Limnologica 32, 54-65 (2002) © Urban & FischerVerlag http://www.urbanfTscher.de/journa[s/Hm no LIMNOLOGICA

Impact of Wastewater Effluent on the Diatom Assemblages Structure of a Brackish Small Stream: Oued Hassar (Morocco)

Brahim Fawzi 1., IV]ohamed Loudiki 2, Said Oubraim 1, Brahim Sabour 1, Mohamed Chlaida 1

Facult~ des Sciences Ben M'sik, Laboratoire d'Ecologie et d'Environnement, Casablanca, Morocco ; 2 Facult6 des Sciences Semlalia, Laboratoire d'Algologie, Marrakech, Morocco

Received: April 4, 2001 • Accepted: December 5, 2001

Abstract

The impact of the wastewater input of M6diouna agglomeration (southeastern area of Casablanca) on the diatom flora and water quality of Oued Hassar stream (Morocco) was studied from July 1997 to August 1998. This wastewater effluent, which was highly loaded with ammonia, orthophosphates and organic matters, had disturbed the diatom assemblages structure and water quality of this stream. The study of the epilithic algal assemblages revealed the presence of 130 taxa of diatoms, 21 of which, according to the available literature, were recorded for the first time in the Moroc- can inland waters. Almost all the latter taxa are mesohalobic or oligohalobic-indifferent. Nitzschia inconspicua GRUN. was the most abundant species (47.7%) and grows particularly at the source of the stream. Navicula subminuscula MANGUIN, Nitzschia capitellata HUST. and Nitzschia desertorum HUST. have their dominance in the highly polluted zones, especial- ly downstream the wastewater input.

Key words: Stream - brackish water - pollution - diatoms - principal component analysis

Introduction

There have been relatively few surveys on diatoms from inland waters in Morocco (MAIFFI 1988). The regions which were examined for diatoms included many lakes in the Moyen-Atlas Mountains (GAYