6 of 20

Table 1 Descriptive statistics of (a) regional and physical instream variables and (b) chemical variables in the five major river watersheds the Han River (HRW)Nakdong River (NRW) Geum River (GRW) Youngsan River (YRW) and Seomjin River Watershed (SRW) Top and bottom lines of each variable indicate theaverage with standard deviation (in parenthesis) and the range respectively KruskalndashWallis test (KndashW) was performed with the environmental variables to comparethe differences of each variable among river watersheds The same small letters indicate no significant difference based on Dunnrsquos multiple comparison testsAbbreviations DO dissolved oxygen BOD biochemical oxygen demand EC electrical conductivity TN total nitrogen TP total phosphorus

Variable HRW (n = 320) NRW (n = 130) GRW (n = 130) YRW (n = 76) SRW (n = 64) Total (n = 720) p (KndashW)

(a) Regional and physical instream variables

Altitude (m) 1475 (1516) d 896 (1191) bc 577 (612) ab 325 (351) a 1181 (793) cd 1061 (1262)000010ndash7210 10ndash6290 00ndash2780 00ndash2110 10ndash3350 00ndash7210

Urban317 (320) b 230 (308) ab 309 (358) b 314 (302) b 146 (124) a 284 (315)

00000ndash100 0ndash100 0ndash100 0ndash90 0ndash80 0ndash100

Agriculture 247 (275) a 425 (310) bc 466 (389) c 454 (307) c 359 (207) b 350 (317)00000ndash100 0ndash100 0ndash100 0ndash90 0ndash80 0ndash100

Forest358 (332) b 314 (278) b 179 (301) a 226 (243) a 488 (246) c 315 (313)

00000ndash100 0ndash100 0ndash100 0ndash100 0ndash95 0ndash100

Water velocity (cms) 538 (279) c 147 (140) a 381 (345) b 177 (131) a 419 (260) b 390 (304)000000ndash1400 00ndash670 00ndash1377 04ndash475 14ndash982 00ndash1400

Fine particles 311 (279) b 365 (368) bc 436 (345) c 547 (313) d 108 (229) a 350 (326)000000ndash1000 00ndash1000 00ndash1000 00ndash1000 00ndash1000 00ndash1000

Coarse particles 686 (281) c 635 (368) bc 564 (345) b 453 (313) a 892 (229) d 648 (327)000000ndash1000 00ndash1000 00ndash1000 00ndash1000 00ndash1000 00ndash1000

(b) Chemical variables

pH 81 (08) bc 80 (08) ab 83 (09) c 80 (07) ab 78 (07) a 81 (08)000365ndash101 62ndash106 70ndash111 67ndash101 67ndash96 62ndash111

DO (mgL) 978 (247) a 1081 (236) b 1086 (336) b 1006 (169) a 957 (132) a 1017 (254)0000242ndash1610 255ndash1734 274ndash1786 619ndash1540 711ndash1269 242ndash1786

BOD (mgL) 31 (37) bc 19 (13) a 37 (20) c 35 (30) bc 27 (17) b 30 (29)000003ndash375 04ndash104 08ndash91 03ndash133 03ndash123 03ndash375

EC (microScm)2998 (3376) a 13587 (60671) b 4048 (3498) a 2707 (4026) a 12846 (58234) b 5944 (31416)

0000103ndash27290 197ndash440000 861ndash27800 285ndash30820 326ndash333600 103ndash440000

TN (mgL) 315 (297) b 210 (166) a 360 (242) b 336 (359) b 232 (139) a 299 (269)0000038ndash2378 032ndash1130 029ndash1427 069ndash2771 044ndash577 029ndash2771

TP (mgL) 015 (041) bc 007 (015) ab 014 (015) bc 021 (028) c 005 (006) a 013 (030)0000000ndash559 000ndash091 001ndash101 001ndash166 000ndash032 000ndash559

Turbidity (NTU) 93 (166) b 86 (74) b 139 (223) b 78 (459) b 21 (33) a 92 (212)000000ndash1520 00ndash342 04ndash1824 00ndash4000 00ndash169 00ndash4000

Water 2016 8 27 7 of 20

Table 2 Assemblage attributes (a) and average abundance (individualsuml macute2) (b) of benthic macroinvertebrates with standard deviation (in parenthesis) in fivemajor river watersheds the Han River (HRW) Nakdong River (NRW) Geum River (GRW) Youngsan River (YRW) and Seomjin River Watershed (SRW) Relativeabundance (RA) indicated as an average of total density for each taxonomic group KruskalndashWallis test (KndashW) was performed for each taxonomic group The samesmall letters indicate no significant difference based on Dunnrsquos multiple comparison test

Biological Attributes HRW (n = 320) NRW (n = 130) GRW (n = 130) YRW (n = 76) SRW (n = 64) Total (n = 720) RA p (KndashW)

(a) Assemblage attributes

Taxa richness 157 (94) a 117 (73) b 155 (108) a 106 (63) b 151 (80) a 144 (91) - 0000EPT richness 103 (80) c 53 (55) a 76 (82) b 45 (47) a 85 (54) b 81 (75) - 0000

Taxa abundance 28675 (97919) b 8649 (10352) a 39444 (59647) b 9470 (10541) a 6120 (5482) a 22971 (71210) - 0000EPT abundance 10669 (17029) b 3032 (7265) a 15525 (24410) c 3164 (5450) a 2786 (3158) a 8674 (16472) - 0000

Dominance index 065 (021) b 070 (020) bc 071 (021) bc 073 (020) c 052 (023) a 067 (022) - 0000Shannon diversity index 233 (100) b 208 (091) b 209 (102) b 179 (094) a 263 (109) c 221 (101) - 0000

(b) Taxa abundance of higher taxonomic group

Non-Insecta

Platyhelminthes 187 (788) 287 (1967) 255 (1024) 99 (492) 172 (378) 207 (1096) 001 0447Nematomorpha 02 (09) 01 (06) 01 (05) 01 (08) 00 (00) 01 (07) 000 0082

Mollusca 107 (394) a 444 (1515) c 304 (543) b 274 (495) b 212 (309) ab 230 (765) 001 0000Annelida 6035 (68262) b 399 (908) a 5483 (29976) b 210 (614) a 681 (917) a 3827 (47310) 020 0000Crustacea 19 (122) a 429 (2143) a 412 (2439) a 1098 (5606) b 14 (70) a 277 (2306) 001 0000

Insecta

Ephemeroptera 6926 (11329) b 3166 (5946) a 5651 (10151) b 1990 (3087) a 3773 (3890) a 5215 (9360) 027 0000Odonata 39 (123) a 42 (124) a 145 (371) b 119 (292) b 07 (22) a 64 (213) 000 0000

Plecoptera 66 (216) b 56 (296) b 42 (215) ab 01 (07) a 07 (42) a 48 (213) 000 0000Hemiptera 11 (93) a 387 (2074) b 250 (1291) ab 255 (2135) ab 00 (03) a 147 (1257) 001 0000

Megaloptera 26 (104) b 12 (60) ab 16 (60) ab 05 (23) a 10 (98) ab 18 (84) 000 0000Coleoptera 153 (976) a 286 (806) a 809 (2008) c 89 (315) a 569 (949) b 326 (1193) 002 0000

Diptera 4493 (7802) b 3098 (4521) b 8062 (18533) c 3441 (7121) b 1050 (1644) a 4469 (10095) 023 0000Trichoptera 5492 (10290) b 3066 (7718) a 8453 (15644) c 1145 (2962) a 1264 (2951) a 4754 (10448) 024 0000Lepidoptera 00 (01) a - 01 (09) b 00 (06) ab - 00 (04) 000 0000Neuroptera - - - 00 (03) - 00 (01) 000 0076

Water 2016 8 27 8 of 20

Korean stream ecosystems were characterized by a few predominant colonizers and a majority ofrare taxa in macroinvertebrate assemblage composition The most abundant and widespread taxa werea worm (Limnodrilus gotoi Hatai) and midge larvae (Chironomidae spp) with their relative abundanceof approximately 50 of total density throughout the whole river watershed Other dominant specieswere mayflies (ie Baetis fuscatus (Linnaeus) Epeorus pellucidus (Brodsky) and Uracanthella punctisetae(Matsumura)) and netspinning caddisflies (Cheumatopsyche brevilineata Iwata Hydropsyche valvataMartynov and Hydropsyche kozhantschikovi Martynov) among the different stream and river systemsmost of which were dominant in somewhat nutrient-rich habitats at middle or lower streams Howeverover 50 (195 taxa) of the fauna was present with low occurring frequency (less than 2 of all sites)and 90 with low abundance (less than 02)

The environmental relationships of the dominant taxa were stronger with the physical variables(ie altitude water velocity and streambed conditions) than with the chemical variables among whichwater velocity was the most significant parameter Consequently significant positive relationshipsexisted in most dominant taxa with peak abundance at a moderate velocity of 50ndash100 cms particularlyfor E pellucidus (r = 0410 p lt 0001) and C brevilineata (r = 0435 p lt 0001) (Figure 2) Baetiella tuberculata(Kazlauskas) U punctisetae and H valvata tended to occur in their highest densities at the fast velocity(120ndash140 cms) No clear tendency was observed for Chironomidae spp

Figure 2 Distribution patterns of dominant macroinvertebrates along with water velocity Data aregiven as arithmetic means with standard deviation Spearmanrsquos rank correlation coefficients betweenwater velocity and abundance of each dominant species are included (a) Uracanthella punctisetae(b) Epeorus pellucidus (c) Baetiella tuberculata (d) Chironomini sp (e) Cheumatopsyche brevilineata(f) Hydropsyche valvata

Water 2016 8 27 9 of 20

33 Macroinvertebrate-Based Site Classification

The cluster analysis based on the similarity in the benthic macroinvertebrate composition largelyclassified the 720 sampling sites into two clusters and subsequently sub-clustered them into five groupsAs a result 126 sampling sites were included in Group 1a 199 sites in Groups 1b 106 sites in Group 2a118 sites in Group 2b and 171 sites in Group 2c (Figure 1) MRPP validated these five groups withsignificant differences (A = 0484 p lt 0001) The differences in environmental variables among theclusters are shown in Figure 3 The most important indicator taxa for each cluster are shown with theirindicator values in Table 3

Figure 3 Distribution of selected environmental variables among the five clusters of the 720 samplingsites which were identified by cluster analysis with Soslashrenson distance measure Box represents the25th and 75th percentiles and whiskers indicate the 5th and 95th percentiles with standard deviations(error bar) The mean (horizontal dotted line) and median (horizontal solid line) are shown in each boxDifferent small letters indicate significant difference based on a Dunnrsquos multiple comparison test atp lt 005

Water 2016 8 27 10 of 20

Table 3 Indicator values () for the most important species (p lt 005) in each cluster group MonteCarlo tests (999 permutations) were used to assess the significance of each species as an indicator forthe respective group (G1andashG2c) In total 50 species whose contribution to total density was higher than02 were analyzed Less important species were not shown in this table

TaxaCluster Group

pG1a G1b G2a G2b G2c

Rhyacophila nigrocephala Iwata 47 16 0 0 0 0001Epeorus nipponicus (Ueacuteno) 46 1 0 0 0 0001Glossosoma KUa 44 4 0 0 0 0001Drunella aculea (Allen) 44 1 0 0 0 0001Hydropsyche orientalis Martynov 40 7 1 1 0 0001

Uracanthella punctisetae(Matsumura)

21 48 6 6 0 0001

Hydropsyche valvata Martynov 6 46 2 9 0 0001Cheumatopsyche brevilineataIwata

15 41 5 10 0 0001

Hydropsyche kozhantschikoviMartynov

21 40 3 16 0 0001

Psychomyia sp 0 32 1 5 0 0001

Ephemera orientalis McLachlan 2 20 41 5 2 0001Ecdyonurus levis (Navaacutes) 5 28 40 1 0 0001Ecdyonurus joernensis Bengtsson 0 12 25 1 0 0001Mataeopsephus KUa 0 16 23 0 0 0001Asellus sp 0 2 11 3 6 0001

Hirudo nipponia Whitman 1 10 2 28 4 0001Chironomini sp 1 7 9 27 21 0001Limnodrilus gotoi Hatai 5 12 18 23 9 0001

Micronecta sedula Horvaacuteth 0 0 0 0 20 0001Physa acuta Draparnaud 2 3 2 12 16 0001Micronecta sp 0 0 5 0 5 0007

Total number of significantindicator species

12 21 8 3 3 -

Each cluster was clearly differentiated according to the differences of instream physicochemicalconditions and geographical location of sampling sites The cluster analysis discriminated less pollutedstreams with low EC and fast flowing water (Group 1) from moderately or severely polluted steams withhigh EC and slow water velocity (Group 2) Group 1a (G1a) congregating in the HRW consisted specificallyof mountainous upper streams although a tenth of this group was scattered over the other watershedsexcept the YRW This group consisted of oligotrophic streams with distinguishing features of the highestaltitude the lowest BOD and nutrient concentrations and the fastest water velocity Additionally thecatchment was predominantly comprised of forested area The best indicator species for this group werecharacterized as high sensitivity against organic pollution (eg Rhyacophila nigrocephala Iwata Epeorusnipponicus (Ueacuteno) Drunella aculea (Allen) and Hydropsyche orientalis Martynov) Group 1b (G1b) containedthe largest number of sampling sites and was widely distributed throughout all river watersheds butmostly encompassing the agricultural and forested catchment G1a and G1b closely resembled chemicalenvironments but steam sites belonging to G1b displayed mesotrophic condition with slightly higherBOD and nutrients than those of G1a There existed the largest number of indicator species in G1b amongwhich U punctisetae showed the highest indicator value

G2a mostly included sites located in middle reaches of large rivers and their tributariesparticularly in the NRW and SRW Although Group 2a (G2a) was similar in overall environmentalcharacteristics to G1b G2a was characterized with slightly lower altitude higher EC and a lower watervelocity when compared with G1b Sampling sites suffering from poor water quality with organicdegradation and nutrient enrichment were confined to Group 2b with the highest BOD TN and TPconcentrations These sites were influenced by the highest degree of agriculture andor urbanizationThe significant indicator species of this group were Hirudo nipponia Whitman Chironomini sp and

Water 2016 8 27 11 of 20

L gotoi indicating high trophy and saprobity [35] Water quality conditions in Group 2c (G2c) were aspoor as those of G2b with the highest EC Sites in this group were characterized with the lowest watervelocity and the largest proportion of fine particles because G2c was gathered by streams adjacent toestuaries large rivers and dammed streams The only three weak indicator species appeared in G2c

34 Environmental Variables Affecting Macroinvertebrate Distributions

A CCA was performed to understand how macroinvertebrates were distributed alongenvironmental gradients (Figure 4) Total variability explained in the species data was 159 (Table 4)The eigenvalues of the first CCA axis (0281) and the second CCA axis (0101) were significant (p lt 00199 Monte Carlo permutation test) All three CCA results were significant based on a Monte Carlopermutation test (p lt 001)

Figure 4 Ordination plots constructed by canonical correspondence analysis for all sampling sites(n = 720) The plots present the ordination of sampling sites (a) and macroinvertebrates (b) with relativecontributions of environmental variables (c) for the first two axes Only species contributing gt02to total abundance were included The summary of ordination results is presented in Table 4 and thecodes for each taxon are shown in Appendix Table A1

Water 2016 8 27 12 of 20

Table 4 Spearmanrsquos rank correlation coefficients and probabilities of environmental variables andthe CCA axes ( p lt 001 p lt 005) (a) and summary of CCA results (n = 720) (b) All axes weresignificant based on Monte Carlo permutation procedures

Variables Axis 1 Axis 2 Axis 3

(a) Correlation coefficients

Altitude 0793 0236 0013Stream order acute0105 acute0658 0099

Urban acute0218 0134 acute0317 Agriculture acute0199 acute0273 0133

Forest 0504 0055 0266 Water velocity 0662 acute0054 acute0510

Fine particles acute0744 0325 acute0076 Coarse particles 0747 acute0327 0075

pH 0011 acute0236 0007DO 0304 acute0467 acute0166

BOD acute0550 0164 acute0370 EC acute0196 acute0278 acute0116 TN acute0463 0266 acute0387 TP acute0373 0229 acute0314

(b) Summary of CCA results

Eigenvalue 0281 0101 0073 variance explained in

taxa data 98 35 25

Cumulative varianceexplained 98 133 159

p value 0010 0010 0010

Total variance 2869 - -

The five clusters were well separated in the CCA ordination plot (Figure 4a) Both the G1aand G1b groups with good physicochemical environments were positioned on the right side of theordination plot and G2b and G2c were on the opposite side However the G2a group straddledboth sides Eight environmental variables (ie BOD TN TP altitude water velocity forest fineparticles and coarse particles) had significant correlations with the first axis among which altitudewas the most significant contributor (r = 0793 p lt 001) followed by coarse particles (r = 0747p lt 001) and fine particles (r = acute0744 p lt 001) (Table 4) All physical factors except for fineparticles were in the opposite direction from the chemical variables (Figure 4c) This result suggeststhat the decline in altitude reflected deterioration in water quality accompanied by increases in organicmaterial and nutrients The heterogeneity of the macroinvertebrate habitats also decreased with thelongitudinal gradient toward downstream The second axis was negatively related with stream order(r =acute0658 p lt 001) and DO (r =acute0467 p lt 001) High positive scores with the first axis were denotedfor the rhithronic (ie pertaining to the headwaters) and intolerant species (eg Drunella aculea (Allen)E nipponicus Glossosoma sp R nigrocephala Iwata and H orientalis) whereas negative scores wereobserved for the potamic (ie pertaining to rivers) and tolerant taxa (eg Micronecta sedula HorvaacutethPhysa acuta Draparnaud Labiobaetis atrebatinus (Eaton) and Asellus hilgendorfii Bovalius) (Figure 4b)

4 Discussion

The Asian monsoon region is a global biodiversity hotspot suffering from increasinganthropogenic disturbances but aquatic biodiversity and ecosystem integrity remain poorlyexplored [3] This is the same situation in Korea but recent establishment of the National AquaticEcological Monitoring Program [36] opened a new era to assess ecosystem health and biodiversityin Korea Our work presented in this paper takes advantage of the opportunity of such anationwide scale of survey Although the five river watersheds in Korea exhibited differences in

Water 2016 8 27 13 of 20

environmental conditions and macroinvertebrate taxa abundance overall taxonomic compositionat each watershed displayed little difference (Table 2) Instead a considerable spatial variation inbenthic macroinvertebrate assemblages accounted for the combination of both ultimate (eg altitudeand the degree of land use) and proximate factors (eg flow stream bed substrate BOD EC andnutrients) This finding was in line with previous studies of benthic diatoms in Korea [25] andmacroinvertebrates in other Asian countries [1237] suggesting the importance of various multi-scalefactors in structuring macroinvertebrate assemblages [38] Our results provide basal information forthe sustainable management and conservation practices of stream ecosystems

41 Macroinvertebrate Taxonomic Composition

The macroinvertebrate assemblages in Korean stream ecosystems generally bear resemblance tothose in tropical and other temperate streams at higher taxonomic levels [3539] However temperateKorean streams were relatively rich in Ephemeroptera Diptera and Trichoptera when comparedwith tropical streams for the higher biodiversity of Gastropoda Decapoda and other insect orderssuch as Odonata and Hemiptera [3940] (Table 2) The taxonomic composition also included a largenumber of rhithronic fauna that prefer stony substrates For example Baetidae Heptageniidae andEphemerellidae mainly dominated the Ephemeroptera and Rhyacophilidae and Hydropsychidaecomposed the Trichoptera in this study

We confirmed a total of 340 macroinvertebrate taxa in this study Of the macroinvertebrate taxachironomid midge larvae and a small minnow mayfly (B fuscatus) were extensively encounteredthroughout Korean stream environments with the highest occurring frequency with 94 and 76of total sampling sites respectively Temperate Korean streams were also characterized with a fewpredominant colonizers and a majority of rare taxa in macroinvertebrate taxonomic compositionMoreover only six cosmopolitan taxa were noticeably comprised of gt60 of all macroinvertebratesamples which were L gotoi Chironomidae spp U punctisetae C brevilineata H valvata andH kozhantschikovi These dominant taxa were found to be significant indicators of mesotrophicor polytrophic streams in our study (Table 3) consistent with a result that most Korean streams andrivers were degraded in both chemical and biological status [36] On the other hand most Koreanstreams were occupied by a great number of rare macroinvertebrate species with a small distributionrange andor low abundance as was also demonstrated in other studies [4142]

42 Environmental Relationships with Macroinvertebrate Distribution

Benthic habitats are complex and a variety of environmental variables acting at multiple spatialscales regulate the composition and distribution patterns of stream macroinvertebrate assemblagesin an exclusive or synergistic fashion [3843] We revealed that the variables associated with altitudeand in-stream habitats best accounted for the largest amount of variability in our macroinvertebratedata set supporting the more important determinants of local environmental factors than broad orregional parameters [1644] The importance and role of local environmental variables have also beenhighlighted in other aquatic communities aquatic macrophytes [45] freshwater phytoplankton [46]benthic diatoms [44] intertidal macroinvertebrates [47] and fish [48] However a comprehensiveunderstanding of multispatial scales is needed because of significant correlations between macrohabitatand microhabitat characteristics depending on the relative size of the area studied [3]

In our study the variability among the macroinvertebrate-based stream groups was moreprominently explained by the altitudinal gradients together with streambed composition and watervelocity than chemical variables (Table 3) First the most widely accepted theory related to altitudinalchanges is the river continuum concept (RCC) which displays structural and functional responsesto the longitudinal gradient [49] Altitude has also been well documented in other studies as amain descriptor to determine macroinvertebrate richness as well as other environmental variablessuch as temperature hydrology food availability streambed condition and water chemistry [350]However we revealed poor relationships of altitude with water chemistry in contrast with significant

Water 2016 8 27 14 of 20

associations with physical variables and biological attributes such as taxa richness EPT richnessEPT abundance and the Shannon diversity index This may be due to the fact that over half ofthe studied streams corresponded to lowland streams below 100 m asl which were characterizedby moderate or slightly poor water quality with severe variations in BOD TN TP and Shannondiversity-based saprobity [3651] (Table 1) Harding et al [52] demonstrated that increasing humanland use intensity along a river continuum caused water quality degradation consequently leadingto changes in taxonomic composition from intolerant EPT dominated to tolerant taxa-dominatedassemblages despite a gradual increase in taxa abundance by a few dominant species

Riffle habitats are commonly characterized by shallow water depth oxygenating fast-flowingwater and stony beds and exhibit higher taxa richness and abundance than that at pools or habitatswith fine sediment as in our case [34253] Such hydraulic conditions are critical determinantsfor the distribution and species composition of benthic organisms [1654] and are the drivingforces for evolution of their morphologies and life history [11] Rheophilous (ie having an affinityfor running waters) and limnophilous taxa were clearly discriminated based on the correlationanalysis (Figure 2) and CCA (Figure 4) results For example well-known rhithronic species intwo Ephemeropteran (Ephemerellidae and Heptageniidae) and one Trichopteran (Hydropsychidae)families mostly displayed high preference to the mid- or fast current conditions which corresponds tothe intolerant scraper or filtering collector groups abundant in upper and middle stream reaches [49]Thus biological monitoring and assessment programs using rheophilic macroinvertebrates wouldbenefit from their ecological characteristics and their indication of good environmental quality(eg [42]) although seasonal fluctuations in hydraulic parameters by the Asian monsoon more criticallycause a catastrophic drift and washout of benthic organisms

Streambed composition is one of the most important factors to directly influence richness andabundance of macroinvertebrates on local scales [1216] thus close correlations would be expectedwith variables related to longitudinal changes in stream ecosystems Boulders and cobbles aretypically the major structural elements in steep gradient upper streams whereas sand and smallersediments predominate in the lower reaches [55] There have been a large number of studies onthe macroinvertebrate-substrate relationship most of which have revealed that macroinvertebratediversity and density increase with higher heterogeneity due to the available stable and diversemicrohabitats (eg [1043]) Therefore factors determining macroinvertebrate communities at localscales obviously put a priority on the streambed conditions rather than water quality or other physicalvariables We found that the mainstreams of the Nakdong River which contained about 60 fineparticles retained the lowest taxa richness (82 on average n = 18) and abundance (747 individualsm2)among five major rivers despite its good water quality condition (mean BOD 19 and TN 18 mgL)with the exception of the severely polluted Youngsan River (89 taxa richness and 73 BOD n = 13)These results indicate that homogeneous streambeds with greater fine particles support lower diversityand abundance even when streams maintain good water quality [56] Additionally organic pollutioncould transform the coarse substrate into an organic rich soft bottom altering the community structurefrom dominated by diverse and intolerant species to communities predominated by a few tolerantspecies [320] as in the case of the Youngsan River

43 Considerations to Improve Macroinvertebrate Biomonitoring Programs

Not until 2006 did Korea adopt biological water quality criteria and the concept of ecologicalintegrity in the water quality program [2536] Since then Korean government has led a biologicalsurvey of streams and rivers (ie NAEMP) every year to assess the current biological status of streamand river ecosystems and to develop a strategy for the restoration and management of disturbedsystems [25] As a part of a nationwide survey benthic macroinvertebrates are also monitored based onthe guidelines and assessment tools [27] Notwithstanding their suitability for convenient and rapidbio-assessment there remain debatable issues as to whether the methods for sampling and treating

Water 2016 8 27 15 of 20

macroinvertebrates are effective to provide a reliable and accurate indication of the macroinvertebratefauna throughout the country

The Korean national biomonitoring program presents field sampling in a cost-effective andtime-saving manner for rapid bio-assessment To satisfy this purpose benthic macroinvertebratesare optimized to be collected at riffle andor gliding run habitats using a Surber sampler with threereplicates [27] However such sampling methods probably underestimate overall biodiversity instream ecosystems considering the whole stream environment First single-habitat sampling possiblyproduces incomplete taxa lists and includes no target habitats at certain sites despite its advantagethat the influences of both water and habitat quality on macroinvertebrates are not confounded byinstream habitat variation [57] In this regard a multihabitat approach would be more profitablefor the estimation of taxonomic diversity due to its consistent application across stream typesespecially at large-scaled survey comprehensive taxa lists and effective assessment of ecologicalconditions [58] Second the Surber sampler is one of the most commonly used quantitative toolsin lotic systems and provides high-precision information on the abundance and composition ofmacroinvertebrate assemblages [2159] This method is on the other hand usually more appropriatefor riffle habitats of shallow streams presumably underestimating overall biodiversity in a regionRecent studies on the comparison between sampling devices suggested that artificial substrates(eg leaf-bags) would be used as complementary tools due to their discriminative taxonomiccomposition [60ndash62] Third a majority of biomonitoring programs widely adopt three to five replicatesfor lotic ecosystems because one way to reduce monitoring costs is to decrease the sample size [216364]The previous studies also showed that such a small number of replicates rarely influenced ecologicalhealth assessment particularly for the indices applying sensitivitytolerance taxa as the same forNAEMP [65ndash67] Nevertheless small sample sizes may influence the values of biological measuresand the representativeness for a real benthic community based on the asymptotic relationship ofthe number of taxa with both the sampling area and the collected individuals [68] Finally sievemesh size could also affect the accurate estimates of taxonomic diversity and environmental qualityassessment [67] Finer mesh sizes more accurately represent macroinvertebrate assemblages thancoarser mesh sizes whereas they need more efforts to handle specimens On the contrary coarsermesh sizes undervalue the original density and taxa richness of macroinvertebrate assemblages bypassing small individuals through the sieves and result in higher diversity [69] Considering thetradeoff between cost and effectiveness many rapid bio-assessments determine 05 mm mesh size as areasonable choice [216470] Therefore future researches are required for identifying optimal samplingeffort comprehensively considering cost-effectiveness easy applicability and well representative ofresident macroinvertebrate assemblages

5 Conclusions

Large-scale knowledge on environmental relationships of aquatic communities is crucial toconserve freshwater biodiversity and sustain ecological integrity Korean stream macroinvertebrateassemblages were determined not only by regional and physical instream variables but also bypollution-related parameters at nation-wide scale Macroinvertebrate-based site classification evidentlyprovided an environmental characterization for different types of Korean streams indicating thatbenthic macroinvertebrates are a valuable biomonitoring material The results of this study provideimportant information and a bridge for further work such as the assemblagemdashspecific responses toenvironmental disturbance Our results also contribute to establishing effective management practicesimplementing conservation measures and developing more reliable biological monitoring tools forsustainable freshwater ecosystems

Acknowledgments This study was performed under the project of ldquoNational Aquatic Ecosystem Health Surveyand Assessmentrdquo in Korea and was supported by the Ministry of Environment and the National Institute ofEnvironmental Research Korea The authors are grateful to survey members involved in the project The authorsalso thank the anonymous reviewers for their help in improving the scientific content of the manuscript

Water 2016 8 27 16 of 20

Author Contributions Yung-Chul Jun developed the concept of the study performed data analysis and wrotethe manuscript Nan-Young Kim assisted data processing and figure construction Sang-Hun Kim conductedquality assurance of the physico-chemical and biological data Young-Seuk Park and Dong-Soo Kong assistedstudy design and statistical analysis Soon-Jin Hwang supervised the research and assisted data interpretationand manuscript preparation All the authors contributed to the review of the manuscript

Conflicts of Interest The authors declare no conflict of interest

Appendix A

Table A1 Codes for macroinvertebrates contributing to more than 02 of total abundance for canonicalcorrespondence analysis in Figure 4

Code TaxonPhylum Platyhelminthes

DugSp Dugesia spPhylum Mollusca

SemLi Semisulcospira libertina (Gould)PhyAc Physa acuta Draparnaud

Phylum AnnelidaLimGo Limnodrilus gotoi HataiHirNi Hirudo nipponia Whitman

Phylum ArthropodaClass Crustacea

AseSp Asellus spGamSp Gammarus sp

Class Insecta

Order Ephemeroptera

BaeTu Baetiella tuberculata (Kazlauskas)BaeFu Baetis fuscatus (Linnaeus)BaeUr Baetis ursinus KazlauskasLabAt Labiobaetis atrebatinus (Eaton)NigBa Nigrobaetis bacillus (Kluge)EcdBa Ecdyonurus bajkovae KlugeEcdJo Ecdyonurus joernensis BengtssonEcdKi Ecdyonurus kibunensis ImanishiEcdLe Ecdyonurus levis (Navaacutes)EpeNi Epeorus nipponicus (Ueacuteno)EpeLa Epeorus latifolium (Ueacuteno)EpePe Epeorus pellucidus (Brodsky)ChoAl Choroterpes altioculus KlugeParJa Paraleptophlebia japonica (Matsumura)PotFo Potamanthus formosus EatonRhoCo Rhoenanthus coreanus (Yoon and Bae)DruAc Drunella aculea (Allen)EphOr Ephemera orientalis McLachlanSerSe Serratella setigera (Bajkova)UraPu Uracanthella punctisetae (Matsumura)CaeNi Caenis nishinoae Malzacher

Order Hemiptera

MicSe Micronecta sedula HorvaacutethMicSp Micronecta sp

Order Coleoptera

ElmSp Elmidae spEubKa Eubrianax KUaMatKa Mataeopsephus KUaPseKa Psephenoides KUa

Water 2016 8 27 17 of 20

Table A1 Cont

Code Taxon

Order Diptera

AntKa Antocha KUaCulSp Culex spChiSp Chironomidae spp (non-red type)ChiRe Chironomini spp (red-type)

Order Trichoptera

RhyNi Rhyacophila nigrocephala IwataHydKa Hydroptila KUaGloKa Glossosoma KUaCheBr Cheumatopsyche brevilineata IwataCheKa Cheumatopsyche KUaCheKb Cheumatopsyche KUbHydKo Hydropsyche kozhantschikovi MartynovHydKb Hydropsyche KUbHydOr Hydropsyche orientalis MartynovHydVa Hydropsyche valvata MartynovMacRa Macrostemum radiatum McLachlanPsySp Psychomyia sp

References

1 Dudgeon D Arthington AH Gessner MO Kawabata ZI Knowler DJ Leacutevecircque C Naiman RJPrieur-Richard AH Soto D Stiassny MLJ et al Freshwater biodiversity Importance threats status andconservation challenges Biol Rev 2006 81 163ndash182 [CrossRef] [PubMed]

2 Strayer DL Dudgeon D Freshwater biodiversity conservation Recent progress and future challengesJ N Am Benthol Soc 2010 29 344ndash358 [CrossRef]

3 Li F Chung N Bae M-J Kwon Y-S Park Y-S Relationships between stream macroinvertebrates andenvironmental variables at multiple spatial scales Freshwater Biol 2012 57 2107ndash2124 [CrossRef]

4 Dudgeon D The ecology of tropical Asian rivers and streams in relation to biodiversity conservationAnnu Rev Ecol Syst 2000 31 239ndash263 [CrossRef]

5 De Silva SS Abery NW Nguyen TTT Endemic freshwater finfish of Asia Distribution and conservationstatus Divers Distrib 2007 13 172ndash184 [CrossRef]

6 Voumlroumlsmarty CJ McIntyre PB Gessner MO Dudgeon D Prusevich A Green P Glidden S Bunn SESullivan CA Liermann CE et al Global threats to human water security and river biodiversity Nature2010 467 555ndash561 [CrossRef] [PubMed]

7 Strayer DL Challenges for freshwater invertebrate conservation J N Am Benthol Soc 2006 25 271ndash287[CrossRef]

8 Buss DF Baptista DF Silveira MP Nessimian JL Dorvilleacute LFM Influence of water chemistryand environmental degradation on macroinvertebrate assemblages in a river basin in south-east BrazilHydrobiologia 2002 481 125ndash136 [CrossRef]

9 Bott TL Brock JT Dunn CS Naiman RJ Ovink RW Petersen RC Benthic community metabolism infour temperate stream systems An inter-biome comparison and evaluation of the river continuum conceptHydrobiologia 1985 220 109ndash117 [CrossRef]

10 Merz JR Ochikubo Chan LK Effects of gravel augmentation on macroinvertebrate assemblages in aregulated California river River Res Appl 2005 21 61ndash74 [CrossRef]

11 Nelson SM Lieberman DM The influence of flow and other environmental factors on benthic invertebratesin the Sacramento River USA Hydrobiologia 2002 489 117ndash129 [CrossRef]

12 Jiang XM Xiong J Qiu JW Wu JM Wang JW Xie ZC Structure of macroinvertebrate communitiesin relation to environmental variables in a subtropical Asian river system Int Rev Hydrobiol 2010 95 42ndash57[CrossRef]

Water 2016 8 27 6 of 20

Table 1 Descriptive statistics of (a) regional and physical instream variables and (b) chemical variables in the five major river watersheds the Han River (HRW)Nakdong River (NRW) Geum River (GRW) Youngsan River (YRW) and Seomjin River Watershed (SRW) Top and bottom lines of each variable indicate theaverage with standard deviation (in parenthesis) and the range respectively KruskalndashWallis test (KndashW) was performed with the environmental variables to comparethe differences of each variable among river watersheds The same small letters indicate no significant difference based on Dunnrsquos multiple comparison testsAbbreviations DO dissolved oxygen BOD biochemical oxygen demand EC electrical conductivity TN total nitrogen TP total phosphorus

Variable HRW (n = 320) NRW (n = 130) GRW (n = 130) YRW (n = 76) SRW (n = 64) Total (n = 720) p (KndashW)

(a) Regional and physical instream variables

Altitude (m) 1475 (1516) d 896 (1191) bc 577 (612) ab 325 (351) a 1181 (793) cd 1061 (1262)000010ndash7210 10ndash6290 00ndash2780 00ndash2110 10ndash3350 00ndash7210

Urban317 (320) b 230 (308) ab 309 (358) b 314 (302) b 146 (124) a 284 (315)

00000ndash100 0ndash100 0ndash100 0ndash90 0ndash80 0ndash100

Agriculture 247 (275) a 425 (310) bc 466 (389) c 454 (307) c 359 (207) b 350 (317)00000ndash100 0ndash100 0ndash100 0ndash90 0ndash80 0ndash100

Forest358 (332) b 314 (278) b 179 (301) a 226 (243) a 488 (246) c 315 (313)

00000ndash100 0ndash100 0ndash100 0ndash100 0ndash95 0ndash100

Water velocity (cms) 538 (279) c 147 (140) a 381 (345) b 177 (131) a 419 (260) b 390 (304)000000ndash1400 00ndash670 00ndash1377 04ndash475 14ndash982 00ndash1400

Fine particles 311 (279) b 365 (368) bc 436 (345) c 547 (313) d 108 (229) a 350 (326)000000ndash1000 00ndash1000 00ndash1000 00ndash1000 00ndash1000 00ndash1000

Coarse particles 686 (281) c 635 (368) bc 564 (345) b 453 (313) a 892 (229) d 648 (327)000000ndash1000 00ndash1000 00ndash1000 00ndash1000 00ndash1000 00ndash1000

(b) Chemical variables

pH 81 (08) bc 80 (08) ab 83 (09) c 80 (07) ab 78 (07) a 81 (08)000365ndash101 62ndash106 70ndash111 67ndash101 67ndash96 62ndash111

DO (mgL) 978 (247) a 1081 (236) b 1086 (336) b 1006 (169) a 957 (132) a 1017 (254)0000242ndash1610 255ndash1734 274ndash1786 619ndash1540 711ndash1269 242ndash1786

BOD (mgL) 31 (37) bc 19 (13) a 37 (20) c 35 (30) bc 27 (17) b 30 (29)000003ndash375 04ndash104 08ndash91 03ndash133 03ndash123 03ndash375

EC (microScm)2998 (3376) a 13587 (60671) b 4048 (3498) a 2707 (4026) a 12846 (58234) b 5944 (31416)

0000103ndash27290 197ndash440000 861ndash27800 285ndash30820 326ndash333600 103ndash440000

TN (mgL) 315 (297) b 210 (166) a 360 (242) b 336 (359) b 232 (139) a 299 (269)0000038ndash2378 032ndash1130 029ndash1427 069ndash2771 044ndash577 029ndash2771

TP (mgL) 015 (041) bc 007 (015) ab 014 (015) bc 021 (028) c 005 (006) a 013 (030)0000000ndash559 000ndash091 001ndash101 001ndash166 000ndash032 000ndash559

Turbidity (NTU) 93 (166) b 86 (74) b 139 (223) b 78 (459) b 21 (33) a 92 (212)000000ndash1520 00ndash342 04ndash1824 00ndash4000 00ndash169 00ndash4000

Water 2016 8 27 7 of 20

Table 2 Assemblage attributes (a) and average abundance (individualsuml macute2) (b) of benthic macroinvertebrates with standard deviation (in parenthesis) in fivemajor river watersheds the Han River (HRW) Nakdong River (NRW) Geum River (GRW) Youngsan River (YRW) and Seomjin River Watershed (SRW) Relativeabundance (RA) indicated as an average of total density for each taxonomic group KruskalndashWallis test (KndashW) was performed for each taxonomic group The samesmall letters indicate no significant difference based on Dunnrsquos multiple comparison test

Biological Attributes HRW (n = 320) NRW (n = 130) GRW (n = 130) YRW (n = 76) SRW (n = 64) Total (n = 720) RA p (KndashW)

(a) Assemblage attributes

Taxa richness 157 (94) a 117 (73) b 155 (108) a 106 (63) b 151 (80) a 144 (91) - 0000EPT richness 103 (80) c 53 (55) a 76 (82) b 45 (47) a 85 (54) b 81 (75) - 0000

Taxa abundance 28675 (97919) b 8649 (10352) a 39444 (59647) b 9470 (10541) a 6120 (5482) a 22971 (71210) - 0000EPT abundance 10669 (17029) b 3032 (7265) a 15525 (24410) c 3164 (5450) a 2786 (3158) a 8674 (16472) - 0000

Dominance index 065 (021) b 070 (020) bc 071 (021) bc 073 (020) c 052 (023) a 067 (022) - 0000Shannon diversity index 233 (100) b 208 (091) b 209 (102) b 179 (094) a 263 (109) c 221 (101) - 0000

(b) Taxa abundance of higher taxonomic group

Non-Insecta

Platyhelminthes 187 (788) 287 (1967) 255 (1024) 99 (492) 172 (378) 207 (1096) 001 0447Nematomorpha 02 (09) 01 (06) 01 (05) 01 (08) 00 (00) 01 (07) 000 0082

Mollusca 107 (394) a 444 (1515) c 304 (543) b 274 (495) b 212 (309) ab 230 (765) 001 0000Annelida 6035 (68262) b 399 (908) a 5483 (29976) b 210 (614) a 681 (917) a 3827 (47310) 020 0000Crustacea 19 (122) a 429 (2143) a 412 (2439) a 1098 (5606) b 14 (70) a 277 (2306) 001 0000

Insecta

Ephemeroptera 6926 (11329) b 3166 (5946) a 5651 (10151) b 1990 (3087) a 3773 (3890) a 5215 (9360) 027 0000Odonata 39 (123) a 42 (124) a 145 (371) b 119 (292) b 07 (22) a 64 (213) 000 0000

Plecoptera 66 (216) b 56 (296) b 42 (215) ab 01 (07) a 07 (42) a 48 (213) 000 0000Hemiptera 11 (93) a 387 (2074) b 250 (1291) ab 255 (2135) ab 00 (03) a 147 (1257) 001 0000

Megaloptera 26 (104) b 12 (60) ab 16 (60) ab 05 (23) a 10 (98) ab 18 (84) 000 0000Coleoptera 153 (976) a 286 (806) a 809 (2008) c 89 (315) a 569 (949) b 326 (1193) 002 0000

Diptera 4493 (7802) b 3098 (4521) b 8062 (18533) c 3441 (7121) b 1050 (1644) a 4469 (10095) 023 0000Trichoptera 5492 (10290) b 3066 (7718) a 8453 (15644) c 1145 (2962) a 1264 (2951) a 4754 (10448) 024 0000Lepidoptera 00 (01) a - 01 (09) b 00 (06) ab - 00 (04) 000 0000Neuroptera - - - 00 (03) - 00 (01) 000 0076

Water 2016 8 27 8 of 20

Korean stream ecosystems were characterized by a few predominant colonizers and a majority ofrare taxa in macroinvertebrate assemblage composition The most abundant and widespread taxa werea worm (Limnodrilus gotoi Hatai) and midge larvae (Chironomidae spp) with their relative abundanceof approximately 50 of total density throughout the whole river watershed Other dominant specieswere mayflies (ie Baetis fuscatus (Linnaeus) Epeorus pellucidus (Brodsky) and Uracanthella punctisetae(Matsumura)) and netspinning caddisflies (Cheumatopsyche brevilineata Iwata Hydropsyche valvataMartynov and Hydropsyche kozhantschikovi Martynov) among the different stream and river systemsmost of which were dominant in somewhat nutrient-rich habitats at middle or lower streams Howeverover 50 (195 taxa) of the fauna was present with low occurring frequency (less than 2 of all sites)and 90 with low abundance (less than 02)

The environmental relationships of the dominant taxa were stronger with the physical variables(ie altitude water velocity and streambed conditions) than with the chemical variables among whichwater velocity was the most significant parameter Consequently significant positive relationshipsexisted in most dominant taxa with peak abundance at a moderate velocity of 50ndash100 cms particularlyfor E pellucidus (r = 0410 p lt 0001) and C brevilineata (r = 0435 p lt 0001) (Figure 2) Baetiella tuberculata(Kazlauskas) U punctisetae and H valvata tended to occur in their highest densities at the fast velocity(120ndash140 cms) No clear tendency was observed for Chironomidae spp

Figure 2 Distribution patterns of dominant macroinvertebrates along with water velocity Data aregiven as arithmetic means with standard deviation Spearmanrsquos rank correlation coefficients betweenwater velocity and abundance of each dominant species are included (a) Uracanthella punctisetae(b) Epeorus pellucidus (c) Baetiella tuberculata (d) Chironomini sp (e) Cheumatopsyche brevilineata(f) Hydropsyche valvata

Water 2016 8 27 9 of 20

33 Macroinvertebrate-Based Site Classification

The cluster analysis based on the similarity in the benthic macroinvertebrate composition largelyclassified the 720 sampling sites into two clusters and subsequently sub-clustered them into five groupsAs a result 126 sampling sites were included in Group 1a 199 sites in Groups 1b 106 sites in Group 2a118 sites in Group 2b and 171 sites in Group 2c (Figure 1) MRPP validated these five groups withsignificant differences (A = 0484 p lt 0001) The differences in environmental variables among theclusters are shown in Figure 3 The most important indicator taxa for each cluster are shown with theirindicator values in Table 3

Figure 3 Distribution of selected environmental variables among the five clusters of the 720 samplingsites which were identified by cluster analysis with Soslashrenson distance measure Box represents the25th and 75th percentiles and whiskers indicate the 5th and 95th percentiles with standard deviations(error bar) The mean (horizontal dotted line) and median (horizontal solid line) are shown in each boxDifferent small letters indicate significant difference based on a Dunnrsquos multiple comparison test atp lt 005

Water 2016 8 27 10 of 20

Table 3 Indicator values () for the most important species (p lt 005) in each cluster group MonteCarlo tests (999 permutations) were used to assess the significance of each species as an indicator forthe respective group (G1andashG2c) In total 50 species whose contribution to total density was higher than02 were analyzed Less important species were not shown in this table

TaxaCluster Group

pG1a G1b G2a G2b G2c

Rhyacophila nigrocephala Iwata 47 16 0 0 0 0001Epeorus nipponicus (Ueacuteno) 46 1 0 0 0 0001Glossosoma KUa 44 4 0 0 0 0001Drunella aculea (Allen) 44 1 0 0 0 0001Hydropsyche orientalis Martynov 40 7 1 1 0 0001

Uracanthella punctisetae(Matsumura)

21 48 6 6 0 0001

Hydropsyche valvata Martynov 6 46 2 9 0 0001Cheumatopsyche brevilineataIwata

15 41 5 10 0 0001

Hydropsyche kozhantschikoviMartynov

21 40 3 16 0 0001

Psychomyia sp 0 32 1 5 0 0001

Ephemera orientalis McLachlan 2 20 41 5 2 0001Ecdyonurus levis (Navaacutes) 5 28 40 1 0 0001Ecdyonurus joernensis Bengtsson 0 12 25 1 0 0001Mataeopsephus KUa 0 16 23 0 0 0001Asellus sp 0 2 11 3 6 0001

Hirudo nipponia Whitman 1 10 2 28 4 0001Chironomini sp 1 7 9 27 21 0001Limnodrilus gotoi Hatai 5 12 18 23 9 0001

Micronecta sedula Horvaacuteth 0 0 0 0 20 0001Physa acuta Draparnaud 2 3 2 12 16 0001Micronecta sp 0 0 5 0 5 0007

Total number of significantindicator species

12 21 8 3 3 -

Each cluster was clearly differentiated according to the differences of instream physicochemicalconditions and geographical location of sampling sites The cluster analysis discriminated less pollutedstreams with low EC and fast flowing water (Group 1) from moderately or severely polluted steams withhigh EC and slow water velocity (Group 2) Group 1a (G1a) congregating in the HRW consisted specificallyof mountainous upper streams although a tenth of this group was scattered over the other watershedsexcept the YRW This group consisted of oligotrophic streams with distinguishing features of the highestaltitude the lowest BOD and nutrient concentrations and the fastest water velocity Additionally thecatchment was predominantly comprised of forested area The best indicator species for this group werecharacterized as high sensitivity against organic pollution (eg Rhyacophila nigrocephala Iwata Epeorusnipponicus (Ueacuteno) Drunella aculea (Allen) and Hydropsyche orientalis Martynov) Group 1b (G1b) containedthe largest number of sampling sites and was widely distributed throughout all river watersheds butmostly encompassing the agricultural and forested catchment G1a and G1b closely resembled chemicalenvironments but steam sites belonging to G1b displayed mesotrophic condition with slightly higherBOD and nutrients than those of G1a There existed the largest number of indicator species in G1b amongwhich U punctisetae showed the highest indicator value

G2a mostly included sites located in middle reaches of large rivers and their tributariesparticularly in the NRW and SRW Although Group 2a (G2a) was similar in overall environmentalcharacteristics to G1b G2a was characterized with slightly lower altitude higher EC and a lower watervelocity when compared with G1b Sampling sites suffering from poor water quality with organicdegradation and nutrient enrichment were confined to Group 2b with the highest BOD TN and TPconcentrations These sites were influenced by the highest degree of agriculture andor urbanizationThe significant indicator species of this group were Hirudo nipponia Whitman Chironomini sp and

Water 2016 8 27 11 of 20

L gotoi indicating high trophy and saprobity [35] Water quality conditions in Group 2c (G2c) were aspoor as those of G2b with the highest EC Sites in this group were characterized with the lowest watervelocity and the largest proportion of fine particles because G2c was gathered by streams adjacent toestuaries large rivers and dammed streams The only three weak indicator species appeared in G2c

34 Environmental Variables Affecting Macroinvertebrate Distributions

A CCA was performed to understand how macroinvertebrates were distributed alongenvironmental gradients (Figure 4) Total variability explained in the species data was 159 (Table 4)The eigenvalues of the first CCA axis (0281) and the second CCA axis (0101) were significant (p lt 00199 Monte Carlo permutation test) All three CCA results were significant based on a Monte Carlopermutation test (p lt 001)

Figure 4 Ordination plots constructed by canonical correspondence analysis for all sampling sites(n = 720) The plots present the ordination of sampling sites (a) and macroinvertebrates (b) with relativecontributions of environmental variables (c) for the first two axes Only species contributing gt02to total abundance were included The summary of ordination results is presented in Table 4 and thecodes for each taxon are shown in Appendix Table A1

Water 2016 8 27 12 of 20

Table 4 Spearmanrsquos rank correlation coefficients and probabilities of environmental variables andthe CCA axes ( p lt 001 p lt 005) (a) and summary of CCA results (n = 720) (b) All axes weresignificant based on Monte Carlo permutation procedures

Variables Axis 1 Axis 2 Axis 3

(a) Correlation coefficients

Altitude 0793 0236 0013Stream order acute0105 acute0658 0099

Urban acute0218 0134 acute0317 Agriculture acute0199 acute0273 0133

Forest 0504 0055 0266 Water velocity 0662 acute0054 acute0510

Fine particles acute0744 0325 acute0076 Coarse particles 0747 acute0327 0075

pH 0011 acute0236 0007DO 0304 acute0467 acute0166

BOD acute0550 0164 acute0370 EC acute0196 acute0278 acute0116 TN acute0463 0266 acute0387 TP acute0373 0229 acute0314

(b) Summary of CCA results

Eigenvalue 0281 0101 0073 variance explained in

taxa data 98 35 25

Cumulative varianceexplained 98 133 159

p value 0010 0010 0010

Total variance 2869 - -

The five clusters were well separated in the CCA ordination plot (Figure 4a) Both the G1aand G1b groups with good physicochemical environments were positioned on the right side of theordination plot and G2b and G2c were on the opposite side However the G2a group straddledboth sides Eight environmental variables (ie BOD TN TP altitude water velocity forest fineparticles and coarse particles) had significant correlations with the first axis among which altitudewas the most significant contributor (r = 0793 p lt 001) followed by coarse particles (r = 0747p lt 001) and fine particles (r = acute0744 p lt 001) (Table 4) All physical factors except for fineparticles were in the opposite direction from the chemical variables (Figure 4c) This result suggeststhat the decline in altitude reflected deterioration in water quality accompanied by increases in organicmaterial and nutrients The heterogeneity of the macroinvertebrate habitats also decreased with thelongitudinal gradient toward downstream The second axis was negatively related with stream order(r =acute0658 p lt 001) and DO (r =acute0467 p lt 001) High positive scores with the first axis were denotedfor the rhithronic (ie pertaining to the headwaters) and intolerant species (eg Drunella aculea (Allen)E nipponicus Glossosoma sp R nigrocephala Iwata and H orientalis) whereas negative scores wereobserved for the potamic (ie pertaining to rivers) and tolerant taxa (eg Micronecta sedula HorvaacutethPhysa acuta Draparnaud Labiobaetis atrebatinus (Eaton) and Asellus hilgendorfii Bovalius) (Figure 4b)

4 Discussion

The Asian monsoon region is a global biodiversity hotspot suffering from increasinganthropogenic disturbances but aquatic biodiversity and ecosystem integrity remain poorlyexplored [3] This is the same situation in Korea but recent establishment of the National AquaticEcological Monitoring Program [36] opened a new era to assess ecosystem health and biodiversityin Korea Our work presented in this paper takes advantage of the opportunity of such anationwide scale of survey Although the five river watersheds in Korea exhibited differences in

Water 2016 8 27 13 of 20

environmental conditions and macroinvertebrate taxa abundance overall taxonomic compositionat each watershed displayed little difference (Table 2) Instead a considerable spatial variation inbenthic macroinvertebrate assemblages accounted for the combination of both ultimate (eg altitudeand the degree of land use) and proximate factors (eg flow stream bed substrate BOD EC andnutrients) This finding was in line with previous studies of benthic diatoms in Korea [25] andmacroinvertebrates in other Asian countries [1237] suggesting the importance of various multi-scalefactors in structuring macroinvertebrate assemblages [38] Our results provide basal information forthe sustainable management and conservation practices of stream ecosystems

41 Macroinvertebrate Taxonomic Composition

The macroinvertebrate assemblages in Korean stream ecosystems generally bear resemblance tothose in tropical and other temperate streams at higher taxonomic levels [3539] However temperateKorean streams were relatively rich in Ephemeroptera Diptera and Trichoptera when comparedwith tropical streams for the higher biodiversity of Gastropoda Decapoda and other insect orderssuch as Odonata and Hemiptera [3940] (Table 2) The taxonomic composition also included a largenumber of rhithronic fauna that prefer stony substrates For example Baetidae Heptageniidae andEphemerellidae mainly dominated the Ephemeroptera and Rhyacophilidae and Hydropsychidaecomposed the Trichoptera in this study

We confirmed a total of 340 macroinvertebrate taxa in this study Of the macroinvertebrate taxachironomid midge larvae and a small minnow mayfly (B fuscatus) were extensively encounteredthroughout Korean stream environments with the highest occurring frequency with 94 and 76of total sampling sites respectively Temperate Korean streams were also characterized with a fewpredominant colonizers and a majority of rare taxa in macroinvertebrate taxonomic compositionMoreover only six cosmopolitan taxa were noticeably comprised of gt60 of all macroinvertebratesamples which were L gotoi Chironomidae spp U punctisetae C brevilineata H valvata andH kozhantschikovi These dominant taxa were found to be significant indicators of mesotrophicor polytrophic streams in our study (Table 3) consistent with a result that most Korean streams andrivers were degraded in both chemical and biological status [36] On the other hand most Koreanstreams were occupied by a great number of rare macroinvertebrate species with a small distributionrange andor low abundance as was also demonstrated in other studies [4142]

42 Environmental Relationships with Macroinvertebrate Distribution

Benthic habitats are complex and a variety of environmental variables acting at multiple spatialscales regulate the composition and distribution patterns of stream macroinvertebrate assemblagesin an exclusive or synergistic fashion [3843] We revealed that the variables associated with altitudeand in-stream habitats best accounted for the largest amount of variability in our macroinvertebratedata set supporting the more important determinants of local environmental factors than broad orregional parameters [1644] The importance and role of local environmental variables have also beenhighlighted in other aquatic communities aquatic macrophytes [45] freshwater phytoplankton [46]benthic diatoms [44] intertidal macroinvertebrates [47] and fish [48] However a comprehensiveunderstanding of multispatial scales is needed because of significant correlations between macrohabitatand microhabitat characteristics depending on the relative size of the area studied [3]

In our study the variability among the macroinvertebrate-based stream groups was moreprominently explained by the altitudinal gradients together with streambed composition and watervelocity than chemical variables (Table 3) First the most widely accepted theory related to altitudinalchanges is the river continuum concept (RCC) which displays structural and functional responsesto the longitudinal gradient [49] Altitude has also been well documented in other studies as amain descriptor to determine macroinvertebrate richness as well as other environmental variablessuch as temperature hydrology food availability streambed condition and water chemistry [350]However we revealed poor relationships of altitude with water chemistry in contrast with significant

Water 2016 8 27 14 of 20

associations with physical variables and biological attributes such as taxa richness EPT richnessEPT abundance and the Shannon diversity index This may be due to the fact that over half ofthe studied streams corresponded to lowland streams below 100 m asl which were characterizedby moderate or slightly poor water quality with severe variations in BOD TN TP and Shannondiversity-based saprobity [3651] (Table 1) Harding et al [52] demonstrated that increasing humanland use intensity along a river continuum caused water quality degradation consequently leadingto changes in taxonomic composition from intolerant EPT dominated to tolerant taxa-dominatedassemblages despite a gradual increase in taxa abundance by a few dominant species

Riffle habitats are commonly characterized by shallow water depth oxygenating fast-flowingwater and stony beds and exhibit higher taxa richness and abundance than that at pools or habitatswith fine sediment as in our case [34253] Such hydraulic conditions are critical determinantsfor the distribution and species composition of benthic organisms [1654] and are the drivingforces for evolution of their morphologies and life history [11] Rheophilous (ie having an affinityfor running waters) and limnophilous taxa were clearly discriminated based on the correlationanalysis (Figure 2) and CCA (Figure 4) results For example well-known rhithronic species intwo Ephemeropteran (Ephemerellidae and Heptageniidae) and one Trichopteran (Hydropsychidae)families mostly displayed high preference to the mid- or fast current conditions which corresponds tothe intolerant scraper or filtering collector groups abundant in upper and middle stream reaches [49]Thus biological monitoring and assessment programs using rheophilic macroinvertebrates wouldbenefit from their ecological characteristics and their indication of good environmental quality(eg [42]) although seasonal fluctuations in hydraulic parameters by the Asian monsoon more criticallycause a catastrophic drift and washout of benthic organisms

Streambed composition is one of the most important factors to directly influence richness andabundance of macroinvertebrates on local scales [1216] thus close correlations would be expectedwith variables related to longitudinal changes in stream ecosystems Boulders and cobbles aretypically the major structural elements in steep gradient upper streams whereas sand and smallersediments predominate in the lower reaches [55] There have been a large number of studies onthe macroinvertebrate-substrate relationship most of which have revealed that macroinvertebratediversity and density increase with higher heterogeneity due to the available stable and diversemicrohabitats (eg [1043]) Therefore factors determining macroinvertebrate communities at localscales obviously put a priority on the streambed conditions rather than water quality or other physicalvariables We found that the mainstreams of the Nakdong River which contained about 60 fineparticles retained the lowest taxa richness (82 on average n = 18) and abundance (747 individualsm2)among five major rivers despite its good water quality condition (mean BOD 19 and TN 18 mgL)with the exception of the severely polluted Youngsan River (89 taxa richness and 73 BOD n = 13)These results indicate that homogeneous streambeds with greater fine particles support lower diversityand abundance even when streams maintain good water quality [56] Additionally organic pollutioncould transform the coarse substrate into an organic rich soft bottom altering the community structurefrom dominated by diverse and intolerant species to communities predominated by a few tolerantspecies [320] as in the case of the Youngsan River

43 Considerations to Improve Macroinvertebrate Biomonitoring Programs

Not until 2006 did Korea adopt biological water quality criteria and the concept of ecologicalintegrity in the water quality program [2536] Since then Korean government has led a biologicalsurvey of streams and rivers (ie NAEMP) every year to assess the current biological status of streamand river ecosystems and to develop a strategy for the restoration and management of disturbedsystems [25] As a part of a nationwide survey benthic macroinvertebrates are also monitored based onthe guidelines and assessment tools [27] Notwithstanding their suitability for convenient and rapidbio-assessment there remain debatable issues as to whether the methods for sampling and treating

Water 2016 8 27 15 of 20

macroinvertebrates are effective to provide a reliable and accurate indication of the macroinvertebratefauna throughout the country

The Korean national biomonitoring program presents field sampling in a cost-effective andtime-saving manner for rapid bio-assessment To satisfy this purpose benthic macroinvertebratesare optimized to be collected at riffle andor gliding run habitats using a Surber sampler with threereplicates [27] However such sampling methods probably underestimate overall biodiversity instream ecosystems considering the whole stream environment First single-habitat sampling possiblyproduces incomplete taxa lists and includes no target habitats at certain sites despite its advantagethat the influences of both water and habitat quality on macroinvertebrates are not confounded byinstream habitat variation [57] In this regard a multihabitat approach would be more profitablefor the estimation of taxonomic diversity due to its consistent application across stream typesespecially at large-scaled survey comprehensive taxa lists and effective assessment of ecologicalconditions [58] Second the Surber sampler is one of the most commonly used quantitative toolsin lotic systems and provides high-precision information on the abundance and composition ofmacroinvertebrate assemblages [2159] This method is on the other hand usually more appropriatefor riffle habitats of shallow streams presumably underestimating overall biodiversity in a regionRecent studies on the comparison between sampling devices suggested that artificial substrates(eg leaf-bags) would be used as complementary tools due to their discriminative taxonomiccomposition [60ndash62] Third a majority of biomonitoring programs widely adopt three to five replicatesfor lotic ecosystems because one way to reduce monitoring costs is to decrease the sample size [216364]The previous studies also showed that such a small number of replicates rarely influenced ecologicalhealth assessment particularly for the indices applying sensitivitytolerance taxa as the same forNAEMP [65ndash67] Nevertheless small sample sizes may influence the values of biological measuresand the representativeness for a real benthic community based on the asymptotic relationship ofthe number of taxa with both the sampling area and the collected individuals [68] Finally sievemesh size could also affect the accurate estimates of taxonomic diversity and environmental qualityassessment [67] Finer mesh sizes more accurately represent macroinvertebrate assemblages thancoarser mesh sizes whereas they need more efforts to handle specimens On the contrary coarsermesh sizes undervalue the original density and taxa richness of macroinvertebrate assemblages bypassing small individuals through the sieves and result in higher diversity [69] Considering thetradeoff between cost and effectiveness many rapid bio-assessments determine 05 mm mesh size as areasonable choice [216470] Therefore future researches are required for identifying optimal samplingeffort comprehensively considering cost-effectiveness easy applicability and well representative ofresident macroinvertebrate assemblages

5 Conclusions

Large-scale knowledge on environmental relationships of aquatic communities is crucial toconserve freshwater biodiversity and sustain ecological integrity Korean stream macroinvertebrateassemblages were determined not only by regional and physical instream variables but also bypollution-related parameters at nation-wide scale Macroinvertebrate-based site classification evidentlyprovided an environmental characterization for different types of Korean streams indicating thatbenthic macroinvertebrates are a valuable biomonitoring material The results of this study provideimportant information and a bridge for further work such as the assemblagemdashspecific responses toenvironmental disturbance Our results also contribute to establishing effective management practicesimplementing conservation measures and developing more reliable biological monitoring tools forsustainable freshwater ecosystems

Acknowledgments This study was performed under the project of ldquoNational Aquatic Ecosystem Health Surveyand Assessmentrdquo in Korea and was supported by the Ministry of Environment and the National Institute ofEnvironmental Research Korea The authors are grateful to survey members involved in the project The authorsalso thank the anonymous reviewers for their help in improving the scientific content of the manuscript

Water 2016 8 27 16 of 20

Author Contributions Yung-Chul Jun developed the concept of the study performed data analysis and wrotethe manuscript Nan-Young Kim assisted data processing and figure construction Sang-Hun Kim conductedquality assurance of the physico-chemical and biological data Young-Seuk Park and Dong-Soo Kong assistedstudy design and statistical analysis Soon-Jin Hwang supervised the research and assisted data interpretationand manuscript preparation All the authors contributed to the review of the manuscript

Conflicts of Interest The authors declare no conflict of interest

Appendix A

Table A1 Codes for macroinvertebrates contributing to more than 02 of total abundance for canonicalcorrespondence analysis in Figure 4

Code TaxonPhylum Platyhelminthes

DugSp Dugesia spPhylum Mollusca

SemLi Semisulcospira libertina (Gould)PhyAc Physa acuta Draparnaud

Phylum AnnelidaLimGo Limnodrilus gotoi HataiHirNi Hirudo nipponia Whitman

Phylum ArthropodaClass Crustacea

AseSp Asellus spGamSp Gammarus sp

Class Insecta

Order Ephemeroptera

BaeTu Baetiella tuberculata (Kazlauskas)BaeFu Baetis fuscatus (Linnaeus)BaeUr Baetis ursinus KazlauskasLabAt Labiobaetis atrebatinus (Eaton)NigBa Nigrobaetis bacillus (Kluge)EcdBa Ecdyonurus bajkovae KlugeEcdJo Ecdyonurus joernensis BengtssonEcdKi Ecdyonurus kibunensis ImanishiEcdLe Ecdyonurus levis (Navaacutes)EpeNi Epeorus nipponicus (Ueacuteno)EpeLa Epeorus latifolium (Ueacuteno)EpePe Epeorus pellucidus (Brodsky)ChoAl Choroterpes altioculus KlugeParJa Paraleptophlebia japonica (Matsumura)PotFo Potamanthus formosus EatonRhoCo Rhoenanthus coreanus (Yoon and Bae)DruAc Drunella aculea (Allen)EphOr Ephemera orientalis McLachlanSerSe Serratella setigera (Bajkova)UraPu Uracanthella punctisetae (Matsumura)CaeNi Caenis nishinoae Malzacher

Order Hemiptera

MicSe Micronecta sedula HorvaacutethMicSp Micronecta sp

Order Coleoptera

ElmSp Elmidae spEubKa Eubrianax KUaMatKa Mataeopsephus KUaPseKa Psephenoides KUa

Water 2016 8 27 17 of 20

Table A1 Cont

Code Taxon

Order Diptera

AntKa Antocha KUaCulSp Culex spChiSp Chironomidae spp (non-red type)ChiRe Chironomini spp (red-type)

Order Trichoptera

RhyNi Rhyacophila nigrocephala IwataHydKa Hydroptila KUaGloKa Glossosoma KUaCheBr Cheumatopsyche brevilineata IwataCheKa Cheumatopsyche KUaCheKb Cheumatopsyche KUbHydKo Hydropsyche kozhantschikovi MartynovHydKb Hydropsyche KUbHydOr Hydropsyche orientalis MartynovHydVa Hydropsyche valvata MartynovMacRa Macrostemum radiatum McLachlanPsySp Psychomyia sp

References

1 Dudgeon D Arthington AH Gessner MO Kawabata ZI Knowler DJ Leacutevecircque C Naiman RJPrieur-Richard AH Soto D Stiassny MLJ et al Freshwater biodiversity Importance threats status andconservation challenges Biol Rev 2006 81 163ndash182 [CrossRef] [PubMed]

2 Strayer DL Dudgeon D Freshwater biodiversity conservation Recent progress and future challengesJ N Am Benthol Soc 2010 29 344ndash358 [CrossRef]

3 Li F Chung N Bae M-J Kwon Y-S Park Y-S Relationships between stream macroinvertebrates andenvironmental variables at multiple spatial scales Freshwater Biol 2012 57 2107ndash2124 [CrossRef]

4 Dudgeon D The ecology of tropical Asian rivers and streams in relation to biodiversity conservationAnnu Rev Ecol Syst 2000 31 239ndash263 [CrossRef]

5 De Silva SS Abery NW Nguyen TTT Endemic freshwater finfish of Asia Distribution and conservationstatus Divers Distrib 2007 13 172ndash184 [CrossRef]

6 Voumlroumlsmarty CJ McIntyre PB Gessner MO Dudgeon D Prusevich A Green P Glidden S Bunn SESullivan CA Liermann CE et al Global threats to human water security and river biodiversity Nature2010 467 555ndash561 [CrossRef] [PubMed]

7 Strayer DL Challenges for freshwater invertebrate conservation J N Am Benthol Soc 2006 25 271ndash287[CrossRef]

8 Buss DF Baptista DF Silveira MP Nessimian JL Dorvilleacute LFM Influence of water chemistryand environmental degradation on macroinvertebrate assemblages in a river basin in south-east BrazilHydrobiologia 2002 481 125ndash136 [CrossRef]

9 Bott TL Brock JT Dunn CS Naiman RJ Ovink RW Petersen RC Benthic community metabolism infour temperate stream systems An inter-biome comparison and evaluation of the river continuum conceptHydrobiologia 1985 220 109ndash117 [CrossRef]

10 Merz JR Ochikubo Chan LK Effects of gravel augmentation on macroinvertebrate assemblages in aregulated California river River Res Appl 2005 21 61ndash74 [CrossRef]

11 Nelson SM Lieberman DM The influence of flow and other environmental factors on benthic invertebratesin the Sacramento River USA Hydrobiologia 2002 489 117ndash129 [CrossRef]

12 Jiang XM Xiong J Qiu JW Wu JM Wang JW Xie ZC Structure of macroinvertebrate communitiesin relation to environmental variables in a subtropical Asian river system Int Rev Hydrobiol 2010 95 42ndash57[CrossRef]

Water 2016 8 27 7 of 20

Table 2 Assemblage attributes (a) and average abundance (individualsuml macute2) (b) of benthic macroinvertebrates with standard deviation (in parenthesis) in fivemajor river watersheds the Han River (HRW) Nakdong River (NRW) Geum River (GRW) Youngsan River (YRW) and Seomjin River Watershed (SRW) Relativeabundance (RA) indicated as an average of total density for each taxonomic group KruskalndashWallis test (KndashW) was performed for each taxonomic group The samesmall letters indicate no significant difference based on Dunnrsquos multiple comparison test

Biological Attributes HRW (n = 320) NRW (n = 130) GRW (n = 130) YRW (n = 76) SRW (n = 64) Total (n = 720) RA p (KndashW)

(a) Assemblage attributes

Taxa richness 157 (94) a 117 (73) b 155 (108) a 106 (63) b 151 (80) a 144 (91) - 0000EPT richness 103 (80) c 53 (55) a 76 (82) b 45 (47) a 85 (54) b 81 (75) - 0000

Taxa abundance 28675 (97919) b 8649 (10352) a 39444 (59647) b 9470 (10541) a 6120 (5482) a 22971 (71210) - 0000EPT abundance 10669 (17029) b 3032 (7265) a 15525 (24410) c 3164 (5450) a 2786 (3158) a 8674 (16472) - 0000

Dominance index 065 (021) b 070 (020) bc 071 (021) bc 073 (020) c 052 (023) a 067 (022) - 0000Shannon diversity index 233 (100) b 208 (091) b 209 (102) b 179 (094) a 263 (109) c 221 (101) - 0000

(b) Taxa abundance of higher taxonomic group

Non-Insecta

Platyhelminthes 187 (788) 287 (1967) 255 (1024) 99 (492) 172 (378) 207 (1096) 001 0447Nematomorpha 02 (09) 01 (06) 01 (05) 01 (08) 00 (00) 01 (07) 000 0082

Mollusca 107 (394) a 444 (1515) c 304 (543) b 274 (495) b 212 (309) ab 230 (765) 001 0000Annelida 6035 (68262) b 399 (908) a 5483 (29976) b 210 (614) a 681 (917) a 3827 (47310) 020 0000Crustacea 19 (122) a 429 (2143) a 412 (2439) a 1098 (5606) b 14 (70) a 277 (2306) 001 0000

Insecta

Ephemeroptera 6926 (11329) b 3166 (5946) a 5651 (10151) b 1990 (3087) a 3773 (3890) a 5215 (9360) 027 0000Odonata 39 (123) a 42 (124) a 145 (371) b 119 (292) b 07 (22) a 64 (213) 000 0000

Plecoptera 66 (216) b 56 (296) b 42 (215) ab 01 (07) a 07 (42) a 48 (213) 000 0000Hemiptera 11 (93) a 387 (2074) b 250 (1291) ab 255 (2135) ab 00 (03) a 147 (1257) 001 0000

Megaloptera 26 (104) b 12 (60) ab 16 (60) ab 05 (23) a 10 (98) ab 18 (84) 000 0000Coleoptera 153 (976) a 286 (806) a 809 (2008) c 89 (315) a 569 (949) b 326 (1193) 002 0000

Diptera 4493 (7802) b 3098 (4521) b 8062 (18533) c 3441 (7121) b 1050 (1644) a 4469 (10095) 023 0000Trichoptera 5492 (10290) b 3066 (7718) a 8453 (15644) c 1145 (2962) a 1264 (2951) a 4754 (10448) 024 0000Lepidoptera 00 (01) a - 01 (09) b 00 (06) ab - 00 (04) 000 0000Neuroptera - - - 00 (03) - 00 (01) 000 0076

Water 2016 8 27 8 of 20

Korean stream ecosystems were characterized by a few predominant colonizers and a majority ofrare taxa in macroinvertebrate assemblage composition The most abundant and widespread taxa werea worm (Limnodrilus gotoi Hatai) and midge larvae (Chironomidae spp) with their relative abundanceof approximately 50 of total density throughout the whole river watershed Other dominant specieswere mayflies (ie Baetis fuscatus (Linnaeus) Epeorus pellucidus (Brodsky) and Uracanthella punctisetae(Matsumura)) and netspinning caddisflies (Cheumatopsyche brevilineata Iwata Hydropsyche valvataMartynov and Hydropsyche kozhantschikovi Martynov) among the different stream and river systemsmost of which were dominant in somewhat nutrient-rich habitats at middle or lower streams Howeverover 50 (195 taxa) of the fauna was present with low occurring frequency (less than 2 of all sites)and 90 with low abundance (less than 02)

The environmental relationships of the dominant taxa were stronger with the physical variables(ie altitude water velocity and streambed conditions) than with the chemical variables among whichwater velocity was the most significant parameter Consequently significant positive relationshipsexisted in most dominant taxa with peak abundance at a moderate velocity of 50ndash100 cms particularlyfor E pellucidus (r = 0410 p lt 0001) and C brevilineata (r = 0435 p lt 0001) (Figure 2) Baetiella tuberculata(Kazlauskas) U punctisetae and H valvata tended to occur in their highest densities at the fast velocity(120ndash140 cms) No clear tendency was observed for Chironomidae spp

Figure 2 Distribution patterns of dominant macroinvertebrates along with water velocity Data aregiven as arithmetic means with standard deviation Spearmanrsquos rank correlation coefficients betweenwater velocity and abundance of each dominant species are included (a) Uracanthella punctisetae(b) Epeorus pellucidus (c) Baetiella tuberculata (d) Chironomini sp (e) Cheumatopsyche brevilineata(f) Hydropsyche valvata

Water 2016 8 27 9 of 20

33 Macroinvertebrate-Based Site Classification

The cluster analysis based on the similarity in the benthic macroinvertebrate composition largelyclassified the 720 sampling sites into two clusters and subsequently sub-clustered them into five groupsAs a result 126 sampling sites were included in Group 1a 199 sites in Groups 1b 106 sites in Group 2a118 sites in Group 2b and 171 sites in Group 2c (Figure 1) MRPP validated these five groups withsignificant differences (A = 0484 p lt 0001) The differences in environmental variables among theclusters are shown in Figure 3 The most important indicator taxa for each cluster are shown with theirindicator values in Table 3

Figure 3 Distribution of selected environmental variables among the five clusters of the 720 samplingsites which were identified by cluster analysis with Soslashrenson distance measure Box represents the25th and 75th percentiles and whiskers indicate the 5th and 95th percentiles with standard deviations(error bar) The mean (horizontal dotted line) and median (horizontal solid line) are shown in each boxDifferent small letters indicate significant difference based on a Dunnrsquos multiple comparison test atp lt 005

Water 2016 8 27 10 of 20

Table 3 Indicator values () for the most important species (p lt 005) in each cluster group MonteCarlo tests (999 permutations) were used to assess the significance of each species as an indicator forthe respective group (G1andashG2c) In total 50 species whose contribution to total density was higher than02 were analyzed Less important species were not shown in this table

TaxaCluster Group

pG1a G1b G2a G2b G2c

Rhyacophila nigrocephala Iwata 47 16 0 0 0 0001Epeorus nipponicus (Ueacuteno) 46 1 0 0 0 0001Glossosoma KUa 44 4 0 0 0 0001Drunella aculea (Allen) 44 1 0 0 0 0001Hydropsyche orientalis Martynov 40 7 1 1 0 0001

Uracanthella punctisetae(Matsumura)

21 48 6 6 0 0001

Hydropsyche valvata Martynov 6 46 2 9 0 0001Cheumatopsyche brevilineataIwata

15 41 5 10 0 0001

Hydropsyche kozhantschikoviMartynov

21 40 3 16 0 0001

Psychomyia sp 0 32 1 5 0 0001

Ephemera orientalis McLachlan 2 20 41 5 2 0001Ecdyonurus levis (Navaacutes) 5 28 40 1 0 0001Ecdyonurus joernensis Bengtsson 0 12 25 1 0 0001Mataeopsephus KUa 0 16 23 0 0 0001Asellus sp 0 2 11 3 6 0001

Hirudo nipponia Whitman 1 10 2 28 4 0001Chironomini sp 1 7 9 27 21 0001Limnodrilus gotoi Hatai 5 12 18 23 9 0001

Micronecta sedula Horvaacuteth 0 0 0 0 20 0001Physa acuta Draparnaud 2 3 2 12 16 0001Micronecta sp 0 0 5 0 5 0007

Total number of significantindicator species

12 21 8 3 3 -

Each cluster was clearly differentiated according to the differences of instream physicochemicalconditions and geographical location of sampling sites The cluster analysis discriminated less pollutedstreams with low EC and fast flowing water (Group 1) from moderately or severely polluted steams withhigh EC and slow water velocity (Group 2) Group 1a (G1a) congregating in the HRW consisted specificallyof mountainous upper streams although a tenth of this group was scattered over the other watershedsexcept the YRW This group consisted of oligotrophic streams with distinguishing features of the highestaltitude the lowest BOD and nutrient concentrations and the fastest water velocity Additionally thecatchment was predominantly comprised of forested area The best indicator species for this group werecharacterized as high sensitivity against organic pollution (eg Rhyacophila nigrocephala Iwata Epeorusnipponicus (Ueacuteno) Drunella aculea (Allen) and Hydropsyche orientalis Martynov) Group 1b (G1b) containedthe largest number of sampling sites and was widely distributed throughout all river watersheds butmostly encompassing the agricultural and forested catchment G1a and G1b closely resembled chemicalenvironments but steam sites belonging to G1b displayed mesotrophic condition with slightly higherBOD and nutrients than those of G1a There existed the largest number of indicator species in G1b amongwhich U punctisetae showed the highest indicator value

G2a mostly included sites located in middle reaches of large rivers and their tributariesparticularly in the NRW and SRW Although Group 2a (G2a) was similar in overall environmentalcharacteristics to G1b G2a was characterized with slightly lower altitude higher EC and a lower watervelocity when compared with G1b Sampling sites suffering from poor water quality with organicdegradation and nutrient enrichment were confined to Group 2b with the highest BOD TN and TPconcentrations These sites were influenced by the highest degree of agriculture andor urbanizationThe significant indicator species of this group were Hirudo nipponia Whitman Chironomini sp and

Water 2016 8 27 11 of 20

L gotoi indicating high trophy and saprobity [35] Water quality conditions in Group 2c (G2c) were aspoor as those of G2b with the highest EC Sites in this group were characterized with the lowest watervelocity and the largest proportion of fine particles because G2c was gathered by streams adjacent toestuaries large rivers and dammed streams The only three weak indicator species appeared in G2c

34 Environmental Variables Affecting Macroinvertebrate Distributions

A CCA was performed to understand how macroinvertebrates were distributed alongenvironmental gradients (Figure 4) Total variability explained in the species data was 159 (Table 4)The eigenvalues of the first CCA axis (0281) and the second CCA axis (0101) were significant (p lt 00199 Monte Carlo permutation test) All three CCA results were significant based on a Monte Carlopermutation test (p lt 001)

Figure 4 Ordination plots constructed by canonical correspondence analysis for all sampling sites(n = 720) The plots present the ordination of sampling sites (a) and macroinvertebrates (b) with relativecontributions of environmental variables (c) for the first two axes Only species contributing gt02to total abundance were included The summary of ordination results is presented in Table 4 and thecodes for each taxon are shown in Appendix Table A1

Water 2016 8 27 12 of 20

Table 4 Spearmanrsquos rank correlation coefficients and probabilities of environmental variables andthe CCA axes ( p lt 001 p lt 005) (a) and summary of CCA results (n = 720) (b) All axes weresignificant based on Monte Carlo permutation procedures

Variables Axis 1 Axis 2 Axis 3

(a) Correlation coefficients

Altitude 0793 0236 0013Stream order acute0105 acute0658 0099

Urban acute0218 0134 acute0317 Agriculture acute0199 acute0273 0133

Forest 0504 0055 0266 Water velocity 0662 acute0054 acute0510

Fine particles acute0744 0325 acute0076 Coarse particles 0747 acute0327 0075

pH 0011 acute0236 0007DO 0304 acute0467 acute0166

BOD acute0550 0164 acute0370 EC acute0196 acute0278 acute0116 TN acute0463 0266 acute0387 TP acute0373 0229 acute0314

(b) Summary of CCA results

Eigenvalue 0281 0101 0073 variance explained in

taxa data 98 35 25

Cumulative varianceexplained 98 133 159

p value 0010 0010 0010

Total variance 2869 - -

The five clusters were well separated in the CCA ordination plot (Figure 4a) Both the G1aand G1b groups with good physicochemical environments were positioned on the right side of theordination plot and G2b and G2c were on the opposite side However the G2a group straddledboth sides Eight environmental variables (ie BOD TN TP altitude water velocity forest fineparticles and coarse particles) had significant correlations with the first axis among which altitudewas the most significant contributor (r = 0793 p lt 001) followed by coarse particles (r = 0747p lt 001) and fine particles (r = acute0744 p lt 001) (Table 4) All physical factors except for fineparticles were in the opposite direction from the chemical variables (Figure 4c) This result suggeststhat the decline in altitude reflected deterioration in water quality accompanied by increases in organicmaterial and nutrients The heterogeneity of the macroinvertebrate habitats also decreased with thelongitudinal gradient toward downstream The second axis was negatively related with stream order(r =acute0658 p lt 001) and DO (r =acute0467 p lt 001) High positive scores with the first axis were denotedfor the rhithronic (ie pertaining to the headwaters) and intolerant species (eg Drunella aculea (Allen)E nipponicus Glossosoma sp R nigrocephala Iwata and H orientalis) whereas negative scores wereobserved for the potamic (ie pertaining to rivers) and tolerant taxa (eg Micronecta sedula HorvaacutethPhysa acuta Draparnaud Labiobaetis atrebatinus (Eaton) and Asellus hilgendorfii Bovalius) (Figure 4b)

4 Discussion

The Asian monsoon region is a global biodiversity hotspot suffering from increasinganthropogenic disturbances but aquatic biodiversity and ecosystem integrity remain poorlyexplored [3] This is the same situation in Korea but recent establishment of the National AquaticEcological Monitoring Program [36] opened a new era to assess ecosystem health and biodiversityin Korea Our work presented in this paper takes advantage of the opportunity of such anationwide scale of survey Although the five river watersheds in Korea exhibited differences in

Water 2016 8 27 13 of 20

environmental conditions and macroinvertebrate taxa abundance overall taxonomic compositionat each watershed displayed little difference (Table 2) Instead a considerable spatial variation inbenthic macroinvertebrate assemblages accounted for the combination of both ultimate (eg altitudeand the degree of land use) and proximate factors (eg flow stream bed substrate BOD EC andnutrients) This finding was in line with previous studies of benthic diatoms in Korea [25] andmacroinvertebrates in other Asian countries [1237] suggesting the importance of various multi-scalefactors in structuring macroinvertebrate assemblages [38] Our results provide basal information forthe sustainable management and conservation practices of stream ecosystems

41 Macroinvertebrate Taxonomic Composition

The macroinvertebrate assemblages in Korean stream ecosystems generally bear resemblance tothose in tropical and other temperate streams at higher taxonomic levels [3539] However temperateKorean streams were relatively rich in Ephemeroptera Diptera and Trichoptera when comparedwith tropical streams for the higher biodiversity of Gastropoda Decapoda and other insect orderssuch as Odonata and Hemiptera [3940] (Table 2) The taxonomic composition also included a largenumber of rhithronic fauna that prefer stony substrates For example Baetidae Heptageniidae andEphemerellidae mainly dominated the Ephemeroptera and Rhyacophilidae and Hydropsychidaecomposed the Trichoptera in this study

We confirmed a total of 340 macroinvertebrate taxa in this study Of the macroinvertebrate taxachironomid midge larvae and a small minnow mayfly (B fuscatus) were extensively encounteredthroughout Korean stream environments with the highest occurring frequency with 94 and 76of total sampling sites respectively Temperate Korean streams were also characterized with a fewpredominant colonizers and a majority of rare taxa in macroinvertebrate taxonomic compositionMoreover only six cosmopolitan taxa were noticeably comprised of gt60 of all macroinvertebratesamples which were L gotoi Chironomidae spp U punctisetae C brevilineata H valvata andH kozhantschikovi These dominant taxa were found to be significant indicators of mesotrophicor polytrophic streams in our study (Table 3) consistent with a result that most Korean streams andrivers were degraded in both chemical and biological status [36] On the other hand most Koreanstreams were occupied by a great number of rare macroinvertebrate species with a small distributionrange andor low abundance as was also demonstrated in other studies [4142]

42 Environmental Relationships with Macroinvertebrate Distribution

Benthic habitats are complex and a variety of environmental variables acting at multiple spatialscales regulate the composition and distribution patterns of stream macroinvertebrate assemblagesin an exclusive or synergistic fashion [3843] We revealed that the variables associated with altitudeand in-stream habitats best accounted for the largest amount of variability in our macroinvertebratedata set supporting the more important determinants of local environmental factors than broad orregional parameters [1644] The importance and role of local environmental variables have also beenhighlighted in other aquatic communities aquatic macrophytes [45] freshwater phytoplankton [46]benthic diatoms [44] intertidal macroinvertebrates [47] and fish [48] However a comprehensiveunderstanding of multispatial scales is needed because of significant correlations between macrohabitatand microhabitat characteristics depending on the relative size of the area studied [3]

In our study the variability among the macroinvertebrate-based stream groups was moreprominently explained by the altitudinal gradients together with streambed composition and watervelocity than chemical variables (Table 3) First the most widely accepted theory related to altitudinalchanges is the river continuum concept (RCC) which displays structural and functional responsesto the longitudinal gradient [49] Altitude has also been well documented in other studies as amain descriptor to determine macroinvertebrate richness as well as other environmental variablessuch as temperature hydrology food availability streambed condition and water chemistry [350]However we revealed poor relationships of altitude with water chemistry in contrast with significant

Water 2016 8 27 14 of 20

associations with physical variables and biological attributes such as taxa richness EPT richnessEPT abundance and the Shannon diversity index This may be due to the fact that over half ofthe studied streams corresponded to lowland streams below 100 m asl which were characterizedby moderate or slightly poor water quality with severe variations in BOD TN TP and Shannondiversity-based saprobity [3651] (Table 1) Harding et al [52] demonstrated that increasing humanland use intensity along a river continuum caused water quality degradation consequently leadingto changes in taxonomic composition from intolerant EPT dominated to tolerant taxa-dominatedassemblages despite a gradual increase in taxa abundance by a few dominant species

Riffle habitats are commonly characterized by shallow water depth oxygenating fast-flowingwater and stony beds and exhibit higher taxa richness and abundance than that at pools or habitatswith fine sediment as in our case [34253] Such hydraulic conditions are critical determinantsfor the distribution and species composition of benthic organisms [1654] and are the drivingforces for evolution of their morphologies and life history [11] Rheophilous (ie having an affinityfor running waters) and limnophilous taxa were clearly discriminated based on the correlationanalysis (Figure 2) and CCA (Figure 4) results For example well-known rhithronic species intwo Ephemeropteran (Ephemerellidae and Heptageniidae) and one Trichopteran (Hydropsychidae)families mostly displayed high preference to the mid- or fast current conditions which corresponds tothe intolerant scraper or filtering collector groups abundant in upper and middle stream reaches [49]Thus biological monitoring and assessment programs using rheophilic macroinvertebrates wouldbenefit from their ecological characteristics and their indication of good environmental quality(eg [42]) although seasonal fluctuations in hydraulic parameters by the Asian monsoon more criticallycause a catastrophic drift and washout of benthic organisms

Streambed composition is one of the most important factors to directly influence richness andabundance of macroinvertebrates on local scales [1216] thus close correlations would be expectedwith variables related to longitudinal changes in stream ecosystems Boulders and cobbles aretypically the major structural elements in steep gradient upper streams whereas sand and smallersediments predominate in the lower reaches [55] There have been a large number of studies onthe macroinvertebrate-substrate relationship most of which have revealed that macroinvertebratediversity and density increase with higher heterogeneity due to the available stable and diversemicrohabitats (eg [1043]) Therefore factors determining macroinvertebrate communities at localscales obviously put a priority on the streambed conditions rather than water quality or other physicalvariables We found that the mainstreams of the Nakdong River which contained about 60 fineparticles retained the lowest taxa richness (82 on average n = 18) and abundance (747 individualsm2)among five major rivers despite its good water quality condition (mean BOD 19 and TN 18 mgL)with the exception of the severely polluted Youngsan River (89 taxa richness and 73 BOD n = 13)These results indicate that homogeneous streambeds with greater fine particles support lower diversityand abundance even when streams maintain good water quality [56] Additionally organic pollutioncould transform the coarse substrate into an organic rich soft bottom altering the community structurefrom dominated by diverse and intolerant species to communities predominated by a few tolerantspecies [320] as in the case of the Youngsan River

43 Considerations to Improve Macroinvertebrate Biomonitoring Programs

Not until 2006 did Korea adopt biological water quality criteria and the concept of ecologicalintegrity in the water quality program [2536] Since then Korean government has led a biologicalsurvey of streams and rivers (ie NAEMP) every year to assess the current biological status of streamand river ecosystems and to develop a strategy for the restoration and management of disturbedsystems [25] As a part of a nationwide survey benthic macroinvertebrates are also monitored based onthe guidelines and assessment tools [27] Notwithstanding their suitability for convenient and rapidbio-assessment there remain debatable issues as to whether the methods for sampling and treating

Water 2016 8 27 15 of 20

macroinvertebrates are effective to provide a reliable and accurate indication of the macroinvertebratefauna throughout the country

The Korean national biomonitoring program presents field sampling in a cost-effective andtime-saving manner for rapid bio-assessment To satisfy this purpose benthic macroinvertebratesare optimized to be collected at riffle andor gliding run habitats using a Surber sampler with threereplicates [27] However such sampling methods probably underestimate overall biodiversity instream ecosystems considering the whole stream environment First single-habitat sampling possiblyproduces incomplete taxa lists and includes no target habitats at certain sites despite its advantagethat the influences of both water and habitat quality on macroinvertebrates are not confounded byinstream habitat variation [57] In this regard a multihabitat approach would be more profitablefor the estimation of taxonomic diversity due to its consistent application across stream typesespecially at large-scaled survey comprehensive taxa lists and effective assessment of ecologicalconditions [58] Second the Surber sampler is one of the most commonly used quantitative toolsin lotic systems and provides high-precision information on the abundance and composition ofmacroinvertebrate assemblages [2159] This method is on the other hand usually more appropriatefor riffle habitats of shallow streams presumably underestimating overall biodiversity in a regionRecent studies on the comparison between sampling devices suggested that artificial substrates(eg leaf-bags) would be used as complementary tools due to their discriminative taxonomiccomposition [60ndash62] Third a majority of biomonitoring programs widely adopt three to five replicatesfor lotic ecosystems because one way to reduce monitoring costs is to decrease the sample size [216364]The previous studies also showed that such a small number of replicates rarely influenced ecologicalhealth assessment particularly for the indices applying sensitivitytolerance taxa as the same forNAEMP [65ndash67] Nevertheless small sample sizes may influence the values of biological measuresand the representativeness for a real benthic community based on the asymptotic relationship ofthe number of taxa with both the sampling area and the collected individuals [68] Finally sievemesh size could also affect the accurate estimates of taxonomic diversity and environmental qualityassessment [67] Finer mesh sizes more accurately represent macroinvertebrate assemblages thancoarser mesh sizes whereas they need more efforts to handle specimens On the contrary coarsermesh sizes undervalue the original density and taxa richness of macroinvertebrate assemblages bypassing small individuals through the sieves and result in higher diversity [69] Considering thetradeoff between cost and effectiveness many rapid bio-assessments determine 05 mm mesh size as areasonable choice [216470] Therefore future researches are required for identifying optimal samplingeffort comprehensively considering cost-effectiveness easy applicability and well representative ofresident macroinvertebrate assemblages

5 Conclusions

Large-scale knowledge on environmental relationships of aquatic communities is crucial toconserve freshwater biodiversity and sustain ecological integrity Korean stream macroinvertebrateassemblages were determined not only by regional and physical instream variables but also bypollution-related parameters at nation-wide scale Macroinvertebrate-based site classification evidentlyprovided an environmental characterization for different types of Korean streams indicating thatbenthic macroinvertebrates are a valuable biomonitoring material The results of this study provideimportant information and a bridge for further work such as the assemblagemdashspecific responses toenvironmental disturbance Our results also contribute to establishing effective management practicesimplementing conservation measures and developing more reliable biological monitoring tools forsustainable freshwater ecosystems

Acknowledgments This study was performed under the project of ldquoNational Aquatic Ecosystem Health Surveyand Assessmentrdquo in Korea and was supported by the Ministry of Environment and the National Institute ofEnvironmental Research Korea The authors are grateful to survey members involved in the project The authorsalso thank the anonymous reviewers for their help in improving the scientific content of the manuscript

Water 2016 8 27 16 of 20

Author Contributions Yung-Chul Jun developed the concept of the study performed data analysis and wrotethe manuscript Nan-Young Kim assisted data processing and figure construction Sang-Hun Kim conductedquality assurance of the physico-chemical and biological data Young-Seuk Park and Dong-Soo Kong assistedstudy design and statistical analysis Soon-Jin Hwang supervised the research and assisted data interpretationand manuscript preparation All the authors contributed to the review of the manuscript

Conflicts of Interest The authors declare no conflict of interest

Appendix A

Table A1 Codes for macroinvertebrates contributing to more than 02 of total abundance for canonicalcorrespondence analysis in Figure 4

Code TaxonPhylum Platyhelminthes

DugSp Dugesia spPhylum Mollusca

SemLi Semisulcospira libertina (Gould)PhyAc Physa acuta Draparnaud

Phylum AnnelidaLimGo Limnodrilus gotoi HataiHirNi Hirudo nipponia Whitman

Phylum ArthropodaClass Crustacea

AseSp Asellus spGamSp Gammarus sp

Class Insecta

Order Ephemeroptera

BaeTu Baetiella tuberculata (Kazlauskas)BaeFu Baetis fuscatus (Linnaeus)BaeUr Baetis ursinus KazlauskasLabAt Labiobaetis atrebatinus (Eaton)NigBa Nigrobaetis bacillus (Kluge)EcdBa Ecdyonurus bajkovae KlugeEcdJo Ecdyonurus joernensis BengtssonEcdKi Ecdyonurus kibunensis ImanishiEcdLe Ecdyonurus levis (Navaacutes)EpeNi Epeorus nipponicus (Ueacuteno)EpeLa Epeorus latifolium (Ueacuteno)EpePe Epeorus pellucidus (Brodsky)ChoAl Choroterpes altioculus KlugeParJa Paraleptophlebia japonica (Matsumura)PotFo Potamanthus formosus EatonRhoCo Rhoenanthus coreanus (Yoon and Bae)DruAc Drunella aculea (Allen)EphOr Ephemera orientalis McLachlanSerSe Serratella setigera (Bajkova)UraPu Uracanthella punctisetae (Matsumura)CaeNi Caenis nishinoae Malzacher

Order Hemiptera

MicSe Micronecta sedula HorvaacutethMicSp Micronecta sp

Order Coleoptera

ElmSp Elmidae spEubKa Eubrianax KUaMatKa Mataeopsephus KUaPseKa Psephenoides KUa

Water 2016 8 27 17 of 20

Table A1 Cont

Code Taxon

Order Diptera

AntKa Antocha KUaCulSp Culex spChiSp Chironomidae spp (non-red type)ChiRe Chironomini spp (red-type)

Order Trichoptera

RhyNi Rhyacophila nigrocephala IwataHydKa Hydroptila KUaGloKa Glossosoma KUaCheBr Cheumatopsyche brevilineata IwataCheKa Cheumatopsyche KUaCheKb Cheumatopsyche KUbHydKo Hydropsyche kozhantschikovi MartynovHydKb Hydropsyche KUbHydOr Hydropsyche orientalis MartynovHydVa Hydropsyche valvata MartynovMacRa Macrostemum radiatum McLachlanPsySp Psychomyia sp

References

1 Dudgeon D Arthington AH Gessner MO Kawabata ZI Knowler DJ Leacutevecircque C Naiman RJPrieur-Richard AH Soto D Stiassny MLJ et al Freshwater biodiversity Importance threats status andconservation challenges Biol Rev 2006 81 163ndash182 [CrossRef] [PubMed]

2 Strayer DL Dudgeon D Freshwater biodiversity conservation Recent progress and future challengesJ N Am Benthol Soc 2010 29 344ndash358 [CrossRef]

3 Li F Chung N Bae M-J Kwon Y-S Park Y-S Relationships between stream macroinvertebrates andenvironmental variables at multiple spatial scales Freshwater Biol 2012 57 2107ndash2124 [CrossRef]

4 Dudgeon D The ecology of tropical Asian rivers and streams in relation to biodiversity conservationAnnu Rev Ecol Syst 2000 31 239ndash263 [CrossRef]

5 De Silva SS Abery NW Nguyen TTT Endemic freshwater finfish of Asia Distribution and conservationstatus Divers Distrib 2007 13 172ndash184 [CrossRef]

6 Voumlroumlsmarty CJ McIntyre PB Gessner MO Dudgeon D Prusevich A Green P Glidden S Bunn SESullivan CA Liermann CE et al Global threats to human water security and river biodiversity Nature2010 467 555ndash561 [CrossRef] [PubMed]

7 Strayer DL Challenges for freshwater invertebrate conservation J N Am Benthol Soc 2006 25 271ndash287[CrossRef]

8 Buss DF Baptista DF Silveira MP Nessimian JL Dorvilleacute LFM Influence of water chemistryand environmental degradation on macroinvertebrate assemblages in a river basin in south-east BrazilHydrobiologia 2002 481 125ndash136 [CrossRef]

9 Bott TL Brock JT Dunn CS Naiman RJ Ovink RW Petersen RC Benthic community metabolism infour temperate stream systems An inter-biome comparison and evaluation of the river continuum conceptHydrobiologia 1985 220 109ndash117 [CrossRef]

10 Merz JR Ochikubo Chan LK Effects of gravel augmentation on macroinvertebrate assemblages in aregulated California river River Res Appl 2005 21 61ndash74 [CrossRef]

11 Nelson SM Lieberman DM The influence of flow and other environmental factors on benthic invertebratesin the Sacramento River USA Hydrobiologia 2002 489 117ndash129 [CrossRef]

12 Jiang XM Xiong J Qiu JW Wu JM Wang JW Xie ZC Structure of macroinvertebrate communitiesin relation to environmental variables in a subtropical Asian river system Int Rev Hydrobiol 2010 95 42ndash57[CrossRef]

Water 2016 8 27 8 of 20

Korean stream ecosystems were characterized by a few predominant colonizers and a majority ofrare taxa in macroinvertebrate assemblage composition The most abundant and widespread taxa werea worm (Limnodrilus gotoi Hatai) and midge larvae (Chironomidae spp) with their relative abundanceof approximately 50 of total density throughout the whole river watershed Other dominant specieswere mayflies (ie Baetis fuscatus (Linnaeus) Epeorus pellucidus (Brodsky) and Uracanthella punctisetae(Matsumura)) and netspinning caddisflies (Cheumatopsyche brevilineata Iwata Hydropsyche valvataMartynov and Hydropsyche kozhantschikovi Martynov) among the different stream and river systemsmost of which were dominant in somewhat nutrient-rich habitats at middle or lower streams Howeverover 50 (195 taxa) of the fauna was present with low occurring frequency (less than 2 of all sites)and 90 with low abundance (less than 02)

The environmental relationships of the dominant taxa were stronger with the physical variables(ie altitude water velocity and streambed conditions) than with the chemical variables among whichwater velocity was the most significant parameter Consequently significant positive relationshipsexisted in most dominant taxa with peak abundance at a moderate velocity of 50ndash100 cms particularlyfor E pellucidus (r = 0410 p lt 0001) and C brevilineata (r = 0435 p lt 0001) (Figure 2) Baetiella tuberculata(Kazlauskas) U punctisetae and H valvata tended to occur in their highest densities at the fast velocity(120ndash140 cms) No clear tendency was observed for Chironomidae spp

Figure 2 Distribution patterns of dominant macroinvertebrates along with water velocity Data aregiven as arithmetic means with standard deviation Spearmanrsquos rank correlation coefficients betweenwater velocity and abundance of each dominant species are included (a) Uracanthella punctisetae(b) Epeorus pellucidus (c) Baetiella tuberculata (d) Chironomini sp (e) Cheumatopsyche brevilineata(f) Hydropsyche valvata

Water 2016 8 27 9 of 20

33 Macroinvertebrate-Based Site Classification

The cluster analysis based on the similarity in the benthic macroinvertebrate composition largelyclassified the 720 sampling sites into two clusters and subsequently sub-clustered them into five groupsAs a result 126 sampling sites were included in Group 1a 199 sites in Groups 1b 106 sites in Group 2a118 sites in Group 2b and 171 sites in Group 2c (Figure 1) MRPP validated these five groups withsignificant differences (A = 0484 p lt 0001) The differences in environmental variables among theclusters are shown in Figure 3 The most important indicator taxa for each cluster are shown with theirindicator values in Table 3

Figure 3 Distribution of selected environmental variables among the five clusters of the 720 samplingsites which were identified by cluster analysis with Soslashrenson distance measure Box represents the25th and 75th percentiles and whiskers indicate the 5th and 95th percentiles with standard deviations(error bar) The mean (horizontal dotted line) and median (horizontal solid line) are shown in each boxDifferent small letters indicate significant difference based on a Dunnrsquos multiple comparison test atp lt 005

Water 2016 8 27 10 of 20

Table 3 Indicator values () for the most important species (p lt 005) in each cluster group MonteCarlo tests (999 permutations) were used to assess the significance of each species as an indicator forthe respective group (G1andashG2c) In total 50 species whose contribution to total density was higher than02 were analyzed Less important species were not shown in this table

TaxaCluster Group

pG1a G1b G2a G2b G2c

Rhyacophila nigrocephala Iwata 47 16 0 0 0 0001Epeorus nipponicus (Ueacuteno) 46 1 0 0 0 0001Glossosoma KUa 44 4 0 0 0 0001Drunella aculea (Allen) 44 1 0 0 0 0001Hydropsyche orientalis Martynov 40 7 1 1 0 0001

Uracanthella punctisetae(Matsumura)

21 48 6 6 0 0001

Hydropsyche valvata Martynov 6 46 2 9 0 0001Cheumatopsyche brevilineataIwata

15 41 5 10 0 0001

Hydropsyche kozhantschikoviMartynov

21 40 3 16 0 0001

Psychomyia sp 0 32 1 5 0 0001

Ephemera orientalis McLachlan 2 20 41 5 2 0001Ecdyonurus levis (Navaacutes) 5 28 40 1 0 0001Ecdyonurus joernensis Bengtsson 0 12 25 1 0 0001Mataeopsephus KUa 0 16 23 0 0 0001Asellus sp 0 2 11 3 6 0001

Hirudo nipponia Whitman 1 10 2 28 4 0001Chironomini sp 1 7 9 27 21 0001Limnodrilus gotoi Hatai 5 12 18 23 9 0001

Micronecta sedula Horvaacuteth 0 0 0 0 20 0001Physa acuta Draparnaud 2 3 2 12 16 0001Micronecta sp 0 0 5 0 5 0007

Total number of significantindicator species

12 21 8 3 3 -

Each cluster was clearly differentiated according to the differences of instream physicochemicalconditions and geographical location of sampling sites The cluster analysis discriminated less pollutedstreams with low EC and fast flowing water (Group 1) from moderately or severely polluted steams withhigh EC and slow water velocity (Group 2) Group 1a (G1a) congregating in the HRW consisted specificallyof mountainous upper streams although a tenth of this group was scattered over the other watershedsexcept the YRW This group consisted of oligotrophic streams with distinguishing features of the highestaltitude the lowest BOD and nutrient concentrations and the fastest water velocity Additionally thecatchment was predominantly comprised of forested area The best indicator species for this group werecharacterized as high sensitivity against organic pollution (eg Rhyacophila nigrocephala Iwata Epeorusnipponicus (Ueacuteno) Drunella aculea (Allen) and Hydropsyche orientalis Martynov) Group 1b (G1b) containedthe largest number of sampling sites and was widely distributed throughout all river watersheds butmostly encompassing the agricultural and forested catchment G1a and G1b closely resembled chemicalenvironments but steam sites belonging to G1b displayed mesotrophic condition with slightly higherBOD and nutrients than those of G1a There existed the largest number of indicator species in G1b amongwhich U punctisetae showed the highest indicator value

G2a mostly included sites located in middle reaches of large rivers and their tributariesparticularly in the NRW and SRW Although Group 2a (G2a) was similar in overall environmentalcharacteristics to G1b G2a was characterized with slightly lower altitude higher EC and a lower watervelocity when compared with G1b Sampling sites suffering from poor water quality with organicdegradation and nutrient enrichment were confined to Group 2b with the highest BOD TN and TPconcentrations These sites were influenced by the highest degree of agriculture andor urbanizationThe significant indicator species of this group were Hirudo nipponia Whitman Chironomini sp and

Water 2016 8 27 11 of 20

L gotoi indicating high trophy and saprobity [35] Water quality conditions in Group 2c (G2c) were aspoor as those of G2b with the highest EC Sites in this group were characterized with the lowest watervelocity and the largest proportion of fine particles because G2c was gathered by streams adjacent toestuaries large rivers and dammed streams The only three weak indicator species appeared in G2c

34 Environmental Variables Affecting Macroinvertebrate Distributions

A CCA was performed to understand how macroinvertebrates were distributed alongenvironmental gradients (Figure 4) Total variability explained in the species data was 159 (Table 4)The eigenvalues of the first CCA axis (0281) and the second CCA axis (0101) were significant (p lt 00199 Monte Carlo permutation test) All three CCA results were significant based on a Monte Carlopermutation test (p lt 001)

Figure 4 Ordination plots constructed by canonical correspondence analysis for all sampling sites(n = 720) The plots present the ordination of sampling sites (a) and macroinvertebrates (b) with relativecontributions of environmental variables (c) for the first two axes Only species contributing gt02to total abundance were included The summary of ordination results is presented in Table 4 and thecodes for each taxon are shown in Appendix Table A1

Water 2016 8 27 12 of 20

Table 4 Spearmanrsquos rank correlation coefficients and probabilities of environmental variables andthe CCA axes ( p lt 001 p lt 005) (a) and summary of CCA results (n = 720) (b) All axes weresignificant based on Monte Carlo permutation procedures

Variables Axis 1 Axis 2 Axis 3

(a) Correlation coefficients

Altitude 0793 0236 0013Stream order acute0105 acute0658 0099

Urban acute0218 0134 acute0317 Agriculture acute0199 acute0273 0133

Forest 0504 0055 0266 Water velocity 0662 acute0054 acute0510

Fine particles acute0744 0325 acute0076 Coarse particles 0747 acute0327 0075

pH 0011 acute0236 0007DO 0304 acute0467 acute0166

BOD acute0550 0164 acute0370 EC acute0196 acute0278 acute0116 TN acute0463 0266 acute0387 TP acute0373 0229 acute0314

(b) Summary of CCA results

Eigenvalue 0281 0101 0073 variance explained in

taxa data 98 35 25

Cumulative varianceexplained 98 133 159

p value 0010 0010 0010

Total variance 2869 - -

The five clusters were well separated in the CCA ordination plot (Figure 4a) Both the G1aand G1b groups with good physicochemical environments were positioned on the right side of theordination plot and G2b and G2c were on the opposite side However the G2a group straddledboth sides Eight environmental variables (ie BOD TN TP altitude water velocity forest fineparticles and coarse particles) had significant correlations with the first axis among which altitudewas the most significant contributor (r = 0793 p lt 001) followed by coarse particles (r = 0747p lt 001) and fine particles (r = acute0744 p lt 001) (Table 4) All physical factors except for fineparticles were in the opposite direction from the chemical variables (Figure 4c) This result suggeststhat the decline in altitude reflected deterioration in water quality accompanied by increases in organicmaterial and nutrients The heterogeneity of the macroinvertebrate habitats also decreased with thelongitudinal gradient toward downstream The second axis was negatively related with stream order(r =acute0658 p lt 001) and DO (r =acute0467 p lt 001) High positive scores with the first axis were denotedfor the rhithronic (ie pertaining to the headwaters) and intolerant species (eg Drunella aculea (Allen)E nipponicus Glossosoma sp R nigrocephala Iwata and H orientalis) whereas negative scores wereobserved for the potamic (ie pertaining to rivers) and tolerant taxa (eg Micronecta sedula HorvaacutethPhysa acuta Draparnaud Labiobaetis atrebatinus (Eaton) and Asellus hilgendorfii Bovalius) (Figure 4b)

4 Discussion

The Asian monsoon region is a global biodiversity hotspot suffering from increasinganthropogenic disturbances but aquatic biodiversity and ecosystem integrity remain poorlyexplored [3] This is the same situation in Korea but recent establishment of the National AquaticEcological Monitoring Program [36] opened a new era to assess ecosystem health and biodiversityin Korea Our work presented in this paper takes advantage of the opportunity of such anationwide scale of survey Although the five river watersheds in Korea exhibited differences in

Water 2016 8 27 13 of 20

environmental conditions and macroinvertebrate taxa abundance overall taxonomic compositionat each watershed displayed little difference (Table 2) Instead a considerable spatial variation inbenthic macroinvertebrate assemblages accounted for the combination of both ultimate (eg altitudeand the degree of land use) and proximate factors (eg flow stream bed substrate BOD EC andnutrients) This finding was in line with previous studies of benthic diatoms in Korea [25] andmacroinvertebrates in other Asian countries [1237] suggesting the importance of various multi-scalefactors in structuring macroinvertebrate assemblages [38] Our results provide basal information forthe sustainable management and conservation practices of stream ecosystems

41 Macroinvertebrate Taxonomic Composition

The macroinvertebrate assemblages in Korean stream ecosystems generally bear resemblance tothose in tropical and other temperate streams at higher taxonomic levels [3539] However temperateKorean streams were relatively rich in Ephemeroptera Diptera and Trichoptera when comparedwith tropical streams for the higher biodiversity of Gastropoda Decapoda and other insect orderssuch as Odonata and Hemiptera [3940] (Table 2) The taxonomic composition also included a largenumber of rhithronic fauna that prefer stony substrates For example Baetidae Heptageniidae andEphemerellidae mainly dominated the Ephemeroptera and Rhyacophilidae and Hydropsychidaecomposed the Trichoptera in this study

We confirmed a total of 340 macroinvertebrate taxa in this study Of the macroinvertebrate taxachironomid midge larvae and a small minnow mayfly (B fuscatus) were extensively encounteredthroughout Korean stream environments with the highest occurring frequency with 94 and 76of total sampling sites respectively Temperate Korean streams were also characterized with a fewpredominant colonizers and a majority of rare taxa in macroinvertebrate taxonomic compositionMoreover only six cosmopolitan taxa were noticeably comprised of gt60 of all macroinvertebratesamples which were L gotoi Chironomidae spp U punctisetae C brevilineata H valvata andH kozhantschikovi These dominant taxa were found to be significant indicators of mesotrophicor polytrophic streams in our study (Table 3) consistent with a result that most Korean streams andrivers were degraded in both chemical and biological status [36] On the other hand most Koreanstreams were occupied by a great number of rare macroinvertebrate species with a small distributionrange andor low abundance as was also demonstrated in other studies [4142]

42 Environmental Relationships with Macroinvertebrate Distribution

Benthic habitats are complex and a variety of environmental variables acting at multiple spatialscales regulate the composition and distribution patterns of stream macroinvertebrate assemblagesin an exclusive or synergistic fashion [3843] We revealed that the variables associated with altitudeand in-stream habitats best accounted for the largest amount of variability in our macroinvertebratedata set supporting the more important determinants of local environmental factors than broad orregional parameters [1644] The importance and role of local environmental variables have also beenhighlighted in other aquatic communities aquatic macrophytes [45] freshwater phytoplankton [46]benthic diatoms [44] intertidal macroinvertebrates [47] and fish [48] However a comprehensiveunderstanding of multispatial scales is needed because of significant correlations between macrohabitatand microhabitat characteristics depending on the relative size of the area studied [3]

In our study the variability among the macroinvertebrate-based stream groups was moreprominently explained by the altitudinal gradients together with streambed composition and watervelocity than chemical variables (Table 3) First the most widely accepted theory related to altitudinalchanges is the river continuum concept (RCC) which displays structural and functional responsesto the longitudinal gradient [49] Altitude has also been well documented in other studies as amain descriptor to determine macroinvertebrate richness as well as other environmental variablessuch as temperature hydrology food availability streambed condition and water chemistry [350]However we revealed poor relationships of altitude with water chemistry in contrast with significant

Water 2016 8 27 14 of 20

associations with physical variables and biological attributes such as taxa richness EPT richnessEPT abundance and the Shannon diversity index This may be due to the fact that over half ofthe studied streams corresponded to lowland streams below 100 m asl which were characterizedby moderate or slightly poor water quality with severe variations in BOD TN TP and Shannondiversity-based saprobity [3651] (Table 1) Harding et al [52] demonstrated that increasing humanland use intensity along a river continuum caused water quality degradation consequently leadingto changes in taxonomic composition from intolerant EPT dominated to tolerant taxa-dominatedassemblages despite a gradual increase in taxa abundance by a few dominant species

Riffle habitats are commonly characterized by shallow water depth oxygenating fast-flowingwater and stony beds and exhibit higher taxa richness and abundance than that at pools or habitatswith fine sediment as in our case [34253] Such hydraulic conditions are critical determinantsfor the distribution and species composition of benthic organisms [1654] and are the drivingforces for evolution of their morphologies and life history [11] Rheophilous (ie having an affinityfor running waters) and limnophilous taxa were clearly discriminated based on the correlationanalysis (Figure 2) and CCA (Figure 4) results For example well-known rhithronic species intwo Ephemeropteran (Ephemerellidae and Heptageniidae) and one Trichopteran (Hydropsychidae)families mostly displayed high preference to the mid- or fast current conditions which corresponds tothe intolerant scraper or filtering collector groups abundant in upper and middle stream reaches [49]Thus biological monitoring and assessment programs using rheophilic macroinvertebrates wouldbenefit from their ecological characteristics and their indication of good environmental quality(eg [42]) although seasonal fluctuations in hydraulic parameters by the Asian monsoon more criticallycause a catastrophic drift and washout of benthic organisms

Streambed composition is one of the most important factors to directly influence richness andabundance of macroinvertebrates on local scales [1216] thus close correlations would be expectedwith variables related to longitudinal changes in stream ecosystems Boulders and cobbles aretypically the major structural elements in steep gradient upper streams whereas sand and smallersediments predominate in the lower reaches [55] There have been a large number of studies onthe macroinvertebrate-substrate relationship most of which have revealed that macroinvertebratediversity and density increase with higher heterogeneity due to the available stable and diversemicrohabitats (eg [1043]) Therefore factors determining macroinvertebrate communities at localscales obviously put a priority on the streambed conditions rather than water quality or other physicalvariables We found that the mainstreams of the Nakdong River which contained about 60 fineparticles retained the lowest taxa richness (82 on average n = 18) and abundance (747 individualsm2)among five major rivers despite its good water quality condition (mean BOD 19 and TN 18 mgL)with the exception of the severely polluted Youngsan River (89 taxa richness and 73 BOD n = 13)These results indicate that homogeneous streambeds with greater fine particles support lower diversityand abundance even when streams maintain good water quality [56] Additionally organic pollutioncould transform the coarse substrate into an organic rich soft bottom altering the community structurefrom dominated by diverse and intolerant species to communities predominated by a few tolerantspecies [320] as in the case of the Youngsan River

43 Considerations to Improve Macroinvertebrate Biomonitoring Programs

Not until 2006 did Korea adopt biological water quality criteria and the concept of ecologicalintegrity in the water quality program [2536] Since then Korean government has led a biologicalsurvey of streams and rivers (ie NAEMP) every year to assess the current biological status of streamand river ecosystems and to develop a strategy for the restoration and management of disturbedsystems [25] As a part of a nationwide survey benthic macroinvertebrates are also monitored based onthe guidelines and assessment tools [27] Notwithstanding their suitability for convenient and rapidbio-assessment there remain debatable issues as to whether the methods for sampling and treating

Water 2016 8 27 15 of 20

macroinvertebrates are effective to provide a reliable and accurate indication of the macroinvertebratefauna throughout the country

The Korean national biomonitoring program presents field sampling in a cost-effective andtime-saving manner for rapid bio-assessment To satisfy this purpose benthic macroinvertebratesare optimized to be collected at riffle andor gliding run habitats using a Surber sampler with threereplicates [27] However such sampling methods probably underestimate overall biodiversity instream ecosystems considering the whole stream environment First single-habitat sampling possiblyproduces incomplete taxa lists and includes no target habitats at certain sites despite its advantagethat the influences of both water and habitat quality on macroinvertebrates are not confounded byinstream habitat variation [57] In this regard a multihabitat approach would be more profitablefor the estimation of taxonomic diversity due to its consistent application across stream typesespecially at large-scaled survey comprehensive taxa lists and effective assessment of ecologicalconditions [58] Second the Surber sampler is one of the most commonly used quantitative toolsin lotic systems and provides high-precision information on the abundance and composition ofmacroinvertebrate assemblages [2159] This method is on the other hand usually more appropriatefor riffle habitats of shallow streams presumably underestimating overall biodiversity in a regionRecent studies on the comparison between sampling devices suggested that artificial substrates(eg leaf-bags) would be used as complementary tools due to their discriminative taxonomiccomposition [60ndash62] Third a majority of biomonitoring programs widely adopt three to five replicatesfor lotic ecosystems because one way to reduce monitoring costs is to decrease the sample size [216364]The previous studies also showed that such a small number of replicates rarely influenced ecologicalhealth assessment particularly for the indices applying sensitivitytolerance taxa as the same forNAEMP [65ndash67] Nevertheless small sample sizes may influence the values of biological measuresand the representativeness for a real benthic community based on the asymptotic relationship ofthe number of taxa with both the sampling area and the collected individuals [68] Finally sievemesh size could also affect the accurate estimates of taxonomic diversity and environmental qualityassessment [67] Finer mesh sizes more accurately represent macroinvertebrate assemblages thancoarser mesh sizes whereas they need more efforts to handle specimens On the contrary coarsermesh sizes undervalue the original density and taxa richness of macroinvertebrate assemblages bypassing small individuals through the sieves and result in higher diversity [69] Considering thetradeoff between cost and effectiveness many rapid bio-assessments determine 05 mm mesh size as areasonable choice [216470] Therefore future researches are required for identifying optimal samplingeffort comprehensively considering cost-effectiveness easy applicability and well representative ofresident macroinvertebrate assemblages

5 Conclusions

Large-scale knowledge on environmental relationships of aquatic communities is crucial toconserve freshwater biodiversity and sustain ecological integrity Korean stream macroinvertebrateassemblages were determined not only by regional and physical instream variables but also bypollution-related parameters at nation-wide scale Macroinvertebrate-based site classification evidentlyprovided an environmental characterization for different types of Korean streams indicating thatbenthic macroinvertebrates are a valuable biomonitoring material The results of this study provideimportant information and a bridge for further work such as the assemblagemdashspecific responses toenvironmental disturbance Our results also contribute to establishing effective management practicesimplementing conservation measures and developing more reliable biological monitoring tools forsustainable freshwater ecosystems

Acknowledgments This study was performed under the project of ldquoNational Aquatic Ecosystem Health Surveyand Assessmentrdquo in Korea and was supported by the Ministry of Environment and the National Institute ofEnvironmental Research Korea The authors are grateful to survey members involved in the project The authorsalso thank the anonymous reviewers for their help in improving the scientific content of the manuscript

Water 2016 8 27 16 of 20

Author Contributions Yung-Chul Jun developed the concept of the study performed data analysis and wrotethe manuscript Nan-Young Kim assisted data processing and figure construction Sang-Hun Kim conductedquality assurance of the physico-chemical and biological data Young-Seuk Park and Dong-Soo Kong assistedstudy design and statistical analysis Soon-Jin Hwang supervised the research and assisted data interpretationand manuscript preparation All the authors contributed to the review of the manuscript

Conflicts of Interest The authors declare no conflict of interest

Appendix A

Table A1 Codes for macroinvertebrates contributing to more than 02 of total abundance for canonicalcorrespondence analysis in Figure 4

Code TaxonPhylum Platyhelminthes

DugSp Dugesia spPhylum Mollusca

SemLi Semisulcospira libertina (Gould)PhyAc Physa acuta Draparnaud

Phylum AnnelidaLimGo Limnodrilus gotoi HataiHirNi Hirudo nipponia Whitman

Phylum ArthropodaClass Crustacea

AseSp Asellus spGamSp Gammarus sp

Class Insecta

Order Ephemeroptera

BaeTu Baetiella tuberculata (Kazlauskas)BaeFu Baetis fuscatus (Linnaeus)BaeUr Baetis ursinus KazlauskasLabAt Labiobaetis atrebatinus (Eaton)NigBa Nigrobaetis bacillus (Kluge)EcdBa Ecdyonurus bajkovae KlugeEcdJo Ecdyonurus joernensis BengtssonEcdKi Ecdyonurus kibunensis ImanishiEcdLe Ecdyonurus levis (Navaacutes)EpeNi Epeorus nipponicus (Ueacuteno)EpeLa Epeorus latifolium (Ueacuteno)EpePe Epeorus pellucidus (Brodsky)ChoAl Choroterpes altioculus KlugeParJa Paraleptophlebia japonica (Matsumura)PotFo Potamanthus formosus EatonRhoCo Rhoenanthus coreanus (Yoon and Bae)DruAc Drunella aculea (Allen)EphOr Ephemera orientalis McLachlanSerSe Serratella setigera (Bajkova)UraPu Uracanthella punctisetae (Matsumura)CaeNi Caenis nishinoae Malzacher

Order Hemiptera

MicSe Micronecta sedula HorvaacutethMicSp Micronecta sp

Order Coleoptera

ElmSp Elmidae spEubKa Eubrianax KUaMatKa Mataeopsephus KUaPseKa Psephenoides KUa

Water 2016 8 27 17 of 20

Table A1 Cont

Code Taxon

Order Diptera

AntKa Antocha KUaCulSp Culex spChiSp Chironomidae spp (non-red type)ChiRe Chironomini spp (red-type)

Order Trichoptera

RhyNi Rhyacophila nigrocephala IwataHydKa Hydroptila KUaGloKa Glossosoma KUaCheBr Cheumatopsyche brevilineata IwataCheKa Cheumatopsyche KUaCheKb Cheumatopsyche KUbHydKo Hydropsyche kozhantschikovi MartynovHydKb Hydropsyche KUbHydOr Hydropsyche orientalis MartynovHydVa Hydropsyche valvata MartynovMacRa Macrostemum radiatum McLachlanPsySp Psychomyia sp

References

1 Dudgeon D Arthington AH Gessner MO Kawabata ZI Knowler DJ Leacutevecircque C Naiman RJPrieur-Richard AH Soto D Stiassny MLJ et al Freshwater biodiversity Importance threats status andconservation challenges Biol Rev 2006 81 163ndash182 [CrossRef] [PubMed]

2 Strayer DL Dudgeon D Freshwater biodiversity conservation Recent progress and future challengesJ N Am Benthol Soc 2010 29 344ndash358 [CrossRef]

3 Li F Chung N Bae M-J Kwon Y-S Park Y-S Relationships between stream macroinvertebrates andenvironmental variables at multiple spatial scales Freshwater Biol 2012 57 2107ndash2124 [CrossRef]

4 Dudgeon D The ecology of tropical Asian rivers and streams in relation to biodiversity conservationAnnu Rev Ecol Syst 2000 31 239ndash263 [CrossRef]

5 De Silva SS Abery NW Nguyen TTT Endemic freshwater finfish of Asia Distribution and conservationstatus Divers Distrib 2007 13 172ndash184 [CrossRef]

6 Voumlroumlsmarty CJ McIntyre PB Gessner MO Dudgeon D Prusevich A Green P Glidden S Bunn SESullivan CA Liermann CE et al Global threats to human water security and river biodiversity Nature2010 467 555ndash561 [CrossRef] [PubMed]

7 Strayer DL Challenges for freshwater invertebrate conservation J N Am Benthol Soc 2006 25 271ndash287[CrossRef]

8 Buss DF Baptista DF Silveira MP Nessimian JL Dorvilleacute LFM Influence of water chemistryand environmental degradation on macroinvertebrate assemblages in a river basin in south-east BrazilHydrobiologia 2002 481 125ndash136 [CrossRef]

9 Bott TL Brock JT Dunn CS Naiman RJ Ovink RW Petersen RC Benthic community metabolism infour temperate stream systems An inter-biome comparison and evaluation of the river continuum conceptHydrobiologia 1985 220 109ndash117 [CrossRef]

10 Merz JR Ochikubo Chan LK Effects of gravel augmentation on macroinvertebrate assemblages in aregulated California river River Res Appl 2005 21 61ndash74 [CrossRef]

11 Nelson SM Lieberman DM The influence of flow and other environmental factors on benthic invertebratesin the Sacramento River USA Hydrobiologia 2002 489 117ndash129 [CrossRef]

12 Jiang XM Xiong J Qiu JW Wu JM Wang JW Xie ZC Structure of macroinvertebrate communitiesin relation to environmental variables in a subtropical Asian river system Int Rev Hydrobiol 2010 95 42ndash57[CrossRef]

Water 2016 8 27 9 of 20

33 Macroinvertebrate-Based Site Classification

The cluster analysis based on the similarity in the benthic macroinvertebrate composition largelyclassified the 720 sampling sites into two clusters and subsequently sub-clustered them into five groupsAs a result 126 sampling sites were included in Group 1a 199 sites in Groups 1b 106 sites in Group 2a118 sites in Group 2b and 171 sites in Group 2c (Figure 1) MRPP validated these five groups withsignificant differences (A = 0484 p lt 0001) The differences in environmental variables among theclusters are shown in Figure 3 The most important indicator taxa for each cluster are shown with theirindicator values in Table 3

Figure 3 Distribution of selected environmental variables among the five clusters of the 720 samplingsites which were identified by cluster analysis with Soslashrenson distance measure Box represents the25th and 75th percentiles and whiskers indicate the 5th and 95th percentiles with standard deviations(error bar) The mean (horizontal dotted line) and median (horizontal solid line) are shown in each boxDifferent small letters indicate significant difference based on a Dunnrsquos multiple comparison test atp lt 005

Water 2016 8 27 10 of 20

Table 3 Indicator values () for the most important species (p lt 005) in each cluster group MonteCarlo tests (999 permutations) were used to assess the significance of each species as an indicator forthe respective group (G1andashG2c) In total 50 species whose contribution to total density was higher than02 were analyzed Less important species were not shown in this table

TaxaCluster Group

pG1a G1b G2a G2b G2c

Rhyacophila nigrocephala Iwata 47 16 0 0 0 0001Epeorus nipponicus (Ueacuteno) 46 1 0 0 0 0001Glossosoma KUa 44 4 0 0 0 0001Drunella aculea (Allen) 44 1 0 0 0 0001Hydropsyche orientalis Martynov 40 7 1 1 0 0001

Uracanthella punctisetae(Matsumura)

21 48 6 6 0 0001

Hydropsyche valvata Martynov 6 46 2 9 0 0001Cheumatopsyche brevilineataIwata

15 41 5 10 0 0001

Hydropsyche kozhantschikoviMartynov

21 40 3 16 0 0001

Psychomyia sp 0 32 1 5 0 0001

Ephemera orientalis McLachlan 2 20 41 5 2 0001Ecdyonurus levis (Navaacutes) 5 28 40 1 0 0001Ecdyonurus joernensis Bengtsson 0 12 25 1 0 0001Mataeopsephus KUa 0 16 23 0 0 0001Asellus sp 0 2 11 3 6 0001

Hirudo nipponia Whitman 1 10 2 28 4 0001Chironomini sp 1 7 9 27 21 0001Limnodrilus gotoi Hatai 5 12 18 23 9 0001

Micronecta sedula Horvaacuteth 0 0 0 0 20 0001Physa acuta Draparnaud 2 3 2 12 16 0001Micronecta sp 0 0 5 0 5 0007

Total number of significantindicator species

12 21 8 3 3 -

Each cluster was clearly differentiated according to the differences of instream physicochemicalconditions and geographical location of sampling sites The cluster analysis discriminated less pollutedstreams with low EC and fast flowing water (Group 1) from moderately or severely polluted steams withhigh EC and slow water velocity (Group 2) Group 1a (G1a) congregating in the HRW consisted specificallyof mountainous upper streams although a tenth of this group was scattered over the other watershedsexcept the YRW This group consisted of oligotrophic streams with distinguishing features of the highestaltitude the lowest BOD and nutrient concentrations and the fastest water velocity Additionally thecatchment was predominantly comprised of forested area The best indicator species for this group werecharacterized as high sensitivity against organic pollution (eg Rhyacophila nigrocephala Iwata Epeorusnipponicus (Ueacuteno) Drunella aculea (Allen) and Hydropsyche orientalis Martynov) Group 1b (G1b) containedthe largest number of sampling sites and was widely distributed throughout all river watersheds butmostly encompassing the agricultural and forested catchment G1a and G1b closely resembled chemicalenvironments but steam sites belonging to G1b displayed mesotrophic condition with slightly higherBOD and nutrients than those of G1a There existed the largest number of indicator species in G1b amongwhich U punctisetae showed the highest indicator value

G2a mostly included sites located in middle reaches of large rivers and their tributariesparticularly in the NRW and SRW Although Group 2a (G2a) was similar in overall environmentalcharacteristics to G1b G2a was characterized with slightly lower altitude higher EC and a lower watervelocity when compared with G1b Sampling sites suffering from poor water quality with organicdegradation and nutrient enrichment were confined to Group 2b with the highest BOD TN and TPconcentrations These sites were influenced by the highest degree of agriculture andor urbanizationThe significant indicator species of this group were Hirudo nipponia Whitman Chironomini sp and

Water 2016 8 27 11 of 20

L gotoi indicating high trophy and saprobity [35] Water quality conditions in Group 2c (G2c) were aspoor as those of G2b with the highest EC Sites in this group were characterized with the lowest watervelocity and the largest proportion of fine particles because G2c was gathered by streams adjacent toestuaries large rivers and dammed streams The only three weak indicator species appeared in G2c

34 Environmental Variables Affecting Macroinvertebrate Distributions

A CCA was performed to understand how macroinvertebrates were distributed alongenvironmental gradients (Figure 4) Total variability explained in the species data was 159 (Table 4)The eigenvalues of the first CCA axis (0281) and the second CCA axis (0101) were significant (p lt 00199 Monte Carlo permutation test) All three CCA results were significant based on a Monte Carlopermutation test (p lt 001)

Figure 4 Ordination plots constructed by canonical correspondence analysis for all sampling sites(n = 720) The plots present the ordination of sampling sites (a) and macroinvertebrates (b) with relativecontributions of environmental variables (c) for the first two axes Only species contributing gt02to total abundance were included The summary of ordination results is presented in Table 4 and thecodes for each taxon are shown in Appendix Table A1

Water 2016 8 27 12 of 20

Table 4 Spearmanrsquos rank correlation coefficients and probabilities of environmental variables andthe CCA axes ( p lt 001 p lt 005) (a) and summary of CCA results (n = 720) (b) All axes weresignificant based on Monte Carlo permutation procedures

Variables Axis 1 Axis 2 Axis 3

(a) Correlation coefficients

Altitude 0793 0236 0013Stream order acute0105 acute0658 0099

Urban acute0218 0134 acute0317 Agriculture acute0199 acute0273 0133

Forest 0504 0055 0266 Water velocity 0662 acute0054 acute0510

Fine particles acute0744 0325 acute0076 Coarse particles 0747 acute0327 0075

pH 0011 acute0236 0007DO 0304 acute0467 acute0166

BOD acute0550 0164 acute0370 EC acute0196 acute0278 acute0116 TN acute0463 0266 acute0387 TP acute0373 0229 acute0314

(b) Summary of CCA results

Eigenvalue 0281 0101 0073 variance explained in

taxa data 98 35 25

Cumulative varianceexplained 98 133 159

p value 0010 0010 0010

Total variance 2869 - -

The five clusters were well separated in the CCA ordination plot (Figure 4a) Both the G1aand G1b groups with good physicochemical environments were positioned on the right side of theordination plot and G2b and G2c were on the opposite side However the G2a group straddledboth sides Eight environmental variables (ie BOD TN TP altitude water velocity forest fineparticles and coarse particles) had significant correlations with the first axis among which altitudewas the most significant contributor (r = 0793 p lt 001) followed by coarse particles (r = 0747p lt 001) and fine particles (r = acute0744 p lt 001) (Table 4) All physical factors except for fineparticles were in the opposite direction from the chemical variables (Figure 4c) This result suggeststhat the decline in altitude reflected deterioration in water quality accompanied by increases in organicmaterial and nutrients The heterogeneity of the macroinvertebrate habitats also decreased with thelongitudinal gradient toward downstream The second axis was negatively related with stream order(r =acute0658 p lt 001) and DO (r =acute0467 p lt 001) High positive scores with the first axis were denotedfor the rhithronic (ie pertaining to the headwaters) and intolerant species (eg Drunella aculea (Allen)E nipponicus Glossosoma sp R nigrocephala Iwata and H orientalis) whereas negative scores wereobserved for the potamic (ie pertaining to rivers) and tolerant taxa (eg Micronecta sedula HorvaacutethPhysa acuta Draparnaud Labiobaetis atrebatinus (Eaton) and Asellus hilgendorfii Bovalius) (Figure 4b)

4 Discussion

The Asian monsoon region is a global biodiversity hotspot suffering from increasinganthropogenic disturbances but aquatic biodiversity and ecosystem integrity remain poorlyexplored [3] This is the same situation in Korea but recent establishment of the National AquaticEcological Monitoring Program [36] opened a new era to assess ecosystem health and biodiversityin Korea Our work presented in this paper takes advantage of the opportunity of such anationwide scale of survey Although the five river watersheds in Korea exhibited differences in

Water 2016 8 27 13 of 20

environmental conditions and macroinvertebrate taxa abundance overall taxonomic compositionat each watershed displayed little difference (Table 2) Instead a considerable spatial variation inbenthic macroinvertebrate assemblages accounted for the combination of both ultimate (eg altitudeand the degree of land use) and proximate factors (eg flow stream bed substrate BOD EC andnutrients) This finding was in line with previous studies of benthic diatoms in Korea [25] andmacroinvertebrates in other Asian countries [1237] suggesting the importance of various multi-scalefactors in structuring macroinvertebrate assemblages [38] Our results provide basal information forthe sustainable management and conservation practices of stream ecosystems

41 Macroinvertebrate Taxonomic Composition

The macroinvertebrate assemblages in Korean stream ecosystems generally bear resemblance tothose in tropical and other temperate streams at higher taxonomic levels [3539] However temperateKorean streams were relatively rich in Ephemeroptera Diptera and Trichoptera when comparedwith tropical streams for the higher biodiversity of Gastropoda Decapoda and other insect orderssuch as Odonata and Hemiptera [3940] (Table 2) The taxonomic composition also included a largenumber of rhithronic fauna that prefer stony substrates For example Baetidae Heptageniidae andEphemerellidae mainly dominated the Ephemeroptera and Rhyacophilidae and Hydropsychidaecomposed the Trichoptera in this study

We confirmed a total of 340 macroinvertebrate taxa in this study Of the macroinvertebrate taxachironomid midge larvae and a small minnow mayfly (B fuscatus) were extensively encounteredthroughout Korean stream environments with the highest occurring frequency with 94 and 76of total sampling sites respectively Temperate Korean streams were also characterized with a fewpredominant colonizers and a majority of rare taxa in macroinvertebrate taxonomic compositionMoreover only six cosmopolitan taxa were noticeably comprised of gt60 of all macroinvertebratesamples which were L gotoi Chironomidae spp U punctisetae C brevilineata H valvata andH kozhantschikovi These dominant taxa were found to be significant indicators of mesotrophicor polytrophic streams in our study (Table 3) consistent with a result that most Korean streams andrivers were degraded in both chemical and biological status [36] On the other hand most Koreanstreams were occupied by a great number of rare macroinvertebrate species with a small distributionrange andor low abundance as was also demonstrated in other studies [4142]

42 Environmental Relationships with Macroinvertebrate Distribution

Benthic habitats are complex and a variety of environmental variables acting at multiple spatialscales regulate the composition and distribution patterns of stream macroinvertebrate assemblagesin an exclusive or synergistic fashion [3843] We revealed that the variables associated with altitudeand in-stream habitats best accounted for the largest amount of variability in our macroinvertebratedata set supporting the more important determinants of local environmental factors than broad orregional parameters [1644] The importance and role of local environmental variables have also beenhighlighted in other aquatic communities aquatic macrophytes [45] freshwater phytoplankton [46]benthic diatoms [44] intertidal macroinvertebrates [47] and fish [48] However a comprehensiveunderstanding of multispatial scales is needed because of significant correlations between macrohabitatand microhabitat characteristics depending on the relative size of the area studied [3]

In our study the variability among the macroinvertebrate-based stream groups was moreprominently explained by the altitudinal gradients together with streambed composition and watervelocity than chemical variables (Table 3) First the most widely accepted theory related to altitudinalchanges is the river continuum concept (RCC) which displays structural and functional responsesto the longitudinal gradient [49] Altitude has also been well documented in other studies as amain descriptor to determine macroinvertebrate richness as well as other environmental variablessuch as temperature hydrology food availability streambed condition and water chemistry [350]However we revealed poor relationships of altitude with water chemistry in contrast with significant

Water 2016 8 27 14 of 20

associations with physical variables and biological attributes such as taxa richness EPT richnessEPT abundance and the Shannon diversity index This may be due to the fact that over half ofthe studied streams corresponded to lowland streams below 100 m asl which were characterizedby moderate or slightly poor water quality with severe variations in BOD TN TP and Shannondiversity-based saprobity [3651] (Table 1) Harding et al [52] demonstrated that increasing humanland use intensity along a river continuum caused water quality degradation consequently leadingto changes in taxonomic composition from intolerant EPT dominated to tolerant taxa-dominatedassemblages despite a gradual increase in taxa abundance by a few dominant species

Riffle habitats are commonly characterized by shallow water depth oxygenating fast-flowingwater and stony beds and exhibit higher taxa richness and abundance than that at pools or habitatswith fine sediment as in our case [34253] Such hydraulic conditions are critical determinantsfor the distribution and species composition of benthic organisms [1654] and are the drivingforces for evolution of their morphologies and life history [11] Rheophilous (ie having an affinityfor running waters) and limnophilous taxa were clearly discriminated based on the correlationanalysis (Figure 2) and CCA (Figure 4) results For example well-known rhithronic species intwo Ephemeropteran (Ephemerellidae and Heptageniidae) and one Trichopteran (Hydropsychidae)families mostly displayed high preference to the mid- or fast current conditions which corresponds tothe intolerant scraper or filtering collector groups abundant in upper and middle stream reaches [49]Thus biological monitoring and assessment programs using rheophilic macroinvertebrates wouldbenefit from their ecological characteristics and their indication of good environmental quality(eg [42]) although seasonal fluctuations in hydraulic parameters by the Asian monsoon more criticallycause a catastrophic drift and washout of benthic organisms

Streambed composition is one of the most important factors to directly influence richness andabundance of macroinvertebrates on local scales [1216] thus close correlations would be expectedwith variables related to longitudinal changes in stream ecosystems Boulders and cobbles aretypically the major structural elements in steep gradient upper streams whereas sand and smallersediments predominate in the lower reaches [55] There have been a large number of studies onthe macroinvertebrate-substrate relationship most of which have revealed that macroinvertebratediversity and density increase with higher heterogeneity due to the available stable and diversemicrohabitats (eg [1043]) Therefore factors determining macroinvertebrate communities at localscales obviously put a priority on the streambed conditions rather than water quality or other physicalvariables We found that the mainstreams of the Nakdong River which contained about 60 fineparticles retained the lowest taxa richness (82 on average n = 18) and abundance (747 individualsm2)among five major rivers despite its good water quality condition (mean BOD 19 and TN 18 mgL)with the exception of the severely polluted Youngsan River (89 taxa richness and 73 BOD n = 13)These results indicate that homogeneous streambeds with greater fine particles support lower diversityand abundance even when streams maintain good water quality [56] Additionally organic pollutioncould transform the coarse substrate into an organic rich soft bottom altering the community structurefrom dominated by diverse and intolerant species to communities predominated by a few tolerantspecies [320] as in the case of the Youngsan River

43 Considerations to Improve Macroinvertebrate Biomonitoring Programs

Not until 2006 did Korea adopt biological water quality criteria and the concept of ecologicalintegrity in the water quality program [2536] Since then Korean government has led a biologicalsurvey of streams and rivers (ie NAEMP) every year to assess the current biological status of streamand river ecosystems and to develop a strategy for the restoration and management of disturbedsystems [25] As a part of a nationwide survey benthic macroinvertebrates are also monitored based onthe guidelines and assessment tools [27] Notwithstanding their suitability for convenient and rapidbio-assessment there remain debatable issues as to whether the methods for sampling and treating

Water 2016 8 27 15 of 20

macroinvertebrates are effective to provide a reliable and accurate indication of the macroinvertebratefauna throughout the country

The Korean national biomonitoring program presents field sampling in a cost-effective andtime-saving manner for rapid bio-assessment To satisfy this purpose benthic macroinvertebratesare optimized to be collected at riffle andor gliding run habitats using a Surber sampler with threereplicates [27] However such sampling methods probably underestimate overall biodiversity instream ecosystems considering the whole stream environment First single-habitat sampling possiblyproduces incomplete taxa lists and includes no target habitats at certain sites despite its advantagethat the influences of both water and habitat quality on macroinvertebrates are not confounded byinstream habitat variation [57] In this regard a multihabitat approach would be more profitablefor the estimation of taxonomic diversity due to its consistent application across stream typesespecially at large-scaled survey comprehensive taxa lists and effective assessment of ecologicalconditions [58] Second the Surber sampler is one of the most commonly used quantitative toolsin lotic systems and provides high-precision information on the abundance and composition ofmacroinvertebrate assemblages [2159] This method is on the other hand usually more appropriatefor riffle habitats of shallow streams presumably underestimating overall biodiversity in a regionRecent studies on the comparison between sampling devices suggested that artificial substrates(eg leaf-bags) would be used as complementary tools due to their discriminative taxonomiccomposition [60ndash62] Third a majority of biomonitoring programs widely adopt three to five replicatesfor lotic ecosystems because one way to reduce monitoring costs is to decrease the sample size [216364]The previous studies also showed that such a small number of replicates rarely influenced ecologicalhealth assessment particularly for the indices applying sensitivitytolerance taxa as the same forNAEMP [65ndash67] Nevertheless small sample sizes may influence the values of biological measuresand the representativeness for a real benthic community based on the asymptotic relationship ofthe number of taxa with both the sampling area and the collected individuals [68] Finally sievemesh size could also affect the accurate estimates of taxonomic diversity and environmental qualityassessment [67] Finer mesh sizes more accurately represent macroinvertebrate assemblages thancoarser mesh sizes whereas they need more efforts to handle specimens On the contrary coarsermesh sizes undervalue the original density and taxa richness of macroinvertebrate assemblages bypassing small individuals through the sieves and result in higher diversity [69] Considering thetradeoff between cost and effectiveness many rapid bio-assessments determine 05 mm mesh size as areasonable choice [216470] Therefore future researches are required for identifying optimal samplingeffort comprehensively considering cost-effectiveness easy applicability and well representative ofresident macroinvertebrate assemblages

5 Conclusions

Large-scale knowledge on environmental relationships of aquatic communities is crucial toconserve freshwater biodiversity and sustain ecological integrity Korean stream macroinvertebrateassemblages were determined not only by regional and physical instream variables but also bypollution-related parameters at nation-wide scale Macroinvertebrate-based site classification evidentlyprovided an environmental characterization for different types of Korean streams indicating thatbenthic macroinvertebrates are a valuable biomonitoring material The results of this study provideimportant information and a bridge for further work such as the assemblagemdashspecific responses toenvironmental disturbance Our results also contribute to establishing effective management practicesimplementing conservation measures and developing more reliable biological monitoring tools forsustainable freshwater ecosystems

Acknowledgments This study was performed under the project of ldquoNational Aquatic Ecosystem Health Surveyand Assessmentrdquo in Korea and was supported by the Ministry of Environment and the National Institute ofEnvironmental Research Korea The authors are grateful to survey members involved in the project The authorsalso thank the anonymous reviewers for their help in improving the scientific content of the manuscript

Water 2016 8 27 16 of 20

Author Contributions Yung-Chul Jun developed the concept of the study performed data analysis and wrotethe manuscript Nan-Young Kim assisted data processing and figure construction Sang-Hun Kim conductedquality assurance of the physico-chemical and biological data Young-Seuk Park and Dong-Soo Kong assistedstudy design and statistical analysis Soon-Jin Hwang supervised the research and assisted data interpretationand manuscript preparation All the authors contributed to the review of the manuscript

Conflicts of Interest The authors declare no conflict of interest

Appendix A

Table A1 Codes for macroinvertebrates contributing to more than 02 of total abundance for canonicalcorrespondence analysis in Figure 4

Code TaxonPhylum Platyhelminthes

DugSp Dugesia spPhylum Mollusca

SemLi Semisulcospira libertina (Gould)PhyAc Physa acuta Draparnaud

Phylum AnnelidaLimGo Limnodrilus gotoi HataiHirNi Hirudo nipponia Whitman

Phylum ArthropodaClass Crustacea

AseSp Asellus spGamSp Gammarus sp

Class Insecta

Order Ephemeroptera

BaeTu Baetiella tuberculata (Kazlauskas)BaeFu Baetis fuscatus (Linnaeus)BaeUr Baetis ursinus KazlauskasLabAt Labiobaetis atrebatinus (Eaton)NigBa Nigrobaetis bacillus (Kluge)EcdBa Ecdyonurus bajkovae KlugeEcdJo Ecdyonurus joernensis BengtssonEcdKi Ecdyonurus kibunensis ImanishiEcdLe Ecdyonurus levis (Navaacutes)EpeNi Epeorus nipponicus (Ueacuteno)EpeLa Epeorus latifolium (Ueacuteno)EpePe Epeorus pellucidus (Brodsky)ChoAl Choroterpes altioculus KlugeParJa Paraleptophlebia japonica (Matsumura)PotFo Potamanthus formosus EatonRhoCo Rhoenanthus coreanus (Yoon and Bae)DruAc Drunella aculea (Allen)EphOr Ephemera orientalis McLachlanSerSe Serratella setigera (Bajkova)UraPu Uracanthella punctisetae (Matsumura)CaeNi Caenis nishinoae Malzacher

Order Hemiptera

MicSe Micronecta sedula HorvaacutethMicSp Micronecta sp

Order Coleoptera

ElmSp Elmidae spEubKa Eubrianax KUaMatKa Mataeopsephus KUaPseKa Psephenoides KUa

Water 2016 8 27 17 of 20

Table A1 Cont

Code Taxon

Order Diptera

AntKa Antocha KUaCulSp Culex spChiSp Chironomidae spp (non-red type)ChiRe Chironomini spp (red-type)

Order Trichoptera

RhyNi Rhyacophila nigrocephala IwataHydKa Hydroptila KUaGloKa Glossosoma KUaCheBr Cheumatopsyche brevilineata IwataCheKa Cheumatopsyche KUaCheKb Cheumatopsyche KUbHydKo Hydropsyche kozhantschikovi MartynovHydKb Hydropsyche KUbHydOr Hydropsyche orientalis MartynovHydVa Hydropsyche valvata MartynovMacRa Macrostemum radiatum McLachlanPsySp Psychomyia sp

References

1 Dudgeon D Arthington AH Gessner MO Kawabata ZI Knowler DJ Leacutevecircque C Naiman RJPrieur-Richard AH Soto D Stiassny MLJ et al Freshwater biodiversity Importance threats status andconservation challenges Biol Rev 2006 81 163ndash182 [CrossRef] [PubMed]

2 Strayer DL Dudgeon D Freshwater biodiversity conservation Recent progress and future challengesJ N Am Benthol Soc 2010 29 344ndash358 [CrossRef]

3 Li F Chung N Bae M-J Kwon Y-S Park Y-S Relationships between stream macroinvertebrates andenvironmental variables at multiple spatial scales Freshwater Biol 2012 57 2107ndash2124 [CrossRef]

4 Dudgeon D The ecology of tropical Asian rivers and streams in relation to biodiversity conservationAnnu Rev Ecol Syst 2000 31 239ndash263 [CrossRef]

5 De Silva SS Abery NW Nguyen TTT Endemic freshwater finfish of Asia Distribution and conservationstatus Divers Distrib 2007 13 172ndash184 [CrossRef]

6 Voumlroumlsmarty CJ McIntyre PB Gessner MO Dudgeon D Prusevich A Green P Glidden S Bunn SESullivan CA Liermann CE et al Global threats to human water security and river biodiversity Nature2010 467 555ndash561 [CrossRef] [PubMed]

7 Strayer DL Challenges for freshwater invertebrate conservation J N Am Benthol Soc 2006 25 271ndash287[CrossRef]

8 Buss DF Baptista DF Silveira MP Nessimian JL Dorvilleacute LFM Influence of water chemistryand environmental degradation on macroinvertebrate assemblages in a river basin in south-east BrazilHydrobiologia 2002 481 125ndash136 [CrossRef]

9 Bott TL Brock JT Dunn CS Naiman RJ Ovink RW Petersen RC Benthic community metabolism infour temperate stream systems An inter-biome comparison and evaluation of the river continuum conceptHydrobiologia 1985 220 109ndash117 [CrossRef]

10 Merz JR Ochikubo Chan LK Effects of gravel augmentation on macroinvertebrate assemblages in aregulated California river River Res Appl 2005 21 61ndash74 [CrossRef]

11 Nelson SM Lieberman DM The influence of flow and other environmental factors on benthic invertebratesin the Sacramento River USA Hydrobiologia 2002 489 117ndash129 [CrossRef]

12 Jiang XM Xiong J Qiu JW Wu JM Wang JW Xie ZC Structure of macroinvertebrate communitiesin relation to environmental variables in a subtropical Asian river system Int Rev Hydrobiol 2010 95 42ndash57[CrossRef]

Water 2016 8 27 10 of 20

Table 3 Indicator values () for the most important species (p lt 005) in each cluster group MonteCarlo tests (999 permutations) were used to assess the significance of each species as an indicator forthe respective group (G1andashG2c) In total 50 species whose contribution to total density was higher than02 were analyzed Less important species were not shown in this table

TaxaCluster Group

pG1a G1b G2a G2b G2c

Rhyacophila nigrocephala Iwata 47 16 0 0 0 0001Epeorus nipponicus (Ueacuteno) 46 1 0 0 0 0001Glossosoma KUa 44 4 0 0 0 0001Drunella aculea (Allen) 44 1 0 0 0 0001Hydropsyche orientalis Martynov 40 7 1 1 0 0001

Uracanthella punctisetae(Matsumura)

21 48 6 6 0 0001

Hydropsyche valvata Martynov 6 46 2 9 0 0001Cheumatopsyche brevilineataIwata

15 41 5 10 0 0001

Hydropsyche kozhantschikoviMartynov

21 40 3 16 0 0001

Psychomyia sp 0 32 1 5 0 0001

Ephemera orientalis McLachlan 2 20 41 5 2 0001Ecdyonurus levis (Navaacutes) 5 28 40 1 0 0001Ecdyonurus joernensis Bengtsson 0 12 25 1 0 0001Mataeopsephus KUa 0 16 23 0 0 0001Asellus sp 0 2 11 3 6 0001

Hirudo nipponia Whitman 1 10 2 28 4 0001Chironomini sp 1 7 9 27 21 0001Limnodrilus gotoi Hatai 5 12 18 23 9 0001

Micronecta sedula Horvaacuteth 0 0 0 0 20 0001Physa acuta Draparnaud 2 3 2 12 16 0001Micronecta sp 0 0 5 0 5 0007

Total number of significantindicator species

12 21 8 3 3 -

Each cluster was clearly differentiated according to the differences of instream physicochemicalconditions and geographical location of sampling sites The cluster analysis discriminated less pollutedstreams with low EC and fast flowing water (Group 1) from moderately or severely polluted steams withhigh EC and slow water velocity (Group 2) Group 1a (G1a) congregating in the HRW consisted specificallyof mountainous upper streams although a tenth of this group was scattered over the other watershedsexcept the YRW This group consisted of oligotrophic streams with distinguishing features of the highestaltitude the lowest BOD and nutrient concentrations and the fastest water velocity Additionally thecatchment was predominantly comprised of forested area The best indicator species for this group werecharacterized as high sensitivity against organic pollution (eg Rhyacophila nigrocephala Iwata Epeorusnipponicus (Ueacuteno) Drunella aculea (Allen) and Hydropsyche orientalis Martynov) Group 1b (G1b) containedthe largest number of sampling sites and was widely distributed throughout all river watersheds butmostly encompassing the agricultural and forested catchment G1a and G1b closely resembled chemicalenvironments but steam sites belonging to G1b displayed mesotrophic condition with slightly higherBOD and nutrients than those of G1a There existed the largest number of indicator species in G1b amongwhich U punctisetae showed the highest indicator value

G2a mostly included sites located in middle reaches of large rivers and their tributariesparticularly in the NRW and SRW Although Group 2a (G2a) was similar in overall environmentalcharacteristics to G1b G2a was characterized with slightly lower altitude higher EC and a lower watervelocity when compared with G1b Sampling sites suffering from poor water quality with organicdegradation and nutrient enrichment were confined to Group 2b with the highest BOD TN and TPconcentrations These sites were influenced by the highest degree of agriculture andor urbanizationThe significant indicator species of this group were Hirudo nipponia Whitman Chironomini sp and

Water 2016 8 27 11 of 20

L gotoi indicating high trophy and saprobity [35] Water quality conditions in Group 2c (G2c) were aspoor as those of G2b with the highest EC Sites in this group were characterized with the lowest watervelocity and the largest proportion of fine particles because G2c was gathered by streams adjacent toestuaries large rivers and dammed streams The only three weak indicator species appeared in G2c

34 Environmental Variables Affecting Macroinvertebrate Distributions

A CCA was performed to understand how macroinvertebrates were distributed alongenvironmental gradients (Figure 4) Total variability explained in the species data was 159 (Table 4)The eigenvalues of the first CCA axis (0281) and the second CCA axis (0101) were significant (p lt 00199 Monte Carlo permutation test) All three CCA results were significant based on a Monte Carlopermutation test (p lt 001)

Figure 4 Ordination plots constructed by canonical correspondence analysis for all sampling sites(n = 720) The plots present the ordination of sampling sites (a) and macroinvertebrates (b) with relativecontributions of environmental variables (c) for the first two axes Only species contributing gt02to total abundance were included The summary of ordination results is presented in Table 4 and thecodes for each taxon are shown in Appendix Table A1

Water 2016 8 27 12 of 20

Table 4 Spearmanrsquos rank correlation coefficients and probabilities of environmental variables andthe CCA axes ( p lt 001 p lt 005) (a) and summary of CCA results (n = 720) (b) All axes weresignificant based on Monte Carlo permutation procedures

Variables Axis 1 Axis 2 Axis 3

(a) Correlation coefficients

Altitude 0793 0236 0013Stream order acute0105 acute0658 0099

Urban acute0218 0134 acute0317 Agriculture acute0199 acute0273 0133

Forest 0504 0055 0266 Water velocity 0662 acute0054 acute0510

Fine particles acute0744 0325 acute0076 Coarse particles 0747 acute0327 0075

pH 0011 acute0236 0007DO 0304 acute0467 acute0166

BOD acute0550 0164 acute0370 EC acute0196 acute0278 acute0116 TN acute0463 0266 acute0387 TP acute0373 0229 acute0314

(b) Summary of CCA results

Eigenvalue 0281 0101 0073 variance explained in

taxa data 98 35 25

Cumulative varianceexplained 98 133 159

p value 0010 0010 0010

Total variance 2869 - -

The five clusters were well separated in the CCA ordination plot (Figure 4a) Both the G1aand G1b groups with good physicochemical environments were positioned on the right side of theordination plot and G2b and G2c were on the opposite side However the G2a group straddledboth sides Eight environmental variables (ie BOD TN TP altitude water velocity forest fineparticles and coarse particles) had significant correlations with the first axis among which altitudewas the most significant contributor (r = 0793 p lt 001) followed by coarse particles (r = 0747p lt 001) and fine particles (r = acute0744 p lt 001) (Table 4) All physical factors except for fineparticles were in the opposite direction from the chemical variables (Figure 4c) This result suggeststhat the decline in altitude reflected deterioration in water quality accompanied by increases in organicmaterial and nutrients The heterogeneity of the macroinvertebrate habitats also decreased with thelongitudinal gradient toward downstream The second axis was negatively related with stream order(r =acute0658 p lt 001) and DO (r =acute0467 p lt 001) High positive scores with the first axis were denotedfor the rhithronic (ie pertaining to the headwaters) and intolerant species (eg Drunella aculea (Allen)E nipponicus Glossosoma sp R nigrocephala Iwata and H orientalis) whereas negative scores wereobserved for the potamic (ie pertaining to rivers) and tolerant taxa (eg Micronecta sedula HorvaacutethPhysa acuta Draparnaud Labiobaetis atrebatinus (Eaton) and Asellus hilgendorfii Bovalius) (Figure 4b)

4 Discussion

The Asian monsoon region is a global biodiversity hotspot suffering from increasinganthropogenic disturbances but aquatic biodiversity and ecosystem integrity remain poorlyexplored [3] This is the same situation in Korea but recent establishment of the National AquaticEcological Monitoring Program [36] opened a new era to assess ecosystem health and biodiversityin Korea Our work presented in this paper takes advantage of the opportunity of such anationwide scale of survey Although the five river watersheds in Korea exhibited differences in

Water 2016 8 27 13 of 20

environmental conditions and macroinvertebrate taxa abundance overall taxonomic compositionat each watershed displayed little difference (Table 2) Instead a considerable spatial variation inbenthic macroinvertebrate assemblages accounted for the combination of both ultimate (eg altitudeand the degree of land use) and proximate factors (eg flow stream bed substrate BOD EC andnutrients) This finding was in line with previous studies of benthic diatoms in Korea [25] andmacroinvertebrates in other Asian countries [1237] suggesting the importance of various multi-scalefactors in structuring macroinvertebrate assemblages [38] Our results provide basal information forthe sustainable management and conservation practices of stream ecosystems

41 Macroinvertebrate Taxonomic Composition

The macroinvertebrate assemblages in Korean stream ecosystems generally bear resemblance tothose in tropical and other temperate streams at higher taxonomic levels [3539] However temperateKorean streams were relatively rich in Ephemeroptera Diptera and Trichoptera when comparedwith tropical streams for the higher biodiversity of Gastropoda Decapoda and other insect orderssuch as Odonata and Hemiptera [3940] (Table 2) The taxonomic composition also included a largenumber of rhithronic fauna that prefer stony substrates For example Baetidae Heptageniidae andEphemerellidae mainly dominated the Ephemeroptera and Rhyacophilidae and Hydropsychidaecomposed the Trichoptera in this study

We confirmed a total of 340 macroinvertebrate taxa in this study Of the macroinvertebrate taxachironomid midge larvae and a small minnow mayfly (B fuscatus) were extensively encounteredthroughout Korean stream environments with the highest occurring frequency with 94 and 76of total sampling sites respectively Temperate Korean streams were also characterized with a fewpredominant colonizers and a majority of rare taxa in macroinvertebrate taxonomic compositionMoreover only six cosmopolitan taxa were noticeably comprised of gt60 of all macroinvertebratesamples which were L gotoi Chironomidae spp U punctisetae C brevilineata H valvata andH kozhantschikovi These dominant taxa were found to be significant indicators of mesotrophicor polytrophic streams in our study (Table 3) consistent with a result that most Korean streams andrivers were degraded in both chemical and biological status [36] On the other hand most Koreanstreams were occupied by a great number of rare macroinvertebrate species with a small distributionrange andor low abundance as was also demonstrated in other studies [4142]

42 Environmental Relationships with Macroinvertebrate Distribution

Benthic habitats are complex and a variety of environmental variables acting at multiple spatialscales regulate the composition and distribution patterns of stream macroinvertebrate assemblagesin an exclusive or synergistic fashion [3843] We revealed that the variables associated with altitudeand in-stream habitats best accounted for the largest amount of variability in our macroinvertebratedata set supporting the more important determinants of local environmental factors than broad orregional parameters [1644] The importance and role of local environmental variables have also beenhighlighted in other aquatic communities aquatic macrophytes [45] freshwater phytoplankton [46]benthic diatoms [44] intertidal macroinvertebrates [47] and fish [48] However a comprehensiveunderstanding of multispatial scales is needed because of significant correlations between macrohabitatand microhabitat characteristics depending on the relative size of the area studied [3]

In our study the variability among the macroinvertebrate-based stream groups was moreprominently explained by the altitudinal gradients together with streambed composition and watervelocity than chemical variables (Table 3) First the most widely accepted theory related to altitudinalchanges is the river continuum concept (RCC) which displays structural and functional responsesto the longitudinal gradient [49] Altitude has also been well documented in other studies as amain descriptor to determine macroinvertebrate richness as well as other environmental variablessuch as temperature hydrology food availability streambed condition and water chemistry [350]However we revealed poor relationships of altitude with water chemistry in contrast with significant

Water 2016 8 27 14 of 20

associations with physical variables and biological attributes such as taxa richness EPT richnessEPT abundance and the Shannon diversity index This may be due to the fact that over half ofthe studied streams corresponded to lowland streams below 100 m asl which were characterizedby moderate or slightly poor water quality with severe variations in BOD TN TP and Shannondiversity-based saprobity [3651] (Table 1) Harding et al [52] demonstrated that increasing humanland use intensity along a river continuum caused water quality degradation consequently leadingto changes in taxonomic composition from intolerant EPT dominated to tolerant taxa-dominatedassemblages despite a gradual increase in taxa abundance by a few dominant species

Riffle habitats are commonly characterized by shallow water depth oxygenating fast-flowingwater and stony beds and exhibit higher taxa richness and abundance than that at pools or habitatswith fine sediment as in our case [34253] Such hydraulic conditions are critical determinantsfor the distribution and species composition of benthic organisms [1654] and are the drivingforces for evolution of their morphologies and life history [11] Rheophilous (ie having an affinityfor running waters) and limnophilous taxa were clearly discriminated based on the correlationanalysis (Figure 2) and CCA (Figure 4) results For example well-known rhithronic species intwo Ephemeropteran (Ephemerellidae and Heptageniidae) and one Trichopteran (Hydropsychidae)families mostly displayed high preference to the mid- or fast current conditions which corresponds tothe intolerant scraper or filtering collector groups abundant in upper and middle stream reaches [49]Thus biological monitoring and assessment programs using rheophilic macroinvertebrates wouldbenefit from their ecological characteristics and their indication of good environmental quality(eg [42]) although seasonal fluctuations in hydraulic parameters by the Asian monsoon more criticallycause a catastrophic drift and washout of benthic organisms

Streambed composition is one of the most important factors to directly influence richness andabundance of macroinvertebrates on local scales [1216] thus close correlations would be expectedwith variables related to longitudinal changes in stream ecosystems Boulders and cobbles aretypically the major structural elements in steep gradient upper streams whereas sand and smallersediments predominate in the lower reaches [55] There have been a large number of studies onthe macroinvertebrate-substrate relationship most of which have revealed that macroinvertebratediversity and density increase with higher heterogeneity due to the available stable and diversemicrohabitats (eg [1043]) Therefore factors determining macroinvertebrate communities at localscales obviously put a priority on the streambed conditions rather than water quality or other physicalvariables We found that the mainstreams of the Nakdong River which contained about 60 fineparticles retained the lowest taxa richness (82 on average n = 18) and abundance (747 individualsm2)among five major rivers despite its good water quality condition (mean BOD 19 and TN 18 mgL)with the exception of the severely polluted Youngsan River (89 taxa richness and 73 BOD n = 13)These results indicate that homogeneous streambeds with greater fine particles support lower diversityand abundance even when streams maintain good water quality [56] Additionally organic pollutioncould transform the coarse substrate into an organic rich soft bottom altering the community structurefrom dominated by diverse and intolerant species to communities predominated by a few tolerantspecies [320] as in the case of the Youngsan River

43 Considerations to Improve Macroinvertebrate Biomonitoring Programs

Not until 2006 did Korea adopt biological water quality criteria and the concept of ecologicalintegrity in the water quality program [2536] Since then Korean government has led a biologicalsurvey of streams and rivers (ie NAEMP) every year to assess the current biological status of streamand river ecosystems and to develop a strategy for the restoration and management of disturbedsystems [25] As a part of a nationwide survey benthic macroinvertebrates are also monitored based onthe guidelines and assessment tools [27] Notwithstanding their suitability for convenient and rapidbio-assessment there remain debatable issues as to whether the methods for sampling and treating

Water 2016 8 27 15 of 20

macroinvertebrates are effective to provide a reliable and accurate indication of the macroinvertebratefauna throughout the country

The Korean national biomonitoring program presents field sampling in a cost-effective andtime-saving manner for rapid bio-assessment To satisfy this purpose benthic macroinvertebratesare optimized to be collected at riffle andor gliding run habitats using a Surber sampler with threereplicates [27] However such sampling methods probably underestimate overall biodiversity instream ecosystems considering the whole stream environment First single-habitat sampling possiblyproduces incomplete taxa lists and includes no target habitats at certain sites despite its advantagethat the influences of both water and habitat quality on macroinvertebrates are not confounded byinstream habitat variation [57] In this regard a multihabitat approach would be more profitablefor the estimation of taxonomic diversity due to its consistent application across stream typesespecially at large-scaled survey comprehensive taxa lists and effective assessment of ecologicalconditions [58] Second the Surber sampler is one of the most commonly used quantitative toolsin lotic systems and provides high-precision information on the abundance and composition ofmacroinvertebrate assemblages [2159] This method is on the other hand usually more appropriatefor riffle habitats of shallow streams presumably underestimating overall biodiversity in a regionRecent studies on the comparison between sampling devices suggested that artificial substrates(eg leaf-bags) would be used as complementary tools due to their discriminative taxonomiccomposition [60ndash62] Third a majority of biomonitoring programs widely adopt three to five replicatesfor lotic ecosystems because one way to reduce monitoring costs is to decrease the sample size [216364]The previous studies also showed that such a small number of replicates rarely influenced ecologicalhealth assessment particularly for the indices applying sensitivitytolerance taxa as the same forNAEMP [65ndash67] Nevertheless small sample sizes may influence the values of biological measuresand the representativeness for a real benthic community based on the asymptotic relationship ofthe number of taxa with both the sampling area and the collected individuals [68] Finally sievemesh size could also affect the accurate estimates of taxonomic diversity and environmental qualityassessment [67] Finer mesh sizes more accurately represent macroinvertebrate assemblages thancoarser mesh sizes whereas they need more efforts to handle specimens On the contrary coarsermesh sizes undervalue the original density and taxa richness of macroinvertebrate assemblages bypassing small individuals through the sieves and result in higher diversity [69] Considering thetradeoff between cost and effectiveness many rapid bio-assessments determine 05 mm mesh size as areasonable choice [216470] Therefore future researches are required for identifying optimal samplingeffort comprehensively considering cost-effectiveness easy applicability and well representative ofresident macroinvertebrate assemblages

5 Conclusions

Large-scale knowledge on environmental relationships of aquatic communities is crucial toconserve freshwater biodiversity and sustain ecological integrity Korean stream macroinvertebrateassemblages were determined not only by regional and physical instream variables but also bypollution-related parameters at nation-wide scale Macroinvertebrate-based site classification evidentlyprovided an environmental characterization for different types of Korean streams indicating thatbenthic macroinvertebrates are a valuable biomonitoring material The results of this study provideimportant information and a bridge for further work such as the assemblagemdashspecific responses toenvironmental disturbance Our results also contribute to establishing effective management practicesimplementing conservation measures and developing more reliable biological monitoring tools forsustainable freshwater ecosystems

Acknowledgments This study was performed under the project of ldquoNational Aquatic Ecosystem Health Surveyand Assessmentrdquo in Korea and was supported by the Ministry of Environment and the National Institute ofEnvironmental Research Korea The authors are grateful to survey members involved in the project The authorsalso thank the anonymous reviewers for their help in improving the scientific content of the manuscript

Water 2016 8 27 16 of 20

Author Contributions Yung-Chul Jun developed the concept of the study performed data analysis and wrotethe manuscript Nan-Young Kim assisted data processing and figure construction Sang-Hun Kim conductedquality assurance of the physico-chemical and biological data Young-Seuk Park and Dong-Soo Kong assistedstudy design and statistical analysis Soon-Jin Hwang supervised the research and assisted data interpretationand manuscript preparation All the authors contributed to the review of the manuscript

Conflicts of Interest The authors declare no conflict of interest

Appendix A

Table A1 Codes for macroinvertebrates contributing to more than 02 of total abundance for canonicalcorrespondence analysis in Figure 4

Code TaxonPhylum Platyhelminthes

DugSp Dugesia spPhylum Mollusca

SemLi Semisulcospira libertina (Gould)PhyAc Physa acuta Draparnaud

Phylum AnnelidaLimGo Limnodrilus gotoi HataiHirNi Hirudo nipponia Whitman

Phylum ArthropodaClass Crustacea

AseSp Asellus spGamSp Gammarus sp

Class Insecta

Order Ephemeroptera

BaeTu Baetiella tuberculata (Kazlauskas)BaeFu Baetis fuscatus (Linnaeus)BaeUr Baetis ursinus KazlauskasLabAt Labiobaetis atrebatinus (Eaton)NigBa Nigrobaetis bacillus (Kluge)EcdBa Ecdyonurus bajkovae KlugeEcdJo Ecdyonurus joernensis BengtssonEcdKi Ecdyonurus kibunensis ImanishiEcdLe Ecdyonurus levis (Navaacutes)EpeNi Epeorus nipponicus (Ueacuteno)EpeLa Epeorus latifolium (Ueacuteno)EpePe Epeorus pellucidus (Brodsky)ChoAl Choroterpes altioculus KlugeParJa Paraleptophlebia japonica (Matsumura)PotFo Potamanthus formosus EatonRhoCo Rhoenanthus coreanus (Yoon and Bae)DruAc Drunella aculea (Allen)EphOr Ephemera orientalis McLachlanSerSe Serratella setigera (Bajkova)UraPu Uracanthella punctisetae (Matsumura)CaeNi Caenis nishinoae Malzacher

Order Hemiptera

MicSe Micronecta sedula HorvaacutethMicSp Micronecta sp

Order Coleoptera

ElmSp Elmidae spEubKa Eubrianax KUaMatKa Mataeopsephus KUaPseKa Psephenoides KUa

Water 2016 8 27 17 of 20

Table A1 Cont

Code Taxon

Order Diptera

AntKa Antocha KUaCulSp Culex spChiSp Chironomidae spp (non-red type)ChiRe Chironomini spp (red-type)

Order Trichoptera

RhyNi Rhyacophila nigrocephala IwataHydKa Hydroptila KUaGloKa Glossosoma KUaCheBr Cheumatopsyche brevilineata IwataCheKa Cheumatopsyche KUaCheKb Cheumatopsyche KUbHydKo Hydropsyche kozhantschikovi MartynovHydKb Hydropsyche KUbHydOr Hydropsyche orientalis MartynovHydVa Hydropsyche valvata MartynovMacRa Macrostemum radiatum McLachlanPsySp Psychomyia sp

References

1 Dudgeon D Arthington AH Gessner MO Kawabata ZI Knowler DJ Leacutevecircque C Naiman RJPrieur-Richard AH Soto D Stiassny MLJ et al Freshwater biodiversity Importance threats status andconservation challenges Biol Rev 2006 81 163ndash182 [CrossRef] [PubMed]

2 Strayer DL Dudgeon D Freshwater biodiversity conservation Recent progress and future challengesJ N Am Benthol Soc 2010 29 344ndash358 [CrossRef]

3 Li F Chung N Bae M-J Kwon Y-S Park Y-S Relationships between stream macroinvertebrates andenvironmental variables at multiple spatial scales Freshwater Biol 2012 57 2107ndash2124 [CrossRef]

4 Dudgeon D The ecology of tropical Asian rivers and streams in relation to biodiversity conservationAnnu Rev Ecol Syst 2000 31 239ndash263 [CrossRef]

5 De Silva SS Abery NW Nguyen TTT Endemic freshwater finfish of Asia Distribution and conservationstatus Divers Distrib 2007 13 172ndash184 [CrossRef]

6 Voumlroumlsmarty CJ McIntyre PB Gessner MO Dudgeon D Prusevich A Green P Glidden S Bunn SESullivan CA Liermann CE et al Global threats to human water security and river biodiversity Nature2010 467 555ndash561 [CrossRef] [PubMed]

7 Strayer DL Challenges for freshwater invertebrate conservation J N Am Benthol Soc 2006 25 271ndash287[CrossRef]

8 Buss DF Baptista DF Silveira MP Nessimian JL Dorvilleacute LFM Influence of water chemistryand environmental degradation on macroinvertebrate assemblages in a river basin in south-east BrazilHydrobiologia 2002 481 125ndash136 [CrossRef]

9 Bott TL Brock JT Dunn CS Naiman RJ Ovink RW Petersen RC Benthic community metabolism infour temperate stream systems An inter-biome comparison and evaluation of the river continuum conceptHydrobiologia 1985 220 109ndash117 [CrossRef]

10 Merz JR Ochikubo Chan LK Effects of gravel augmentation on macroinvertebrate assemblages in aregulated California river River Res Appl 2005 21 61ndash74 [CrossRef]

11 Nelson SM Lieberman DM The influence of flow and other environmental factors on benthic invertebratesin the Sacramento River USA Hydrobiologia 2002 489 117ndash129 [CrossRef]

12 Jiang XM Xiong J Qiu JW Wu JM Wang JW Xie ZC Structure of macroinvertebrate communitiesin relation to environmental variables in a subtropical Asian river system Int Rev Hydrobiol 2010 95 42ndash57[CrossRef]

Water 2016 8 27 11 of 20

L gotoi indicating high trophy and saprobity [35] Water quality conditions in Group 2c (G2c) were aspoor as those of G2b with the highest EC Sites in this group were characterized with the lowest watervelocity and the largest proportion of fine particles because G2c was gathered by streams adjacent toestuaries large rivers and dammed streams The only three weak indicator species appeared in G2c

34 Environmental Variables Affecting Macroinvertebrate Distributions

A CCA was performed to understand how macroinvertebrates were distributed alongenvironmental gradients (Figure 4) Total variability explained in the species data was 159 (Table 4)The eigenvalues of the first CCA axis (0281) and the second CCA axis (0101) were significant (p lt 00199 Monte Carlo permutation test) All three CCA results were significant based on a Monte Carlopermutation test (p lt 001)

Figure 4 Ordination plots constructed by canonical correspondence analysis for all sampling sites(n = 720) The plots present the ordination of sampling sites (a) and macroinvertebrates (b) with relativecontributions of environmental variables (c) for the first two axes Only species contributing gt02to total abundance were included The summary of ordination results is presented in Table 4 and thecodes for each taxon are shown in Appendix Table A1

Water 2016 8 27 12 of 20

Table 4 Spearmanrsquos rank correlation coefficients and probabilities of environmental variables andthe CCA axes ( p lt 001 p lt 005) (a) and summary of CCA results (n = 720) (b) All axes weresignificant based on Monte Carlo permutation procedures

Variables Axis 1 Axis 2 Axis 3

(a) Correlation coefficients

Altitude 0793 0236 0013Stream order acute0105 acute0658 0099

Urban acute0218 0134 acute0317 Agriculture acute0199 acute0273 0133

Forest 0504 0055 0266 Water velocity 0662 acute0054 acute0510

Fine particles acute0744 0325 acute0076 Coarse particles 0747 acute0327 0075

pH 0011 acute0236 0007DO 0304 acute0467 acute0166

BOD acute0550 0164 acute0370 EC acute0196 acute0278 acute0116 TN acute0463 0266 acute0387 TP acute0373 0229 acute0314

(b) Summary of CCA results

Eigenvalue 0281 0101 0073 variance explained in

taxa data 98 35 25

Cumulative varianceexplained 98 133 159

p value 0010 0010 0010

Total variance 2869 - -

The five clusters were well separated in the CCA ordination plot (Figure 4a) Both the G1aand G1b groups with good physicochemical environments were positioned on the right side of theordination plot and G2b and G2c were on the opposite side However the G2a group straddledboth sides Eight environmental variables (ie BOD TN TP altitude water velocity forest fineparticles and coarse particles) had significant correlations with the first axis among which altitudewas the most significant contributor (r = 0793 p lt 001) followed by coarse particles (r = 0747p lt 001) and fine particles (r = acute0744 p lt 001) (Table 4) All physical factors except for fineparticles were in the opposite direction from the chemical variables (Figure 4c) This result suggeststhat the decline in altitude reflected deterioration in water quality accompanied by increases in organicmaterial and nutrients The heterogeneity of the macroinvertebrate habitats also decreased with thelongitudinal gradient toward downstream The second axis was negatively related with stream order(r =acute0658 p lt 001) and DO (r =acute0467 p lt 001) High positive scores with the first axis were denotedfor the rhithronic (ie pertaining to the headwaters) and intolerant species (eg Drunella aculea (Allen)E nipponicus Glossosoma sp R nigrocephala Iwata and H orientalis) whereas negative scores wereobserved for the potamic (ie pertaining to rivers) and tolerant taxa (eg Micronecta sedula HorvaacutethPhysa acuta Draparnaud Labiobaetis atrebatinus (Eaton) and Asellus hilgendorfii Bovalius) (Figure 4b)

4 Discussion

The Asian monsoon region is a global biodiversity hotspot suffering from increasinganthropogenic disturbances but aquatic biodiversity and ecosystem integrity remain poorlyexplored [3] This is the same situation in Korea but recent establishment of the National AquaticEcological Monitoring Program [36] opened a new era to assess ecosystem health and biodiversityin Korea Our work presented in this paper takes advantage of the opportunity of such anationwide scale of survey Although the five river watersheds in Korea exhibited differences in

Water 2016 8 27 13 of 20

environmental conditions and macroinvertebrate taxa abundance overall taxonomic compositionat each watershed displayed little difference (Table 2) Instead a considerable spatial variation inbenthic macroinvertebrate assemblages accounted for the combination of both ultimate (eg altitudeand the degree of land use) and proximate factors (eg flow stream bed substrate BOD EC andnutrients) This finding was in line with previous studies of benthic diatoms in Korea [25] andmacroinvertebrates in other Asian countries [1237] suggesting the importance of various multi-scalefactors in structuring macroinvertebrate assemblages [38] Our results provide basal information forthe sustainable management and conservation practices of stream ecosystems

41 Macroinvertebrate Taxonomic Composition

The macroinvertebrate assemblages in Korean stream ecosystems generally bear resemblance tothose in tropical and other temperate streams at higher taxonomic levels [3539] However temperateKorean streams were relatively rich in Ephemeroptera Diptera and Trichoptera when comparedwith tropical streams for the higher biodiversity of Gastropoda Decapoda and other insect orderssuch as Odonata and Hemiptera [3940] (Table 2) The taxonomic composition also included a largenumber of rhithronic fauna that prefer stony substrates For example Baetidae Heptageniidae andEphemerellidae mainly dominated the Ephemeroptera and Rhyacophilidae and Hydropsychidaecomposed the Trichoptera in this study

We confirmed a total of 340 macroinvertebrate taxa in this study Of the macroinvertebrate taxachironomid midge larvae and a small minnow mayfly (B fuscatus) were extensively encounteredthroughout Korean stream environments with the highest occurring frequency with 94 and 76of total sampling sites respectively Temperate Korean streams were also characterized with a fewpredominant colonizers and a majority of rare taxa in macroinvertebrate taxonomic compositionMoreover only six cosmopolitan taxa were noticeably comprised of gt60 of all macroinvertebratesamples which were L gotoi Chironomidae spp U punctisetae C brevilineata H valvata andH kozhantschikovi These dominant taxa were found to be significant indicators of mesotrophicor polytrophic streams in our study (Table 3) consistent with a result that most Korean streams andrivers were degraded in both chemical and biological status [36] On the other hand most Koreanstreams were occupied by a great number of rare macroinvertebrate species with a small distributionrange andor low abundance as was also demonstrated in other studies [4142]

42 Environmental Relationships with Macroinvertebrate Distribution

Benthic habitats are complex and a variety of environmental variables acting at multiple spatialscales regulate the composition and distribution patterns of stream macroinvertebrate assemblagesin an exclusive or synergistic fashion [3843] We revealed that the variables associated with altitudeand in-stream habitats best accounted for the largest amount of variability in our macroinvertebratedata set supporting the more important determinants of local environmental factors than broad orregional parameters [1644] The importance and role of local environmental variables have also beenhighlighted in other aquatic communities aquatic macrophytes [45] freshwater phytoplankton [46]benthic diatoms [44] intertidal macroinvertebrates [47] and fish [48] However a comprehensiveunderstanding of multispatial scales is needed because of significant correlations between macrohabitatand microhabitat characteristics depending on the relative size of the area studied [3]

In our study the variability among the macroinvertebrate-based stream groups was moreprominently explained by the altitudinal gradients together with streambed composition and watervelocity than chemical variables (Table 3) First the most widely accepted theory related to altitudinalchanges is the river continuum concept (RCC) which displays structural and functional responsesto the longitudinal gradient [49] Altitude has also been well documented in other studies as amain descriptor to determine macroinvertebrate richness as well as other environmental variablessuch as temperature hydrology food availability streambed condition and water chemistry [350]However we revealed poor relationships of altitude with water chemistry in contrast with significant

Water 2016 8 27 14 of 20

associations with physical variables and biological attributes such as taxa richness EPT richnessEPT abundance and the Shannon diversity index This may be due to the fact that over half ofthe studied streams corresponded to lowland streams below 100 m asl which were characterizedby moderate or slightly poor water quality with severe variations in BOD TN TP and Shannondiversity-based saprobity [3651] (Table 1) Harding et al [52] demonstrated that increasing humanland use intensity along a river continuum caused water quality degradation consequently leadingto changes in taxonomic composition from intolerant EPT dominated to tolerant taxa-dominatedassemblages despite a gradual increase in taxa abundance by a few dominant species

Riffle habitats are commonly characterized by shallow water depth oxygenating fast-flowingwater and stony beds and exhibit higher taxa richness and abundance than that at pools or habitatswith fine sediment as in our case [34253] Such hydraulic conditions are critical determinantsfor the distribution and species composition of benthic organisms [1654] and are the drivingforces for evolution of their morphologies and life history [11] Rheophilous (ie having an affinityfor running waters) and limnophilous taxa were clearly discriminated based on the correlationanalysis (Figure 2) and CCA (Figure 4) results For example well-known rhithronic species intwo Ephemeropteran (Ephemerellidae and Heptageniidae) and one Trichopteran (Hydropsychidae)families mostly displayed high preference to the mid- or fast current conditions which corresponds tothe intolerant scraper or filtering collector groups abundant in upper and middle stream reaches [49]Thus biological monitoring and assessment programs using rheophilic macroinvertebrates wouldbenefit from their ecological characteristics and their indication of good environmental quality(eg [42]) although seasonal fluctuations in hydraulic parameters by the Asian monsoon more criticallycause a catastrophic drift and washout of benthic organisms

Streambed composition is one of the most important factors to directly influence richness andabundance of macroinvertebrates on local scales [1216] thus close correlations would be expectedwith variables related to longitudinal changes in stream ecosystems Boulders and cobbles aretypically the major structural elements in steep gradient upper streams whereas sand and smallersediments predominate in the lower reaches [55] There have been a large number of studies onthe macroinvertebrate-substrate relationship most of which have revealed that macroinvertebratediversity and density increase with higher heterogeneity due to the available stable and diversemicrohabitats (eg [1043]) Therefore factors determining macroinvertebrate communities at localscales obviously put a priority on the streambed conditions rather than water quality or other physicalvariables We found that the mainstreams of the Nakdong River which contained about 60 fineparticles retained the lowest taxa richness (82 on average n = 18) and abundance (747 individualsm2)among five major rivers despite its good water quality condition (mean BOD 19 and TN 18 mgL)with the exception of the severely polluted Youngsan River (89 taxa richness and 73 BOD n = 13)These results indicate that homogeneous streambeds with greater fine particles support lower diversityand abundance even when streams maintain good water quality [56] Additionally organic pollutioncould transform the coarse substrate into an organic rich soft bottom altering the community structurefrom dominated by diverse and intolerant species to communities predominated by a few tolerantspecies [320] as in the case of the Youngsan River

43 Considerations to Improve Macroinvertebrate Biomonitoring Programs

Not until 2006 did Korea adopt biological water quality criteria and the concept of ecologicalintegrity in the water quality program [2536] Since then Korean government has led a biologicalsurvey of streams and rivers (ie NAEMP) every year to assess the current biological status of streamand river ecosystems and to develop a strategy for the restoration and management of disturbedsystems [25] As a part of a nationwide survey benthic macroinvertebrates are also monitored based onthe guidelines and assessment tools [27] Notwithstanding their suitability for convenient and rapidbio-assessment there remain debatable issues as to whether the methods for sampling and treating

Water 2016 8 27 15 of 20

macroinvertebrates are effective to provide a reliable and accurate indication of the macroinvertebratefauna throughout the country

The Korean national biomonitoring program presents field sampling in a cost-effective andtime-saving manner for rapid bio-assessment To satisfy this purpose benthic macroinvertebratesare optimized to be collected at riffle andor gliding run habitats using a Surber sampler with threereplicates [27] However such sampling methods probably underestimate overall biodiversity instream ecosystems considering the whole stream environment First single-habitat sampling possiblyproduces incomplete taxa lists and includes no target habitats at certain sites despite its advantagethat the influences of both water and habitat quality on macroinvertebrates are not confounded byinstream habitat variation [57] In this regard a multihabitat approach would be more profitablefor the estimation of taxonomic diversity due to its consistent application across stream typesespecially at large-scaled survey comprehensive taxa lists and effective assessment of ecologicalconditions [58] Second the Surber sampler is one of the most commonly used quantitative toolsin lotic systems and provides high-precision information on the abundance and composition ofmacroinvertebrate assemblages [2159] This method is on the other hand usually more appropriatefor riffle habitats of shallow streams presumably underestimating overall biodiversity in a regionRecent studies on the comparison between sampling devices suggested that artificial substrates(eg leaf-bags) would be used as complementary tools due to their discriminative taxonomiccomposition [60ndash62] Third a majority of biomonitoring programs widely adopt three to five replicatesfor lotic ecosystems because one way to reduce monitoring costs is to decrease the sample size [216364]The previous studies also showed that such a small number of replicates rarely influenced ecologicalhealth assessment particularly for the indices applying sensitivitytolerance taxa as the same forNAEMP [65ndash67] Nevertheless small sample sizes may influence the values of biological measuresand the representativeness for a real benthic community based on the asymptotic relationship ofthe number of taxa with both the sampling area and the collected individuals [68] Finally sievemesh size could also affect the accurate estimates of taxonomic diversity and environmental qualityassessment [67] Finer mesh sizes more accurately represent macroinvertebrate assemblages thancoarser mesh sizes whereas they need more efforts to handle specimens On the contrary coarsermesh sizes undervalue the original density and taxa richness of macroinvertebrate assemblages bypassing small individuals through the sieves and result in higher diversity [69] Considering thetradeoff between cost and effectiveness many rapid bio-assessments determine 05 mm mesh size as areasonable choice [216470] Therefore future researches are required for identifying optimal samplingeffort comprehensively considering cost-effectiveness easy applicability and well representative ofresident macroinvertebrate assemblages

5 Conclusions

Large-scale knowledge on environmental relationships of aquatic communities is crucial toconserve freshwater biodiversity and sustain ecological integrity Korean stream macroinvertebrateassemblages were determined not only by regional and physical instream variables but also bypollution-related parameters at nation-wide scale Macroinvertebrate-based site classification evidentlyprovided an environmental characterization for different types of Korean streams indicating thatbenthic macroinvertebrates are a valuable biomonitoring material The results of this study provideimportant information and a bridge for further work such as the assemblagemdashspecific responses toenvironmental disturbance Our results also contribute to establishing effective management practicesimplementing conservation measures and developing more reliable biological monitoring tools forsustainable freshwater ecosystems

Acknowledgments This study was performed under the project of ldquoNational Aquatic Ecosystem Health Surveyand Assessmentrdquo in Korea and was supported by the Ministry of Environment and the National Institute ofEnvironmental Research Korea The authors are grateful to survey members involved in the project The authorsalso thank the anonymous reviewers for their help in improving the scientific content of the manuscript

Water 2016 8 27 16 of 20

Author Contributions Yung-Chul Jun developed the concept of the study performed data analysis and wrotethe manuscript Nan-Young Kim assisted data processing and figure construction Sang-Hun Kim conductedquality assurance of the physico-chemical and biological data Young-Seuk Park and Dong-Soo Kong assistedstudy design and statistical analysis Soon-Jin Hwang supervised the research and assisted data interpretationand manuscript preparation All the authors contributed to the review of the manuscript

Conflicts of Interest The authors declare no conflict of interest

Appendix A

Table A1 Codes for macroinvertebrates contributing to more than 02 of total abundance for canonicalcorrespondence analysis in Figure 4

Code TaxonPhylum Platyhelminthes

DugSp Dugesia spPhylum Mollusca

SemLi Semisulcospira libertina (Gould)PhyAc Physa acuta Draparnaud

Phylum AnnelidaLimGo Limnodrilus gotoi HataiHirNi Hirudo nipponia Whitman

Phylum ArthropodaClass Crustacea

AseSp Asellus spGamSp Gammarus sp

Class Insecta

Order Ephemeroptera

BaeTu Baetiella tuberculata (Kazlauskas)BaeFu Baetis fuscatus (Linnaeus)BaeUr Baetis ursinus KazlauskasLabAt Labiobaetis atrebatinus (Eaton)NigBa Nigrobaetis bacillus (Kluge)EcdBa Ecdyonurus bajkovae KlugeEcdJo Ecdyonurus joernensis BengtssonEcdKi Ecdyonurus kibunensis ImanishiEcdLe Ecdyonurus levis (Navaacutes)EpeNi Epeorus nipponicus (Ueacuteno)EpeLa Epeorus latifolium (Ueacuteno)EpePe Epeorus pellucidus (Brodsky)ChoAl Choroterpes altioculus KlugeParJa Paraleptophlebia japonica (Matsumura)PotFo Potamanthus formosus EatonRhoCo Rhoenanthus coreanus (Yoon and Bae)DruAc Drunella aculea (Allen)EphOr Ephemera orientalis McLachlanSerSe Serratella setigera (Bajkova)UraPu Uracanthella punctisetae (Matsumura)CaeNi Caenis nishinoae Malzacher

Order Hemiptera

MicSe Micronecta sedula HorvaacutethMicSp Micronecta sp

Order Coleoptera

ElmSp Elmidae spEubKa Eubrianax KUaMatKa Mataeopsephus KUaPseKa Psephenoides KUa

Water 2016 8 27 17 of 20

Table A1 Cont

Code Taxon

Order Diptera

AntKa Antocha KUaCulSp Culex spChiSp Chironomidae spp (non-red type)ChiRe Chironomini spp (red-type)

Order Trichoptera

RhyNi Rhyacophila nigrocephala IwataHydKa Hydroptila KUaGloKa Glossosoma KUaCheBr Cheumatopsyche brevilineata IwataCheKa Cheumatopsyche KUaCheKb Cheumatopsyche KUbHydKo Hydropsyche kozhantschikovi MartynovHydKb Hydropsyche KUbHydOr Hydropsyche orientalis MartynovHydVa Hydropsyche valvata MartynovMacRa Macrostemum radiatum McLachlanPsySp Psychomyia sp

References

1 Dudgeon D Arthington AH Gessner MO Kawabata ZI Knowler DJ Leacutevecircque C Naiman RJPrieur-Richard AH Soto D Stiassny MLJ et al Freshwater biodiversity Importance threats status andconservation challenges Biol Rev 2006 81 163ndash182 [CrossRef] [PubMed]

2 Strayer DL Dudgeon D Freshwater biodiversity conservation Recent progress and future challengesJ N Am Benthol Soc 2010 29 344ndash358 [CrossRef]

3 Li F Chung N Bae M-J Kwon Y-S Park Y-S Relationships between stream macroinvertebrates andenvironmental variables at multiple spatial scales Freshwater Biol 2012 57 2107ndash2124 [CrossRef]

4 Dudgeon D The ecology of tropical Asian rivers and streams in relation to biodiversity conservationAnnu Rev Ecol Syst 2000 31 239ndash263 [CrossRef]

5 De Silva SS Abery NW Nguyen TTT Endemic freshwater finfish of Asia Distribution and conservationstatus Divers Distrib 2007 13 172ndash184 [CrossRef]

6 Voumlroumlsmarty CJ McIntyre PB Gessner MO Dudgeon D Prusevich A Green P Glidden S Bunn SESullivan CA Liermann CE et al Global threats to human water security and river biodiversity Nature2010 467 555ndash561 [CrossRef] [PubMed]

7 Strayer DL Challenges for freshwater invertebrate conservation J N Am Benthol Soc 2006 25 271ndash287[CrossRef]

8 Buss DF Baptista DF Silveira MP Nessimian JL Dorvilleacute LFM Influence of water chemistryand environmental degradation on macroinvertebrate assemblages in a river basin in south-east BrazilHydrobiologia 2002 481 125ndash136 [CrossRef]

9 Bott TL Brock JT Dunn CS Naiman RJ Ovink RW Petersen RC Benthic community metabolism infour temperate stream systems An inter-biome comparison and evaluation of the river continuum conceptHydrobiologia 1985 220 109ndash117 [CrossRef]

10 Merz JR Ochikubo Chan LK Effects of gravel augmentation on macroinvertebrate assemblages in aregulated California river River Res Appl 2005 21 61ndash74 [CrossRef]

11 Nelson SM Lieberman DM The influence of flow and other environmental factors on benthic invertebratesin the Sacramento River USA Hydrobiologia 2002 489 117ndash129 [CrossRef]

12 Jiang XM Xiong J Qiu JW Wu JM Wang JW Xie ZC Structure of macroinvertebrate communitiesin relation to environmental variables in a subtropical Asian river system Int Rev Hydrobiol 2010 95 42ndash57[CrossRef]

Water 2016 8 27 12 of 20

Table 4 Spearmanrsquos rank correlation coefficients and probabilities of environmental variables andthe CCA axes ( p lt 001 p lt 005) (a) and summary of CCA results (n = 720) (b) All axes weresignificant based on Monte Carlo permutation procedures

Variables Axis 1 Axis 2 Axis 3

(a) Correlation coefficients

Altitude 0793 0236 0013Stream order acute0105 acute0658 0099

Urban acute0218 0134 acute0317 Agriculture acute0199 acute0273 0133

Forest 0504 0055 0266 Water velocity 0662 acute0054 acute0510

Fine particles acute0744 0325 acute0076 Coarse particles 0747 acute0327 0075

pH 0011 acute0236 0007DO 0304 acute0467 acute0166

BOD acute0550 0164 acute0370 EC acute0196 acute0278 acute0116 TN acute0463 0266 acute0387 TP acute0373 0229 acute0314

(b) Summary of CCA results

Eigenvalue 0281 0101 0073 variance explained in

taxa data 98 35 25

Cumulative varianceexplained 98 133 159

p value 0010 0010 0010

Total variance 2869 - -

The five clusters were well separated in the CCA ordination plot (Figure 4a) Both the G1aand G1b groups with good physicochemical environments were positioned on the right side of theordination plot and G2b and G2c were on the opposite side However the G2a group straddledboth sides Eight environmental variables (ie BOD TN TP altitude water velocity forest fineparticles and coarse particles) had significant correlations with the first axis among which altitudewas the most significant contributor (r = 0793 p lt 001) followed by coarse particles (r = 0747p lt 001) and fine particles (r = acute0744 p lt 001) (Table 4) All physical factors except for fineparticles were in the opposite direction from the chemical variables (Figure 4c) This result suggeststhat the decline in altitude reflected deterioration in water quality accompanied by increases in organicmaterial and nutrients The heterogeneity of the macroinvertebrate habitats also decreased with thelongitudinal gradient toward downstream The second axis was negatively related with stream order(r =acute0658 p lt 001) and DO (r =acute0467 p lt 001) High positive scores with the first axis were denotedfor the rhithronic (ie pertaining to the headwaters) and intolerant species (eg Drunella aculea (Allen)E nipponicus Glossosoma sp R nigrocephala Iwata and H orientalis) whereas negative scores wereobserved for the potamic (ie pertaining to rivers) and tolerant taxa (eg Micronecta sedula HorvaacutethPhysa acuta Draparnaud Labiobaetis atrebatinus (Eaton) and Asellus hilgendorfii Bovalius) (Figure 4b)

4 Discussion

The Asian monsoon region is a global biodiversity hotspot suffering from increasinganthropogenic disturbances but aquatic biodiversity and ecosystem integrity remain poorlyexplored [3] This is the same situation in Korea but recent establishment of the National AquaticEcological Monitoring Program [36] opened a new era to assess ecosystem health and biodiversityin Korea Our work presented in this paper takes advantage of the opportunity of such anationwide scale of survey Although the five river watersheds in Korea exhibited differences in

Water 2016 8 27 13 of 20

environmental conditions and macroinvertebrate taxa abundance overall taxonomic compositionat each watershed displayed little difference (Table 2) Instead a considerable spatial variation inbenthic macroinvertebrate assemblages accounted for the combination of both ultimate (eg altitudeand the degree of land use) and proximate factors (eg flow stream bed substrate BOD EC andnutrients) This finding was in line with previous studies of benthic diatoms in Korea [25] andmacroinvertebrates in other Asian countries [1237] suggesting the importance of various multi-scalefactors in structuring macroinvertebrate assemblages [38] Our results provide basal information forthe sustainable management and conservation practices of stream ecosystems

41 Macroinvertebrate Taxonomic Composition

The macroinvertebrate assemblages in Korean stream ecosystems generally bear resemblance tothose in tropical and other temperate streams at higher taxonomic levels [3539] However temperateKorean streams were relatively rich in Ephemeroptera Diptera and Trichoptera when comparedwith tropical streams for the higher biodiversity of Gastropoda Decapoda and other insect orderssuch as Odonata and Hemiptera [3940] (Table 2) The taxonomic composition also included a largenumber of rhithronic fauna that prefer stony substrates For example Baetidae Heptageniidae andEphemerellidae mainly dominated the Ephemeroptera and Rhyacophilidae and Hydropsychidaecomposed the Trichoptera in this study

We confirmed a total of 340 macroinvertebrate taxa in this study Of the macroinvertebrate taxachironomid midge larvae and a small minnow mayfly (B fuscatus) were extensively encounteredthroughout Korean stream environments with the highest occurring frequency with 94 and 76of total sampling sites respectively Temperate Korean streams were also characterized with a fewpredominant colonizers and a majority of rare taxa in macroinvertebrate taxonomic compositionMoreover only six cosmopolitan taxa were noticeably comprised of gt60 of all macroinvertebratesamples which were L gotoi Chironomidae spp U punctisetae C brevilineata H valvata andH kozhantschikovi These dominant taxa were found to be significant indicators of mesotrophicor polytrophic streams in our study (Table 3) consistent with a result that most Korean streams andrivers were degraded in both chemical and biological status [36] On the other hand most Koreanstreams were occupied by a great number of rare macroinvertebrate species with a small distributionrange andor low abundance as was also demonstrated in other studies [4142]

42 Environmental Relationships with Macroinvertebrate Distribution

Benthic habitats are complex and a variety of environmental variables acting at multiple spatialscales regulate the composition and distribution patterns of stream macroinvertebrate assemblagesin an exclusive or synergistic fashion [3843] We revealed that the variables associated with altitudeand in-stream habitats best accounted for the largest amount of variability in our macroinvertebratedata set supporting the more important determinants of local environmental factors than broad orregional parameters [1644] The importance and role of local environmental variables have also beenhighlighted in other aquatic communities aquatic macrophytes [45] freshwater phytoplankton [46]benthic diatoms [44] intertidal macroinvertebrates [47] and fish [48] However a comprehensiveunderstanding of multispatial scales is needed because of significant correlations between macrohabitatand microhabitat characteristics depending on the relative size of the area studied [3]

In our study the variability among the macroinvertebrate-based stream groups was moreprominently explained by the altitudinal gradients together with streambed composition and watervelocity than chemical variables (Table 3) First the most widely accepted theory related to altitudinalchanges is the river continuum concept (RCC) which displays structural and functional responsesto the longitudinal gradient [49] Altitude has also been well documented in other studies as amain descriptor to determine macroinvertebrate richness as well as other environmental variablessuch as temperature hydrology food availability streambed condition and water chemistry [350]However we revealed poor relationships of altitude with water chemistry in contrast with significant

Water 2016 8 27 14 of 20

associations with physical variables and biological attributes such as taxa richness EPT richnessEPT abundance and the Shannon diversity index This may be due to the fact that over half ofthe studied streams corresponded to lowland streams below 100 m asl which were characterizedby moderate or slightly poor water quality with severe variations in BOD TN TP and Shannondiversity-based saprobity [3651] (Table 1) Harding et al [52] demonstrated that increasing humanland use intensity along a river continuum caused water quality degradation consequently leadingto changes in taxonomic composition from intolerant EPT dominated to tolerant taxa-dominatedassemblages despite a gradual increase in taxa abundance by a few dominant species

Riffle habitats are commonly characterized by shallow water depth oxygenating fast-flowingwater and stony beds and exhibit higher taxa richness and abundance than that at pools or habitatswith fine sediment as in our case [34253] Such hydraulic conditions are critical determinantsfor the distribution and species composition of benthic organisms [1654] and are the drivingforces for evolution of their morphologies and life history [11] Rheophilous (ie having an affinityfor running waters) and limnophilous taxa were clearly discriminated based on the correlationanalysis (Figure 2) and CCA (Figure 4) results For example well-known rhithronic species intwo Ephemeropteran (Ephemerellidae and Heptageniidae) and one Trichopteran (Hydropsychidae)families mostly displayed high preference to the mid- or fast current conditions which corresponds tothe intolerant scraper or filtering collector groups abundant in upper and middle stream reaches [49]Thus biological monitoring and assessment programs using rheophilic macroinvertebrates wouldbenefit from their ecological characteristics and their indication of good environmental quality(eg [42]) although seasonal fluctuations in hydraulic parameters by the Asian monsoon more criticallycause a catastrophic drift and washout of benthic organisms

Streambed composition is one of the most important factors to directly influence richness andabundance of macroinvertebrates on local scales [1216] thus close correlations would be expectedwith variables related to longitudinal changes in stream ecosystems Boulders and cobbles aretypically the major structural elements in steep gradient upper streams whereas sand and smallersediments predominate in the lower reaches [55] There have been a large number of studies onthe macroinvertebrate-substrate relationship most of which have revealed that macroinvertebratediversity and density increase with higher heterogeneity due to the available stable and diversemicrohabitats (eg [1043]) Therefore factors determining macroinvertebrate communities at localscales obviously put a priority on the streambed conditions rather than water quality or other physicalvariables We found that the mainstreams of the Nakdong River which contained about 60 fineparticles retained the lowest taxa richness (82 on average n = 18) and abundance (747 individualsm2)among five major rivers despite its good water quality condition (mean BOD 19 and TN 18 mgL)with the exception of the severely polluted Youngsan River (89 taxa richness and 73 BOD n = 13)These results indicate that homogeneous streambeds with greater fine particles support lower diversityand abundance even when streams maintain good water quality [56] Additionally organic pollutioncould transform the coarse substrate into an organic rich soft bottom altering the community structurefrom dominated by diverse and intolerant species to communities predominated by a few tolerantspecies [320] as in the case of the Youngsan River

43 Considerations to Improve Macroinvertebrate Biomonitoring Programs

Not until 2006 did Korea adopt biological water quality criteria and the concept of ecologicalintegrity in the water quality program [2536] Since then Korean government has led a biologicalsurvey of streams and rivers (ie NAEMP) every year to assess the current biological status of streamand river ecosystems and to develop a strategy for the restoration and management of disturbedsystems [25] As a part of a nationwide survey benthic macroinvertebrates are also monitored based onthe guidelines and assessment tools [27] Notwithstanding their suitability for convenient and rapidbio-assessment there remain debatable issues as to whether the methods for sampling and treating

Water 2016 8 27 15 of 20

macroinvertebrates are effective to provide a reliable and accurate indication of the macroinvertebratefauna throughout the country

The Korean national biomonitoring program presents field sampling in a cost-effective andtime-saving manner for rapid bio-assessment To satisfy this purpose benthic macroinvertebratesare optimized to be collected at riffle andor gliding run habitats using a Surber sampler with threereplicates [27] However such sampling methods probably underestimate overall biodiversity instream ecosystems considering the whole stream environment First single-habitat sampling possiblyproduces incomplete taxa lists and includes no target habitats at certain sites despite its advantagethat the influences of both water and habitat quality on macroinvertebrates are not confounded byinstream habitat variation [57] In this regard a multihabitat approach would be more profitablefor the estimation of taxonomic diversity due to its consistent application across stream typesespecially at large-scaled survey comprehensive taxa lists and effective assessment of ecologicalconditions [58] Second the Surber sampler is one of the most commonly used quantitative toolsin lotic systems and provides high-precision information on the abundance and composition ofmacroinvertebrate assemblages [2159] This method is on the other hand usually more appropriatefor riffle habitats of shallow streams presumably underestimating overall biodiversity in a regionRecent studies on the comparison between sampling devices suggested that artificial substrates(eg leaf-bags) would be used as complementary tools due to their discriminative taxonomiccomposition [60ndash62] Third a majority of biomonitoring programs widely adopt three to five replicatesfor lotic ecosystems because one way to reduce monitoring costs is to decrease the sample size [216364]The previous studies also showed that such a small number of replicates rarely influenced ecologicalhealth assessment particularly for the indices applying sensitivitytolerance taxa as the same forNAEMP [65ndash67] Nevertheless small sample sizes may influence the values of biological measuresand the representativeness for a real benthic community based on the asymptotic relationship ofthe number of taxa with both the sampling area and the collected individuals [68] Finally sievemesh size could also affect the accurate estimates of taxonomic diversity and environmental qualityassessment [67] Finer mesh sizes more accurately represent macroinvertebrate assemblages thancoarser mesh sizes whereas they need more efforts to handle specimens On the contrary coarsermesh sizes undervalue the original density and taxa richness of macroinvertebrate assemblages bypassing small individuals through the sieves and result in higher diversity [69] Considering thetradeoff between cost and effectiveness many rapid bio-assessments determine 05 mm mesh size as areasonable choice [216470] Therefore future researches are required for identifying optimal samplingeffort comprehensively considering cost-effectiveness easy applicability and well representative ofresident macroinvertebrate assemblages

5 Conclusions

Large-scale knowledge on environmental relationships of aquatic communities is crucial toconserve freshwater biodiversity and sustain ecological integrity Korean stream macroinvertebrateassemblages were determined not only by regional and physical instream variables but also bypollution-related parameters at nation-wide scale Macroinvertebrate-based site classification evidentlyprovided an environmental characterization for different types of Korean streams indicating thatbenthic macroinvertebrates are a valuable biomonitoring material The results of this study provideimportant information and a bridge for further work such as the assemblagemdashspecific responses toenvironmental disturbance Our results also contribute to establishing effective management practicesimplementing conservation measures and developing more reliable biological monitoring tools forsustainable freshwater ecosystems

Acknowledgments This study was performed under the project of ldquoNational Aquatic Ecosystem Health Surveyand Assessmentrdquo in Korea and was supported by the Ministry of Environment and the National Institute ofEnvironmental Research Korea The authors are grateful to survey members involved in the project The authorsalso thank the anonymous reviewers for their help in improving the scientific content of the manuscript

Water 2016 8 27 16 of 20

Author Contributions Yung-Chul Jun developed the concept of the study performed data analysis and wrotethe manuscript Nan-Young Kim assisted data processing and figure construction Sang-Hun Kim conductedquality assurance of the physico-chemical and biological data Young-Seuk Park and Dong-Soo Kong assistedstudy design and statistical analysis Soon-Jin Hwang supervised the research and assisted data interpretationand manuscript preparation All the authors contributed to the review of the manuscript

Conflicts of Interest The authors declare no conflict of interest

Appendix A

Table A1 Codes for macroinvertebrates contributing to more than 02 of total abundance for canonicalcorrespondence analysis in Figure 4

Code TaxonPhylum Platyhelminthes

DugSp Dugesia spPhylum Mollusca

SemLi Semisulcospira libertina (Gould)PhyAc Physa acuta Draparnaud

Phylum AnnelidaLimGo Limnodrilus gotoi HataiHirNi Hirudo nipponia Whitman

Phylum ArthropodaClass Crustacea

AseSp Asellus spGamSp Gammarus sp

Class Insecta

Order Ephemeroptera

BaeTu Baetiella tuberculata (Kazlauskas)BaeFu Baetis fuscatus (Linnaeus)BaeUr Baetis ursinus KazlauskasLabAt Labiobaetis atrebatinus (Eaton)NigBa Nigrobaetis bacillus (Kluge)EcdBa Ecdyonurus bajkovae KlugeEcdJo Ecdyonurus joernensis BengtssonEcdKi Ecdyonurus kibunensis ImanishiEcdLe Ecdyonurus levis (Navaacutes)EpeNi Epeorus nipponicus (Ueacuteno)EpeLa Epeorus latifolium (Ueacuteno)EpePe Epeorus pellucidus (Brodsky)ChoAl Choroterpes altioculus KlugeParJa Paraleptophlebia japonica (Matsumura)PotFo Potamanthus formosus EatonRhoCo Rhoenanthus coreanus (Yoon and Bae)DruAc Drunella aculea (Allen)EphOr Ephemera orientalis McLachlanSerSe Serratella setigera (Bajkova)UraPu Uracanthella punctisetae (Matsumura)CaeNi Caenis nishinoae Malzacher

Order Hemiptera

MicSe Micronecta sedula HorvaacutethMicSp Micronecta sp

Order Coleoptera

ElmSp Elmidae spEubKa Eubrianax KUaMatKa Mataeopsephus KUaPseKa Psephenoides KUa

Water 2016 8 27 17 of 20

Table A1 Cont

Code Taxon

Order Diptera

AntKa Antocha KUaCulSp Culex spChiSp Chironomidae spp (non-red type)ChiRe Chironomini spp (red-type)

Order Trichoptera

RhyNi Rhyacophila nigrocephala IwataHydKa Hydroptila KUaGloKa Glossosoma KUaCheBr Cheumatopsyche brevilineata IwataCheKa Cheumatopsyche KUaCheKb Cheumatopsyche KUbHydKo Hydropsyche kozhantschikovi MartynovHydKb Hydropsyche KUbHydOr Hydropsyche orientalis MartynovHydVa Hydropsyche valvata MartynovMacRa Macrostemum radiatum McLachlanPsySp Psychomyia sp

References

1 Dudgeon D Arthington AH Gessner MO Kawabata ZI Knowler DJ Leacutevecircque C Naiman RJPrieur-Richard AH Soto D Stiassny MLJ et al Freshwater biodiversity Importance threats status andconservation challenges Biol Rev 2006 81 163ndash182 [CrossRef] [PubMed]

2 Strayer DL Dudgeon D Freshwater biodiversity conservation Recent progress and future challengesJ N Am Benthol Soc 2010 29 344ndash358 [CrossRef]

3 Li F Chung N Bae M-J Kwon Y-S Park Y-S Relationships between stream macroinvertebrates andenvironmental variables at multiple spatial scales Freshwater Biol 2012 57 2107ndash2124 [CrossRef]

4 Dudgeon D The ecology of tropical Asian rivers and streams in relation to biodiversity conservationAnnu Rev Ecol Syst 2000 31 239ndash263 [CrossRef]

5 De Silva SS Abery NW Nguyen TTT Endemic freshwater finfish of Asia Distribution and conservationstatus Divers Distrib 2007 13 172ndash184 [CrossRef]

6 Voumlroumlsmarty CJ McIntyre PB Gessner MO Dudgeon D Prusevich A Green P Glidden S Bunn SESullivan CA Liermann CE et al Global threats to human water security and river biodiversity Nature2010 467 555ndash561 [CrossRef] [PubMed]

7 Strayer DL Challenges for freshwater invertebrate conservation J N Am Benthol Soc 2006 25 271ndash287[CrossRef]

8 Buss DF Baptista DF Silveira MP Nessimian JL Dorvilleacute LFM Influence of water chemistryand environmental degradation on macroinvertebrate assemblages in a river basin in south-east BrazilHydrobiologia 2002 481 125ndash136 [CrossRef]

9 Bott TL Brock JT Dunn CS Naiman RJ Ovink RW Petersen RC Benthic community metabolism infour temperate stream systems An inter-biome comparison and evaluation of the river continuum conceptHydrobiologia 1985 220 109ndash117 [CrossRef]

10 Merz JR Ochikubo Chan LK Effects of gravel augmentation on macroinvertebrate assemblages in aregulated California river River Res Appl 2005 21 61ndash74 [CrossRef]

11 Nelson SM Lieberman DM The influence of flow and other environmental factors on benthic invertebratesin the Sacramento River USA Hydrobiologia 2002 489 117ndash129 [CrossRef]

12 Jiang XM Xiong J Qiu JW Wu JM Wang JW Xie ZC Structure of macroinvertebrate communitiesin relation to environmental variables in a subtropical Asian river system Int Rev Hydrobiol 2010 95 42ndash57[CrossRef]

Water 2016 8 27 13 of 20

environmental conditions and macroinvertebrate taxa abundance overall taxonomic compositionat each watershed displayed little difference (Table 2) Instead a considerable spatial variation inbenthic macroinvertebrate assemblages accounted for the combination of both ultimate (eg altitudeand the degree of land use) and proximate factors (eg flow stream bed substrate BOD EC andnutrients) This finding was in line with previous studies of benthic diatoms in Korea [25] andmacroinvertebrates in other Asian countries [1237] suggesting the importance of various multi-scalefactors in structuring macroinvertebrate assemblages [38] Our results provide basal information forthe sustainable management and conservation practices of stream ecosystems

41 Macroinvertebrate Taxonomic Composition

The macroinvertebrate assemblages in Korean stream ecosystems generally bear resemblance tothose in tropical and other temperate streams at higher taxonomic levels [3539] However temperateKorean streams were relatively rich in Ephemeroptera Diptera and Trichoptera when comparedwith tropical streams for the higher biodiversity of Gastropoda Decapoda and other insect orderssuch as Odonata and Hemiptera [3940] (Table 2) The taxonomic composition also included a largenumber of rhithronic fauna that prefer stony substrates For example Baetidae Heptageniidae andEphemerellidae mainly dominated the Ephemeroptera and Rhyacophilidae and Hydropsychidaecomposed the Trichoptera in this study

We confirmed a total of 340 macroinvertebrate taxa in this study Of the macroinvertebrate taxachironomid midge larvae and a small minnow mayfly (B fuscatus) were extensively encounteredthroughout Korean stream environments with the highest occurring frequency with 94 and 76of total sampling sites respectively Temperate Korean streams were also characterized with a fewpredominant colonizers and a majority of rare taxa in macroinvertebrate taxonomic compositionMoreover only six cosmopolitan taxa were noticeably comprised of gt60 of all macroinvertebratesamples which were L gotoi Chironomidae spp U punctisetae C brevilineata H valvata andH kozhantschikovi These dominant taxa were found to be significant indicators of mesotrophicor polytrophic streams in our study (Table 3) consistent with a result that most Korean streams andrivers were degraded in both chemical and biological status [36] On the other hand most Koreanstreams were occupied by a great number of rare macroinvertebrate species with a small distributionrange andor low abundance as was also demonstrated in other studies [4142]

42 Environmental Relationships with Macroinvertebrate Distribution

Benthic habitats are complex and a variety of environmental variables acting at multiple spatialscales regulate the composition and distribution patterns of stream macroinvertebrate assemblagesin an exclusive or synergistic fashion [3843] We revealed that the variables associated with altitudeand in-stream habitats best accounted for the largest amount of variability in our macroinvertebratedata set supporting the more important determinants of local environmental factors than broad orregional parameters [1644] The importance and role of local environmental variables have also beenhighlighted in other aquatic communities aquatic macrophytes [45] freshwater phytoplankton [46]benthic diatoms [44] intertidal macroinvertebrates [47] and fish [48] However a comprehensiveunderstanding of multispatial scales is needed because of significant correlations between macrohabitatand microhabitat characteristics depending on the relative size of the area studied [3]

In our study the variability among the macroinvertebrate-based stream groups was moreprominently explained by the altitudinal gradients together with streambed composition and watervelocity than chemical variables (Table 3) First the most widely accepted theory related to altitudinalchanges is the river continuum concept (RCC) which displays structural and functional responsesto the longitudinal gradient [49] Altitude has also been well documented in other studies as amain descriptor to determine macroinvertebrate richness as well as other environmental variablessuch as temperature hydrology food availability streambed condition and water chemistry [350]However we revealed poor relationships of altitude with water chemistry in contrast with significant

Water 2016 8 27 14 of 20

associations with physical variables and biological attributes such as taxa richness EPT richnessEPT abundance and the Shannon diversity index This may be due to the fact that over half ofthe studied streams corresponded to lowland streams below 100 m asl which were characterizedby moderate or slightly poor water quality with severe variations in BOD TN TP and Shannondiversity-based saprobity [3651] (Table 1) Harding et al [52] demonstrated that increasing humanland use intensity along a river continuum caused water quality degradation consequently leadingto changes in taxonomic composition from intolerant EPT dominated to tolerant taxa-dominatedassemblages despite a gradual increase in taxa abundance by a few dominant species

Riffle habitats are commonly characterized by shallow water depth oxygenating fast-flowingwater and stony beds and exhibit higher taxa richness and abundance than that at pools or habitatswith fine sediment as in our case [34253] Such hydraulic conditions are critical determinantsfor the distribution and species composition of benthic organisms [1654] and are the drivingforces for evolution of their morphologies and life history [11] Rheophilous (ie having an affinityfor running waters) and limnophilous taxa were clearly discriminated based on the correlationanalysis (Figure 2) and CCA (Figure 4) results For example well-known rhithronic species intwo Ephemeropteran (Ephemerellidae and Heptageniidae) and one Trichopteran (Hydropsychidae)families mostly displayed high preference to the mid- or fast current conditions which corresponds tothe intolerant scraper or filtering collector groups abundant in upper and middle stream reaches [49]Thus biological monitoring and assessment programs using rheophilic macroinvertebrates wouldbenefit from their ecological characteristics and their indication of good environmental quality(eg [42]) although seasonal fluctuations in hydraulic parameters by the Asian monsoon more criticallycause a catastrophic drift and washout of benthic organisms

Streambed composition is one of the most important factors to directly influence richness andabundance of macroinvertebrates on local scales [1216] thus close correlations would be expectedwith variables related to longitudinal changes in stream ecosystems Boulders and cobbles aretypically the major structural elements in steep gradient upper streams whereas sand and smallersediments predominate in the lower reaches [55] There have been a large number of studies onthe macroinvertebrate-substrate relationship most of which have revealed that macroinvertebratediversity and density increase with higher heterogeneity due to the available stable and diversemicrohabitats (eg [1043]) Therefore factors determining macroinvertebrate communities at localscales obviously put a priority on the streambed conditions rather than water quality or other physicalvariables We found that the mainstreams of the Nakdong River which contained about 60 fineparticles retained the lowest taxa richness (82 on average n = 18) and abundance (747 individualsm2)among five major rivers despite its good water quality condition (mean BOD 19 and TN 18 mgL)with the exception of the severely polluted Youngsan River (89 taxa richness and 73 BOD n = 13)These results indicate that homogeneous streambeds with greater fine particles support lower diversityand abundance even when streams maintain good water quality [56] Additionally organic pollutioncould transform the coarse substrate into an organic rich soft bottom altering the community structurefrom dominated by diverse and intolerant species to communities predominated by a few tolerantspecies [320] as in the case of the Youngsan River

43 Considerations to Improve Macroinvertebrate Biomonitoring Programs

Not until 2006 did Korea adopt biological water quality criteria and the concept of ecologicalintegrity in the water quality program [2536] Since then Korean government has led a biologicalsurvey of streams and rivers (ie NAEMP) every year to assess the current biological status of streamand river ecosystems and to develop a strategy for the restoration and management of disturbedsystems [25] As a part of a nationwide survey benthic macroinvertebrates are also monitored based onthe guidelines and assessment tools [27] Notwithstanding their suitability for convenient and rapidbio-assessment there remain debatable issues as to whether the methods for sampling and treating

Water 2016 8 27 15 of 20

macroinvertebrates are effective to provide a reliable and accurate indication of the macroinvertebratefauna throughout the country

The Korean national biomonitoring program presents field sampling in a cost-effective andtime-saving manner for rapid bio-assessment To satisfy this purpose benthic macroinvertebratesare optimized to be collected at riffle andor gliding run habitats using a Surber sampler with threereplicates [27] However such sampling methods probably underestimate overall biodiversity instream ecosystems considering the whole stream environment First single-habitat sampling possiblyproduces incomplete taxa lists and includes no target habitats at certain sites despite its advantagethat the influences of both water and habitat quality on macroinvertebrates are not confounded byinstream habitat variation [57] In this regard a multihabitat approach would be more profitablefor the estimation of taxonomic diversity due to its consistent application across stream typesespecially at large-scaled survey comprehensive taxa lists and effective assessment of ecologicalconditions [58] Second the Surber sampler is one of the most commonly used quantitative toolsin lotic systems and provides high-precision information on the abundance and composition ofmacroinvertebrate assemblages [2159] This method is on the other hand usually more appropriatefor riffle habitats of shallow streams presumably underestimating overall biodiversity in a regionRecent studies on the comparison between sampling devices suggested that artificial substrates(eg leaf-bags) would be used as complementary tools due to their discriminative taxonomiccomposition [60ndash62] Third a majority of biomonitoring programs widely adopt three to five replicatesfor lotic ecosystems because one way to reduce monitoring costs is to decrease the sample size [216364]The previous studies also showed that such a small number of replicates rarely influenced ecologicalhealth assessment particularly for the indices applying sensitivitytolerance taxa as the same forNAEMP [65ndash67] Nevertheless small sample sizes may influence the values of biological measuresand the representativeness for a real benthic community based on the asymptotic relationship ofthe number of taxa with both the sampling area and the collected individuals [68] Finally sievemesh size could also affect the accurate estimates of taxonomic diversity and environmental qualityassessment [67] Finer mesh sizes more accurately represent macroinvertebrate assemblages thancoarser mesh sizes whereas they need more efforts to handle specimens On the contrary coarsermesh sizes undervalue the original density and taxa richness of macroinvertebrate assemblages bypassing small individuals through the sieves and result in higher diversity [69] Considering thetradeoff between cost and effectiveness many rapid bio-assessments determine 05 mm mesh size as areasonable choice [216470] Therefore future researches are required for identifying optimal samplingeffort comprehensively considering cost-effectiveness easy applicability and well representative ofresident macroinvertebrate assemblages

5 Conclusions

Large-scale knowledge on environmental relationships of aquatic communities is crucial toconserve freshwater biodiversity and sustain ecological integrity Korean stream macroinvertebrateassemblages were determined not only by regional and physical instream variables but also bypollution-related parameters at nation-wide scale Macroinvertebrate-based site classification evidentlyprovided an environmental characterization for different types of Korean streams indicating thatbenthic macroinvertebrates are a valuable biomonitoring material The results of this study provideimportant information and a bridge for further work such as the assemblagemdashspecific responses toenvironmental disturbance Our results also contribute to establishing effective management practicesimplementing conservation measures and developing more reliable biological monitoring tools forsustainable freshwater ecosystems

Acknowledgments This study was performed under the project of ldquoNational Aquatic Ecosystem Health Surveyand Assessmentrdquo in Korea and was supported by the Ministry of Environment and the National Institute ofEnvironmental Research Korea The authors are grateful to survey members involved in the project The authorsalso thank the anonymous reviewers for their help in improving the scientific content of the manuscript

Water 2016 8 27 16 of 20

Author Contributions Yung-Chul Jun developed the concept of the study performed data analysis and wrotethe manuscript Nan-Young Kim assisted data processing and figure construction Sang-Hun Kim conductedquality assurance of the physico-chemical and biological data Young-Seuk Park and Dong-Soo Kong assistedstudy design and statistical analysis Soon-Jin Hwang supervised the research and assisted data interpretationand manuscript preparation All the authors contributed to the review of the manuscript

Conflicts of Interest The authors declare no conflict of interest

Appendix A

Table A1 Codes for macroinvertebrates contributing to more than 02 of total abundance for canonicalcorrespondence analysis in Figure 4

Code TaxonPhylum Platyhelminthes

DugSp Dugesia spPhylum Mollusca

SemLi Semisulcospira libertina (Gould)PhyAc Physa acuta Draparnaud

Phylum AnnelidaLimGo Limnodrilus gotoi HataiHirNi Hirudo nipponia Whitman

Phylum ArthropodaClass Crustacea

AseSp Asellus spGamSp Gammarus sp

Class Insecta

Order Ephemeroptera

BaeTu Baetiella tuberculata (Kazlauskas)BaeFu Baetis fuscatus (Linnaeus)BaeUr Baetis ursinus KazlauskasLabAt Labiobaetis atrebatinus (Eaton)NigBa Nigrobaetis bacillus (Kluge)EcdBa Ecdyonurus bajkovae KlugeEcdJo Ecdyonurus joernensis BengtssonEcdKi Ecdyonurus kibunensis ImanishiEcdLe Ecdyonurus levis (Navaacutes)EpeNi Epeorus nipponicus (Ueacuteno)EpeLa Epeorus latifolium (Ueacuteno)EpePe Epeorus pellucidus (Brodsky)ChoAl Choroterpes altioculus KlugeParJa Paraleptophlebia japonica (Matsumura)PotFo Potamanthus formosus EatonRhoCo Rhoenanthus coreanus (Yoon and Bae)DruAc Drunella aculea (Allen)EphOr Ephemera orientalis McLachlanSerSe Serratella setigera (Bajkova)UraPu Uracanthella punctisetae (Matsumura)CaeNi Caenis nishinoae Malzacher

Order Hemiptera

MicSe Micronecta sedula HorvaacutethMicSp Micronecta sp

Order Coleoptera

ElmSp Elmidae spEubKa Eubrianax KUaMatKa Mataeopsephus KUaPseKa Psephenoides KUa

Water 2016 8 27 17 of 20

Table A1 Cont

Code Taxon

Order Diptera

AntKa Antocha KUaCulSp Culex spChiSp Chironomidae spp (non-red type)ChiRe Chironomini spp (red-type)

Order Trichoptera

RhyNi Rhyacophila nigrocephala IwataHydKa Hydroptila KUaGloKa Glossosoma KUaCheBr Cheumatopsyche brevilineata IwataCheKa Cheumatopsyche KUaCheKb Cheumatopsyche KUbHydKo Hydropsyche kozhantschikovi MartynovHydKb Hydropsyche KUbHydOr Hydropsyche orientalis MartynovHydVa Hydropsyche valvata MartynovMacRa Macrostemum radiatum McLachlanPsySp Psychomyia sp

References

1 Dudgeon D Arthington AH Gessner MO Kawabata ZI Knowler DJ Leacutevecircque C Naiman RJPrieur-Richard AH Soto D Stiassny MLJ et al Freshwater biodiversity Importance threats status andconservation challenges Biol Rev 2006 81 163ndash182 [CrossRef] [PubMed]

2 Strayer DL Dudgeon D Freshwater biodiversity conservation Recent progress and future challengesJ N Am Benthol Soc 2010 29 344ndash358 [CrossRef]

3 Li F Chung N Bae M-J Kwon Y-S Park Y-S Relationships between stream macroinvertebrates andenvironmental variables at multiple spatial scales Freshwater Biol 2012 57 2107ndash2124 [CrossRef]

4 Dudgeon D The ecology of tropical Asian rivers and streams in relation to biodiversity conservationAnnu Rev Ecol Syst 2000 31 239ndash263 [CrossRef]

5 De Silva SS Abery NW Nguyen TTT Endemic freshwater finfish of Asia Distribution and conservationstatus Divers Distrib 2007 13 172ndash184 [CrossRef]

6 Voumlroumlsmarty CJ McIntyre PB Gessner MO Dudgeon D Prusevich A Green P Glidden S Bunn SESullivan CA Liermann CE et al Global threats to human water security and river biodiversity Nature2010 467 555ndash561 [CrossRef] [PubMed]

7 Strayer DL Challenges for freshwater invertebrate conservation J N Am Benthol Soc 2006 25 271ndash287[CrossRef]

8 Buss DF Baptista DF Silveira MP Nessimian JL Dorvilleacute LFM Influence of water chemistryand environmental degradation on macroinvertebrate assemblages in a river basin in south-east BrazilHydrobiologia 2002 481 125ndash136 [CrossRef]

9 Bott TL Brock JT Dunn CS Naiman RJ Ovink RW Petersen RC Benthic community metabolism infour temperate stream systems An inter-biome comparison and evaluation of the river continuum conceptHydrobiologia 1985 220 109ndash117 [CrossRef]

10 Merz JR Ochikubo Chan LK Effects of gravel augmentation on macroinvertebrate assemblages in aregulated California river River Res Appl 2005 21 61ndash74 [CrossRef]

11 Nelson SM Lieberman DM The influence of flow and other environmental factors on benthic invertebratesin the Sacramento River USA Hydrobiologia 2002 489 117ndash129 [CrossRef]

12 Jiang XM Xiong J Qiu JW Wu JM Wang JW Xie ZC Structure of macroinvertebrate communitiesin relation to environmental variables in a subtropical Asian river system Int Rev Hydrobiol 2010 95 42ndash57[CrossRef]

Water 2016 8 27 14 of 20

associations with physical variables and biological attributes such as taxa richness EPT richnessEPT abundance and the Shannon diversity index This may be due to the fact that over half ofthe studied streams corresponded to lowland streams below 100 m asl which were characterizedby moderate or slightly poor water quality with severe variations in BOD TN TP and Shannondiversity-based saprobity [3651] (Table 1) Harding et al [52] demonstrated that increasing humanland use intensity along a river continuum caused water quality degradation consequently leadingto changes in taxonomic composition from intolerant EPT dominated to tolerant taxa-dominatedassemblages despite a gradual increase in taxa abundance by a few dominant species

Riffle habitats are commonly characterized by shallow water depth oxygenating fast-flowingwater and stony beds and exhibit higher taxa richness and abundance than that at pools or habitatswith fine sediment as in our case [34253] Such hydraulic conditions are critical determinantsfor the distribution and species composition of benthic organisms [1654] and are the drivingforces for evolution of their morphologies and life history [11] Rheophilous (ie having an affinityfor running waters) and limnophilous taxa were clearly discriminated based on the correlationanalysis (Figure 2) and CCA (Figure 4) results For example well-known rhithronic species intwo Ephemeropteran (Ephemerellidae and Heptageniidae) and one Trichopteran (Hydropsychidae)families mostly displayed high preference to the mid- or fast current conditions which corresponds tothe intolerant scraper or filtering collector groups abundant in upper and middle stream reaches [49]Thus biological monitoring and assessment programs using rheophilic macroinvertebrates wouldbenefit from their ecological characteristics and their indication of good environmental quality(eg [42]) although seasonal fluctuations in hydraulic parameters by the Asian monsoon more criticallycause a catastrophic drift and washout of benthic organisms

Streambed composition is one of the most important factors to directly influence richness andabundance of macroinvertebrates on local scales [1216] thus close correlations would be expectedwith variables related to longitudinal changes in stream ecosystems Boulders and cobbles aretypically the major structural elements in steep gradient upper streams whereas sand and smallersediments predominate in the lower reaches [55] There have been a large number of studies onthe macroinvertebrate-substrate relationship most of which have revealed that macroinvertebratediversity and density increase with higher heterogeneity due to the available stable and diversemicrohabitats (eg [1043]) Therefore factors determining macroinvertebrate communities at localscales obviously put a priority on the streambed conditions rather than water quality or other physicalvariables We found that the mainstreams of the Nakdong River which contained about 60 fineparticles retained the lowest taxa richness (82 on average n = 18) and abundance (747 individualsm2)among five major rivers despite its good water quality condition (mean BOD 19 and TN 18 mgL)with the exception of the severely polluted Youngsan River (89 taxa richness and 73 BOD n = 13)These results indicate that homogeneous streambeds with greater fine particles support lower diversityand abundance even when streams maintain good water quality [56] Additionally organic pollutioncould transform the coarse substrate into an organic rich soft bottom altering the community structurefrom dominated by diverse and intolerant species to communities predominated by a few tolerantspecies [320] as in the case of the Youngsan River

43 Considerations to Improve Macroinvertebrate Biomonitoring Programs

Not until 2006 did Korea adopt biological water quality criteria and the concept of ecologicalintegrity in the water quality program [2536] Since then Korean government has led a biologicalsurvey of streams and rivers (ie NAEMP) every year to assess the current biological status of streamand river ecosystems and to develop a strategy for the restoration and management of disturbedsystems [25] As a part of a nationwide survey benthic macroinvertebrates are also monitored based onthe guidelines and assessment tools [27] Notwithstanding their suitability for convenient and rapidbio-assessment there remain debatable issues as to whether the methods for sampling and treating

Water 2016 8 27 15 of 20

macroinvertebrates are effective to provide a reliable and accurate indication of the macroinvertebratefauna throughout the country

The Korean national biomonitoring program presents field sampling in a cost-effective andtime-saving manner for rapid bio-assessment To satisfy this purpose benthic macroinvertebratesare optimized to be collected at riffle andor gliding run habitats using a Surber sampler with threereplicates [27] However such sampling methods probably underestimate overall biodiversity instream ecosystems considering the whole stream environment First single-habitat sampling possiblyproduces incomplete taxa lists and includes no target habitats at certain sites despite its advantagethat the influences of both water and habitat quality on macroinvertebrates are not confounded byinstream habitat variation [57] In this regard a multihabitat approach would be more profitablefor the estimation of taxonomic diversity due to its consistent application across stream typesespecially at large-scaled survey comprehensive taxa lists and effective assessment of ecologicalconditions [58] Second the Surber sampler is one of the most commonly used quantitative toolsin lotic systems and provides high-precision information on the abundance and composition ofmacroinvertebrate assemblages [2159] This method is on the other hand usually more appropriatefor riffle habitats of shallow streams presumably underestimating overall biodiversity in a regionRecent studies on the comparison between sampling devices suggested that artificial substrates(eg leaf-bags) would be used as complementary tools due to their discriminative taxonomiccomposition [60ndash62] Third a majority of biomonitoring programs widely adopt three to five replicatesfor lotic ecosystems because one way to reduce monitoring costs is to decrease the sample size [216364]The previous studies also showed that such a small number of replicates rarely influenced ecologicalhealth assessment particularly for the indices applying sensitivitytolerance taxa as the same forNAEMP [65ndash67] Nevertheless small sample sizes may influence the values of biological measuresand the representativeness for a real benthic community based on the asymptotic relationship ofthe number of taxa with both the sampling area and the collected individuals [68] Finally sievemesh size could also affect the accurate estimates of taxonomic diversity and environmental qualityassessment [67] Finer mesh sizes more accurately represent macroinvertebrate assemblages thancoarser mesh sizes whereas they need more efforts to handle specimens On the contrary coarsermesh sizes undervalue the original density and taxa richness of macroinvertebrate assemblages bypassing small individuals through the sieves and result in higher diversity [69] Considering thetradeoff between cost and effectiveness many rapid bio-assessments determine 05 mm mesh size as areasonable choice [216470] Therefore future researches are required for identifying optimal samplingeffort comprehensively considering cost-effectiveness easy applicability and well representative ofresident macroinvertebrate assemblages

5 Conclusions

Large-scale knowledge on environmental relationships of aquatic communities is crucial toconserve freshwater biodiversity and sustain ecological integrity Korean stream macroinvertebrateassemblages were determined not only by regional and physical instream variables but also bypollution-related parameters at nation-wide scale Macroinvertebrate-based site classification evidentlyprovided an environmental characterization for different types of Korean streams indicating thatbenthic macroinvertebrates are a valuable biomonitoring material The results of this study provideimportant information and a bridge for further work such as the assemblagemdashspecific responses toenvironmental disturbance Our results also contribute to establishing effective management practicesimplementing conservation measures and developing more reliable biological monitoring tools forsustainable freshwater ecosystems

Acknowledgments This study was performed under the project of ldquoNational Aquatic Ecosystem Health Surveyand Assessmentrdquo in Korea and was supported by the Ministry of Environment and the National Institute ofEnvironmental Research Korea The authors are grateful to survey members involved in the project The authorsalso thank the anonymous reviewers for their help in improving the scientific content of the manuscript

Water 2016 8 27 16 of 20

Author Contributions Yung-Chul Jun developed the concept of the study performed data analysis and wrotethe manuscript Nan-Young Kim assisted data processing and figure construction Sang-Hun Kim conductedquality assurance of the physico-chemical and biological data Young-Seuk Park and Dong-Soo Kong assistedstudy design and statistical analysis Soon-Jin Hwang supervised the research and assisted data interpretationand manuscript preparation All the authors contributed to the review of the manuscript

Conflicts of Interest The authors declare no conflict of interest

Appendix A

Table A1 Codes for macroinvertebrates contributing to more than 02 of total abundance for canonicalcorrespondence analysis in Figure 4

Code TaxonPhylum Platyhelminthes

DugSp Dugesia spPhylum Mollusca

SemLi Semisulcospira libertina (Gould)PhyAc Physa acuta Draparnaud

Phylum AnnelidaLimGo Limnodrilus gotoi HataiHirNi Hirudo nipponia Whitman

Phylum ArthropodaClass Crustacea

AseSp Asellus spGamSp Gammarus sp

Class Insecta

Order Ephemeroptera

BaeTu Baetiella tuberculata (Kazlauskas)BaeFu Baetis fuscatus (Linnaeus)BaeUr Baetis ursinus KazlauskasLabAt Labiobaetis atrebatinus (Eaton)NigBa Nigrobaetis bacillus (Kluge)EcdBa Ecdyonurus bajkovae KlugeEcdJo Ecdyonurus joernensis BengtssonEcdKi Ecdyonurus kibunensis ImanishiEcdLe Ecdyonurus levis (Navaacutes)EpeNi Epeorus nipponicus (Ueacuteno)EpeLa Epeorus latifolium (Ueacuteno)EpePe Epeorus pellucidus (Brodsky)ChoAl Choroterpes altioculus KlugeParJa Paraleptophlebia japonica (Matsumura)PotFo Potamanthus formosus EatonRhoCo Rhoenanthus coreanus (Yoon and Bae)DruAc Drunella aculea (Allen)EphOr Ephemera orientalis McLachlanSerSe Serratella setigera (Bajkova)UraPu Uracanthella punctisetae (Matsumura)CaeNi Caenis nishinoae Malzacher

Order Hemiptera

MicSe Micronecta sedula HorvaacutethMicSp Micronecta sp

Order Coleoptera

ElmSp Elmidae spEubKa Eubrianax KUaMatKa Mataeopsephus KUaPseKa Psephenoides KUa

Water 2016 8 27 17 of 20

Table A1 Cont

Code Taxon

Order Diptera

AntKa Antocha KUaCulSp Culex spChiSp Chironomidae spp (non-red type)ChiRe Chironomini spp (red-type)

Order Trichoptera

RhyNi Rhyacophila nigrocephala IwataHydKa Hydroptila KUaGloKa Glossosoma KUaCheBr Cheumatopsyche brevilineata IwataCheKa Cheumatopsyche KUaCheKb Cheumatopsyche KUbHydKo Hydropsyche kozhantschikovi MartynovHydKb Hydropsyche KUbHydOr Hydropsyche orientalis MartynovHydVa Hydropsyche valvata MartynovMacRa Macrostemum radiatum McLachlanPsySp Psychomyia sp

References

1 Dudgeon D Arthington AH Gessner MO Kawabata ZI Knowler DJ Leacutevecircque C Naiman RJPrieur-Richard AH Soto D Stiassny MLJ et al Freshwater biodiversity Importance threats status andconservation challenges Biol Rev 2006 81 163ndash182 [CrossRef] [PubMed]

2 Strayer DL Dudgeon D Freshwater biodiversity conservation Recent progress and future challengesJ N Am Benthol Soc 2010 29 344ndash358 [CrossRef]

3 Li F Chung N Bae M-J Kwon Y-S Park Y-S Relationships between stream macroinvertebrates andenvironmental variables at multiple spatial scales Freshwater Biol 2012 57 2107ndash2124 [CrossRef]

4 Dudgeon D The ecology of tropical Asian rivers and streams in relation to biodiversity conservationAnnu Rev Ecol Syst 2000 31 239ndash263 [CrossRef]

5 De Silva SS Abery NW Nguyen TTT Endemic freshwater finfish of Asia Distribution and conservationstatus Divers Distrib 2007 13 172ndash184 [CrossRef]

6 Voumlroumlsmarty CJ McIntyre PB Gessner MO Dudgeon D Prusevich A Green P Glidden S Bunn SESullivan CA Liermann CE et al Global threats to human water security and river biodiversity Nature2010 467 555ndash561 [CrossRef] [PubMed]

7 Strayer DL Challenges for freshwater invertebrate conservation J N Am Benthol Soc 2006 25 271ndash287[CrossRef]

8 Buss DF Baptista DF Silveira MP Nessimian JL Dorvilleacute LFM Influence of water chemistryand environmental degradation on macroinvertebrate assemblages in a river basin in south-east BrazilHydrobiologia 2002 481 125ndash136 [CrossRef]

9 Bott TL Brock JT Dunn CS Naiman RJ Ovink RW Petersen RC Benthic community metabolism infour temperate stream systems An inter-biome comparison and evaluation of the river continuum conceptHydrobiologia 1985 220 109ndash117 [CrossRef]

10 Merz JR Ochikubo Chan LK Effects of gravel augmentation on macroinvertebrate assemblages in aregulated California river River Res Appl 2005 21 61ndash74 [CrossRef]

11 Nelson SM Lieberman DM The influence of flow and other environmental factors on benthic invertebratesin the Sacramento River USA Hydrobiologia 2002 489 117ndash129 [CrossRef]

12 Jiang XM Xiong J Qiu JW Wu JM Wang JW Xie ZC Structure of macroinvertebrate communitiesin relation to environmental variables in a subtropical Asian river system Int Rev Hydrobiol 2010 95 42ndash57[CrossRef]

Water 2016 8 27 15 of 20

macroinvertebrates are effective to provide a reliable and accurate indication of the macroinvertebratefauna throughout the country

The Korean national biomonitoring program presents field sampling in a cost-effective andtime-saving manner for rapid bio-assessment To satisfy this purpose benthic macroinvertebratesare optimized to be collected at riffle andor gliding run habitats using a Surber sampler with threereplicates [27] However such sampling methods probably underestimate overall biodiversity instream ecosystems considering the whole stream environment First single-habitat sampling possiblyproduces incomplete taxa lists and includes no target habitats at certain sites despite its advantagethat the influences of both water and habitat quality on macroinvertebrates are not confounded byinstream habitat variation [57] In this regard a multihabitat approach would be more profitablefor the estimation of taxonomic diversity due to its consistent application across stream typesespecially at large-scaled survey comprehensive taxa lists and effective assessment of ecologicalconditions [58] Second the Surber sampler is one of the most commonly used quantitative toolsin lotic systems and provides high-precision information on the abundance and composition ofmacroinvertebrate assemblages [2159] This method is on the other hand usually more appropriatefor riffle habitats of shallow streams presumably underestimating overall biodiversity in a regionRecent studies on the comparison between sampling devices suggested that artificial substrates(eg leaf-bags) would be used as complementary tools due to their discriminative taxonomiccomposition [60ndash62] Third a majority of biomonitoring programs widely adopt three to five replicatesfor lotic ecosystems because one way to reduce monitoring costs is to decrease the sample size [216364]The previous studies also showed that such a small number of replicates rarely influenced ecologicalhealth assessment particularly for the indices applying sensitivitytolerance taxa as the same forNAEMP [65ndash67] Nevertheless small sample sizes may influence the values of biological measuresand the representativeness for a real benthic community based on the asymptotic relationship ofthe number of taxa with both the sampling area and the collected individuals [68] Finally sievemesh size could also affect the accurate estimates of taxonomic diversity and environmental qualityassessment [67] Finer mesh sizes more accurately represent macroinvertebrate assemblages thancoarser mesh sizes whereas they need more efforts to handle specimens On the contrary coarsermesh sizes undervalue the original density and taxa richness of macroinvertebrate assemblages bypassing small individuals through the sieves and result in higher diversity [69] Considering thetradeoff between cost and effectiveness many rapid bio-assessments determine 05 mm mesh size as areasonable choice [216470] Therefore future researches are required for identifying optimal samplingeffort comprehensively considering cost-effectiveness easy applicability and well representative ofresident macroinvertebrate assemblages

5 Conclusions

Large-scale knowledge on environmental relationships of aquatic communities is crucial toconserve freshwater biodiversity and sustain ecological integrity Korean stream macroinvertebrateassemblages were determined not only by regional and physical instream variables but also bypollution-related parameters at nation-wide scale Macroinvertebrate-based site classification evidentlyprovided an environmental characterization for different types of Korean streams indicating thatbenthic macroinvertebrates are a valuable biomonitoring material The results of this study provideimportant information and a bridge for further work such as the assemblagemdashspecific responses toenvironmental disturbance Our results also contribute to establishing effective management practicesimplementing conservation measures and developing more reliable biological monitoring tools forsustainable freshwater ecosystems

Acknowledgments This study was performed under the project of ldquoNational Aquatic Ecosystem Health Surveyand Assessmentrdquo in Korea and was supported by the Ministry of Environment and the National Institute ofEnvironmental Research Korea The authors are grateful to survey members involved in the project The authorsalso thank the anonymous reviewers for their help in improving the scientific content of the manuscript

Water 2016 8 27 16 of 20

Author Contributions Yung-Chul Jun developed the concept of the study performed data analysis and wrotethe manuscript Nan-Young Kim assisted data processing and figure construction Sang-Hun Kim conductedquality assurance of the physico-chemical and biological data Young-Seuk Park and Dong-Soo Kong assistedstudy design and statistical analysis Soon-Jin Hwang supervised the research and assisted data interpretationand manuscript preparation All the authors contributed to the review of the manuscript

Conflicts of Interest The authors declare no conflict of interest

Appendix A

Table A1 Codes for macroinvertebrates contributing to more than 02 of total abundance for canonicalcorrespondence analysis in Figure 4

Code TaxonPhylum Platyhelminthes

DugSp Dugesia spPhylum Mollusca

SemLi Semisulcospira libertina (Gould)PhyAc Physa acuta Draparnaud

Phylum AnnelidaLimGo Limnodrilus gotoi HataiHirNi Hirudo nipponia Whitman

Phylum ArthropodaClass Crustacea

AseSp Asellus spGamSp Gammarus sp

Class Insecta

Order Ephemeroptera

BaeTu Baetiella tuberculata (Kazlauskas)BaeFu Baetis fuscatus (Linnaeus)BaeUr Baetis ursinus KazlauskasLabAt Labiobaetis atrebatinus (Eaton)NigBa Nigrobaetis bacillus (Kluge)EcdBa Ecdyonurus bajkovae KlugeEcdJo Ecdyonurus joernensis BengtssonEcdKi Ecdyonurus kibunensis ImanishiEcdLe Ecdyonurus levis (Navaacutes)EpeNi Epeorus nipponicus (Ueacuteno)EpeLa Epeorus latifolium (Ueacuteno)EpePe Epeorus pellucidus (Brodsky)ChoAl Choroterpes altioculus KlugeParJa Paraleptophlebia japonica (Matsumura)PotFo Potamanthus formosus EatonRhoCo Rhoenanthus coreanus (Yoon and Bae)DruAc Drunella aculea (Allen)EphOr Ephemera orientalis McLachlanSerSe Serratella setigera (Bajkova)UraPu Uracanthella punctisetae (Matsumura)CaeNi Caenis nishinoae Malzacher

Order Hemiptera

MicSe Micronecta sedula HorvaacutethMicSp Micronecta sp

Order Coleoptera

ElmSp Elmidae spEubKa Eubrianax KUaMatKa Mataeopsephus KUaPseKa Psephenoides KUa

Water 2016 8 27 17 of 20

Table A1 Cont

Code Taxon

Order Diptera

AntKa Antocha KUaCulSp Culex spChiSp Chironomidae spp (non-red type)ChiRe Chironomini spp (red-type)

Order Trichoptera

RhyNi Rhyacophila nigrocephala IwataHydKa Hydroptila KUaGloKa Glossosoma KUaCheBr Cheumatopsyche brevilineata IwataCheKa Cheumatopsyche KUaCheKb Cheumatopsyche KUbHydKo Hydropsyche kozhantschikovi MartynovHydKb Hydropsyche KUbHydOr Hydropsyche orientalis MartynovHydVa Hydropsyche valvata MartynovMacRa Macrostemum radiatum McLachlanPsySp Psychomyia sp

References

1 Dudgeon D Arthington AH Gessner MO Kawabata ZI Knowler DJ Leacutevecircque C Naiman RJPrieur-Richard AH Soto D Stiassny MLJ et al Freshwater biodiversity Importance threats status andconservation challenges Biol Rev 2006 81 163ndash182 [CrossRef] [PubMed]

2 Strayer DL Dudgeon D Freshwater biodiversity conservation Recent progress and future challengesJ N Am Benthol Soc 2010 29 344ndash358 [CrossRef]

3 Li F Chung N Bae M-J Kwon Y-S Park Y-S Relationships between stream macroinvertebrates andenvironmental variables at multiple spatial scales Freshwater Biol 2012 57 2107ndash2124 [CrossRef]

4 Dudgeon D The ecology of tropical Asian rivers and streams in relation to biodiversity conservationAnnu Rev Ecol Syst 2000 31 239ndash263 [CrossRef]

5 De Silva SS Abery NW Nguyen TTT Endemic freshwater finfish of Asia Distribution and conservationstatus Divers Distrib 2007 13 172ndash184 [CrossRef]

6 Voumlroumlsmarty CJ McIntyre PB Gessner MO Dudgeon D Prusevich A Green P Glidden S Bunn SESullivan CA Liermann CE et al Global threats to human water security and river biodiversity Nature2010 467 555ndash561 [CrossRef] [PubMed]

7 Strayer DL Challenges for freshwater invertebrate conservation J N Am Benthol Soc 2006 25 271ndash287[CrossRef]

8 Buss DF Baptista DF Silveira MP Nessimian JL Dorvilleacute LFM Influence of water chemistryand environmental degradation on macroinvertebrate assemblages in a river basin in south-east BrazilHydrobiologia 2002 481 125ndash136 [CrossRef]

9 Bott TL Brock JT Dunn CS Naiman RJ Ovink RW Petersen RC Benthic community metabolism infour temperate stream systems An inter-biome comparison and evaluation of the river continuum conceptHydrobiologia 1985 220 109ndash117 [CrossRef]

10 Merz JR Ochikubo Chan LK Effects of gravel augmentation on macroinvertebrate assemblages in aregulated California river River Res Appl 2005 21 61ndash74 [CrossRef]

11 Nelson SM Lieberman DM The influence of flow and other environmental factors on benthic invertebratesin the Sacramento River USA Hydrobiologia 2002 489 117ndash129 [CrossRef]

12 Jiang XM Xiong J Qiu JW Wu JM Wang JW Xie ZC Structure of macroinvertebrate communitiesin relation to environmental variables in a subtropical Asian river system Int Rev Hydrobiol 2010 95 42ndash57[CrossRef]

Water 2016 8 27 16 of 20

Author Contributions Yung-Chul Jun developed the concept of the study performed data analysis and wrotethe manuscript Nan-Young Kim assisted data processing and figure construction Sang-Hun Kim conductedquality assurance of the physico-chemical and biological data Young-Seuk Park and Dong-Soo Kong assistedstudy design and statistical analysis Soon-Jin Hwang supervised the research and assisted data interpretationand manuscript preparation All the authors contributed to the review of the manuscript

Conflicts of Interest The authors declare no conflict of interest

Appendix A

Table A1 Codes for macroinvertebrates contributing to more than 02 of total abundance for canonicalcorrespondence analysis in Figure 4

Code TaxonPhylum Platyhelminthes

DugSp Dugesia spPhylum Mollusca

SemLi Semisulcospira libertina (Gould)PhyAc Physa acuta Draparnaud

Phylum AnnelidaLimGo Limnodrilus gotoi HataiHirNi Hirudo nipponia Whitman

Phylum ArthropodaClass Crustacea

AseSp Asellus spGamSp Gammarus sp

Class Insecta

Order Ephemeroptera

BaeTu Baetiella tuberculata (Kazlauskas)BaeFu Baetis fuscatus (Linnaeus)BaeUr Baetis ursinus KazlauskasLabAt Labiobaetis atrebatinus (Eaton)NigBa Nigrobaetis bacillus (Kluge)EcdBa Ecdyonurus bajkovae KlugeEcdJo Ecdyonurus joernensis BengtssonEcdKi Ecdyonurus kibunensis ImanishiEcdLe Ecdyonurus levis (Navaacutes)EpeNi Epeorus nipponicus (Ueacuteno)EpeLa Epeorus latifolium (Ueacuteno)EpePe Epeorus pellucidus (Brodsky)ChoAl Choroterpes altioculus KlugeParJa Paraleptophlebia japonica (Matsumura)PotFo Potamanthus formosus EatonRhoCo Rhoenanthus coreanus (Yoon and Bae)DruAc Drunella aculea (Allen)EphOr Ephemera orientalis McLachlanSerSe Serratella setigera (Bajkova)UraPu Uracanthella punctisetae (Matsumura)CaeNi Caenis nishinoae Malzacher

Order Hemiptera

MicSe Micronecta sedula HorvaacutethMicSp Micronecta sp

Order Coleoptera

ElmSp Elmidae spEubKa Eubrianax KUaMatKa Mataeopsephus KUaPseKa Psephenoides KUa

Water 2016 8 27 17 of 20

Table A1 Cont

Code Taxon

Order Diptera

AntKa Antocha KUaCulSp Culex spChiSp Chironomidae spp (non-red type)ChiRe Chironomini spp (red-type)

Order Trichoptera

RhyNi Rhyacophila nigrocephala IwataHydKa Hydroptila KUaGloKa Glossosoma KUaCheBr Cheumatopsyche brevilineata IwataCheKa Cheumatopsyche KUaCheKb Cheumatopsyche KUbHydKo Hydropsyche kozhantschikovi MartynovHydKb Hydropsyche KUbHydOr Hydropsyche orientalis MartynovHydVa Hydropsyche valvata MartynovMacRa Macrostemum radiatum McLachlanPsySp Psychomyia sp

References

1 Dudgeon D Arthington AH Gessner MO Kawabata ZI Knowler DJ Leacutevecircque C Naiman RJPrieur-Richard AH Soto D Stiassny MLJ et al Freshwater biodiversity Importance threats status andconservation challenges Biol Rev 2006 81 163ndash182 [CrossRef] [PubMed]

2 Strayer DL Dudgeon D Freshwater biodiversity conservation Recent progress and future challengesJ N Am Benthol Soc 2010 29 344ndash358 [CrossRef]

3 Li F Chung N Bae M-J Kwon Y-S Park Y-S Relationships between stream macroinvertebrates andenvironmental variables at multiple spatial scales Freshwater Biol 2012 57 2107ndash2124 [CrossRef]

4 Dudgeon D The ecology of tropical Asian rivers and streams in relation to biodiversity conservationAnnu Rev Ecol Syst 2000 31 239ndash263 [CrossRef]

5 De Silva SS Abery NW Nguyen TTT Endemic freshwater finfish of Asia Distribution and conservationstatus Divers Distrib 2007 13 172ndash184 [CrossRef]

6 Voumlroumlsmarty CJ McIntyre PB Gessner MO Dudgeon D Prusevich A Green P Glidden S Bunn SESullivan CA Liermann CE et al Global threats to human water security and river biodiversity Nature2010 467 555ndash561 [CrossRef] [PubMed]

7 Strayer DL Challenges for freshwater invertebrate conservation J N Am Benthol Soc 2006 25 271ndash287[CrossRef]

8 Buss DF Baptista DF Silveira MP Nessimian JL Dorvilleacute LFM Influence of water chemistryand environmental degradation on macroinvertebrate assemblages in a river basin in south-east BrazilHydrobiologia 2002 481 125ndash136 [CrossRef]

9 Bott TL Brock JT Dunn CS Naiman RJ Ovink RW Petersen RC Benthic community metabolism infour temperate stream systems An inter-biome comparison and evaluation of the river continuum conceptHydrobiologia 1985 220 109ndash117 [CrossRef]

10 Merz JR Ochikubo Chan LK Effects of gravel augmentation on macroinvertebrate assemblages in aregulated California river River Res Appl 2005 21 61ndash74 [CrossRef]

11 Nelson SM Lieberman DM The influence of flow and other environmental factors on benthic invertebratesin the Sacramento River USA Hydrobiologia 2002 489 117ndash129 [CrossRef]

12 Jiang XM Xiong J Qiu JW Wu JM Wang JW Xie ZC Structure of macroinvertebrate communitiesin relation to environmental variables in a subtropical Asian river system Int Rev Hydrobiol 2010 95 42ndash57[CrossRef]

Water 2016 8 27 17 of 20

Table A1 Cont

Code Taxon

Order Diptera

AntKa Antocha KUaCulSp Culex spChiSp Chironomidae spp (non-red type)ChiRe Chironomini spp (red-type)

Order Trichoptera

RhyNi Rhyacophila nigrocephala IwataHydKa Hydroptila KUaGloKa Glossosoma KUaCheBr Cheumatopsyche brevilineata IwataCheKa Cheumatopsyche KUaCheKb Cheumatopsyche KUbHydKo Hydropsyche kozhantschikovi MartynovHydKb Hydropsyche KUbHydOr Hydropsyche orientalis MartynovHydVa Hydropsyche valvata MartynovMacRa Macrostemum radiatum McLachlanPsySp Psychomyia sp

References

1 Dudgeon D Arthington AH Gessner MO Kawabata ZI Knowler DJ Leacutevecircque C Naiman RJPrieur-Richard AH Soto D Stiassny MLJ et al Freshwater biodiversity Importance threats status andconservation challenges Biol Rev 2006 81 163ndash182 [CrossRef] [PubMed]

2 Strayer DL Dudgeon D Freshwater biodiversity conservation Recent progress and future challengesJ N Am Benthol Soc 2010 29 344ndash358 [CrossRef]

3 Li F Chung N Bae M-J Kwon Y-S Park Y-S Relationships between stream macroinvertebrates andenvironmental variables at multiple spatial scales Freshwater Biol 2012 57 2107ndash2124 [CrossRef]

4 Dudgeon D The ecology of tropical Asian rivers and streams in relation to biodiversity conservationAnnu Rev Ecol Syst 2000 31 239ndash263 [CrossRef]

5 De Silva SS Abery NW Nguyen TTT Endemic freshwater finfish of Asia Distribution and conservationstatus Divers Distrib 2007 13 172ndash184 [CrossRef]

6 Voumlroumlsmarty CJ McIntyre PB Gessner MO Dudgeon D Prusevich A Green P Glidden S Bunn SESullivan CA Liermann CE et al Global threats to human water security and river biodiversity Nature2010 467 555ndash561 [CrossRef] [PubMed]

7 Strayer DL Challenges for freshwater invertebrate conservation J N Am Benthol Soc 2006 25 271ndash287[CrossRef]

8 Buss DF Baptista DF Silveira MP Nessimian JL Dorvilleacute LFM Influence of water chemistryand environmental degradation on macroinvertebrate assemblages in a river basin in south-east BrazilHydrobiologia 2002 481 125ndash136 [CrossRef]

9 Bott TL Brock JT Dunn CS Naiman RJ Ovink RW Petersen RC Benthic community metabolism infour temperate stream systems An inter-biome comparison and evaluation of the river continuum conceptHydrobiologia 1985 220 109ndash117 [CrossRef]

10 Merz JR Ochikubo Chan LK Effects of gravel augmentation on macroinvertebrate assemblages in aregulated California river River Res Appl 2005 21 61ndash74 [CrossRef]

11 Nelson SM Lieberman DM The influence of flow and other environmental factors on benthic invertebratesin the Sacramento River USA Hydrobiologia 2002 489 117ndash129 [CrossRef]

12 Jiang XM Xiong J Qiu JW Wu JM Wang JW Xie ZC Structure of macroinvertebrate communitiesin relation to environmental variables in a subtropical Asian river system Int Rev Hydrobiol 2010 95 42ndash57[CrossRef]

Water 2016 8 27 18 of 20

13 Vought LBM Kullberg A Petersen RC Effect of riparian structure temperature and channelmorphometry on detritus processing in channelized and natural woodland streams in southern SwedenAquat Conserv Mar Freshw Ecosyst 1998 8 273ndash285 [CrossRef]

14 Townsend CR Hildrew AG Francis J Community structure in some southern English streams Theinfluence of physicochemical factors Freshw Biol 1983 13 521ndash544 [CrossRef]

15 Richards C Haro RJ Johnson LB Host GE Catchment and reach-scale properties as indicator ofmacroinvertebrate species traits Freshw Biol 1997 37 219ndash230 [CrossRef]

16 Sandin L Benthic macroinvertebrates in Swedish streams Community structure taxon richness andenvironmental relations Ecography 2003 26 269ndash282 [CrossRef]

17 Leps M Tonkin JD Dahm V Haase P Sundermann A Disentangling environmental drivers of benthicinvertebrate assemblages The role of spatial scale and riverscape heterogeneity in a multiple stressorenvironment Sci Total Environ 2015 536 546ndash556 [CrossRef] [PubMed]

18 Heino J Biodiversity of aquatic insects Spatial gradients and environmental correlates of assemblage-levelmeasures at large scales Freshw Rev 2009 2 1ndash29 [CrossRef]

19 Shah DN Tonkin JD Haase P Jaumlhnig SC Latitudinal patterns and large-scale environmentaldeterminants of stream insect richness across Europe Limnologica 2015 55 33ndash43 [CrossRef]

20 Rossaro B Pietrangelo A Macroinvertebrate distribution in streams A comparison of CA ordination withbiotic indices Hydrobiologia 1993 263 109ndash118 [CrossRef]

21 Rosenberg DM Resh VH Freshwater Biomonitoring and Benthic Macroinvertebrates Chapman and HallNew York NY USA 1993

22 Charvet S Statzner B Usseglio-Polatera P Dumont B Traits of benthic macroinvertebrates in semi-naturalFrench streams An initial application to biomonitoring in Europe Freshw Biol 2000 43 277ndash296 [CrossRef]

23 Korea Meteorological Administration (KMA) The Meteorological Yearbook in Korea KMA Seoul Korea 2010(in Korean)

24 Jeong KS Hong DG Byeon MS Jeong JC Kim HG Kim DK Joo GJ Stream modification patternsin a river basin Field survey and self-organizing map (SOM) application Ecol Inform 2010 5 293ndash303[CrossRef]

25 Hwang S-J Kim J-Y Yoon S-A Kim B-H Park M-H You K-A Lee H-Y Kim H-S Kim Y-JLee J et al Distribution of benthic diatoms in Korean rivers and streams in relation to environmentalvariables Ann Limnol Int J Limnol 2011 47 S15ndashS33 [CrossRef]

26 Craig DA Some of what you should know about water Bull N Am Benthol Soc 1987 4 178ndash18227 The Ministry of EnvironmentNational Institute of Environmental Research (MOENIER) Survey and

Evaluation of Aquatic Ecosystem Health in Korea MOENIER Incheon Korea 201228 American Public Health Association (APHA) Standard Methods for the Examination of Water and Wastewater

21st ed APHA Washington DC USA 200129 McCune B Grace JB Analysis of Ecological Communities MjM Software Design Gleneden Beach

OR USA 200230 Mielke PW Berry KJ Johnson ES Multiresponse permutation procedures for a priori classifications

Commun Stat 1976 A5 1409ndash1424 [CrossRef]31 Zimmerman GM Goetz H Mielke PW Use of an improved statistical method for group comparisons to

study effects of prairie fire Ecology 1985 66 606ndash611 [CrossRef]32 Dufrene M Legendre P Species assemblages and indicator species The need for flexible asymmetrical

approach Ecol Monogr 1997 67 345ndash366 [CrossRef]33 Petersen WT Keister JE Interannual variability in copepod community composition at a coastal station in

the northern California Current A multivariate approach Deep Sea Res 2003 50 2499ndash2517 [CrossRef]34 McCune B Mefford MJ Multivariate Analysis of Ecological Data (Version 425) MjM Software Gleneden

Beach OR USA 199935 Wang X Cai Q Tang T Yang S Li F Spatial distribution of benthic macroinvertebrates in the Erhai

basin of southwestern China J Freshw Ecol 2012 27 89ndash96 [CrossRef]36 Lee S-W Hwang S-J Lee J-K Jung D-I Park Y-J Kim J-T Overview and application of the National

Aquatic Ecological Monitoring Program (NAEMP) in Korea Ann Limnol Int J Limnol 2011 47 S3ndashS14[CrossRef]

Water 2016 8 27 19 of 20

37 Hoang TH Lock K Chi Dang K de Pauw N Goethals PLM Spatial and temporal patterns ofmacroinvertebrate communities in the Du River Basin in Northern Vietnam J Freshw Ecol 2010 25 637ndash647[CrossRef]

38 Bae M-J Kwon Y Hwang S-J Con T-S Yang H-J Kwak I-S Park J-H Ham S-A Park Y-SRelationships between three major stream assemblages and their environmental factors in multiple spatialscales Ann Limnol Int J Limnol 2011 47 S91ndashS105 [CrossRef]

39 Jacobsen D Cressa C Mathooko JM Dudgeon D Macroinvertebrates Composition life histories andproduction In Aquatic Ecosystems Tropical Stream Ecology Dudgeon D Ed Elsevier Science London UK2008 pp 65ndash105

40 Hoang DH Bae YJ Aquatic insect diversity in a tropical Vietnamese stream in comparison with that in atemperate Korean stream Limnology 2006 7 45ndash55 [CrossRef]

41 Cao Y Williams DD Williams NE How important rare species in aquatic community ecology andbioassessment Limnol Oceanogr 1998 43 1403ndash1409 [CrossRef]

42 Nijboer RC Schmidt-Kloiber A The effect of excluding taxa with low abundances or taxa with smalldistribution ranges on ecological assessment Hydrobiologia 2004 516 347ndash363 [CrossRef]

43 Braccia A Voshell JR Environmental factors accounting for benthic macroinvertebrate assemblagestructure at the sample scale in streams subjected to a gradient of cattle grazing Hydrobiologia 2006 57355ndash73 [CrossRef]

44 Soininen J Paavola R Muotka T Benthic diatom communities in boreal streams Community structure inrelation to environmental and spatial gradients Ecography 2004 27 330ndash342 [CrossRef]

45 Mikulyuk A Sharma S Egeren SV Erdmann E Nault ME Hauxwell J The relative role ofenvironmental spatial and land-use patterns in explaining aquatic macrophyte community compositionCan J Fish Aquat Sci 2011 68 1778ndash1789 [CrossRef]

46 Stomp M Huisman J Mittelbach GG Litchman E Klausmeier CA Large-scale biodiversity patterns infreshwater phytoplankton Ecology 2011 92 2096ndash2107 [CrossRef] [PubMed]

47 Rodrigues AM Quintino V Sampaio L Freitas R Neves R Benthic biodiversity patterns in Ria deAveiro Western Portugal Environmental-biological relationships Estuar Coast Shelf Sci 2011 95 338ndash348[CrossRef]

48 Waite IR Carpenter KD Associations among fish assemblage structure and environmental variables inWillamette Basin streams Oregon Trans Am Fish Soc 2000 129 754ndash770 [CrossRef]

49 Vannote RL Minshall GW Cummins KW Sedell JR Cushing CE The river continuum conceptCan J Fish Aquat Sci 1980 37 130ndash137 [CrossRef]

50 Beauchard O Gagneur J Brosse S Macroinvertebrate richness patterns in North African streamsJ Biogeogr 2003 30 1821ndash1833 [CrossRef]

51 Pan Y Hill BH Husby P Hall RK Kaufmann PR Relationships between environmental variables andbenthic diatom assemblages in California Central Valley streams (USA) Hydrobiologia 2006 561 119ndash130[CrossRef]

52 Harding JS Young RG Hayes JW Shearer KA Stark JD Changes in agricultural intensity and riverhealth along ariver continuum Freshw Biol 1999 42 345ndash357 [CrossRef]

53 Boyero L Bosch J The effect of riffle-scale environmental variability on macroinvertebrate assemblages ina tropical stream Hydrobiologia 2004 524 125ndash132 [CrossRef]

54 Potapova MG Charles DF Benthic diatoms in USA rivers Distributions along spatial and environmentalgradients J Biogeogr 2002 29 167ndash187 [CrossRef]

55 Halwas K Church M Channel units in small high gradient streams on Vancouver Island British ColumbiaGeomorphology 2002 43 243ndash256 [CrossRef]

56 Jun Y-C Kim N-Y Kwon S-J Han S-C Hwang I-C Park J-H Won D-H Byun M-S Kong H-YLee J-E et al Effects of land use on benthic macroinvertebrate communities Comparison of two mountainstreams in Korea Ann Limnol Int J Limnol 2011 47 S35ndashS49 [CrossRef]

57 Parsons M Norris RH The effect of habitat-specific sampling on biological assessment of water qualityusing a predictive model Freshw Biol 1996 36 416ndash434 [CrossRef]

58 Gerth WJ Herlihy AT Effect of sampling different habitat types in regional macroinvertebratebioassessment surveys J N Am Benthol Soc 2006 25 501ndash512 [CrossRef]

Water 2016 8 27 20 of 20

59 Gilles CL Hose GC Turak E What do qualitative rapid assessment collections of macroinvertebratesrepresent A comparison with extensive quantitative sampling Environ Monit Assess 2009 149 99ndash112[CrossRef] [PubMed]

60 Pashkevich A Pavluk T de Vaate AB Efficiency of a standardized artificial substrate for biologicalmonitoring of river water quality Environ Monit Assess 1996 40 143ndash156 [CrossRef] [PubMed]

61 Saliu JK Ovuorie UR The artificial substrate preference of invertebrates in Ogbe Creek Lagos NigeriaLife Sci J 2007 4 77ndash81

62 Di Sabatino A Cristiano G Pinna M Lombardo P Miccoli FP Marini G Vignini P Cicolani BStructure functional organization and biological traits of macroinvertebrate assemblages from leaf-bags andbenthic samples in a third-order stream of Central Apennines (Italy) Ecol Indic 2014 46 84ndash91 [CrossRef]

63 Vlek HE Šporka F Krno I Influence of macroinvertebrate sample size on bioassessment of streamsHydrobiologia 2006 566 523ndash542 [CrossRef]

64 Carter JL Resh VH After site selection and before data analysis Sampling sorting and laboratoryprocedures used in stream benthic macroinvertebrate monitoring programs by USA state agencies J N AmBenthol Soc 2001 20 658ndash682 [CrossRef]

65 Metzeling L Miller J Evaluation of the sample size used for the rapid bioassessment of rivers usingmacroinvertebrates Hydrobiologia 2001 444 159ndash170 [CrossRef]

66 Kim AR Oh MW Kong DS The influence of sample size on environmental assessment using benthicmacroinvertebrates J Korean Soc Water Environ 2013 29 790ndash798

67 Pinna M Marini G Mancinelli G Basset A Influence of sampling effort on ecological descriptors andindicators in perturbed and unperturbed conditions A study case using benthic macroinvertebrates inMediterranean transitional waters Ecol Indic 2014 37 27ndash39 [CrossRef]

68 Vinson MR Hawkins CP Effects of sampling area and subsampling procedure on comparisons of taxarichness among streams J N Am Benthol Soc 1996 15 392ndash399 [CrossRef]

69 Marini G Pinna M Basset A Mancinelli G Estimation of benthic macroinvertebrate taxonomic diversityTesting the role of sampling effort in a Mediterranean transitional water ecosystem Transit Waters Bull2013 7 28ndash40

70 Buss DF Borges EL Application of rapid bioassessment protocols (RBP) for benthic macroinvertebratesin Brazil Comparison between sampling techniques and mesh sizes Neotrop Entomol 2008 37 288ndash295[CrossRef] [PubMed]

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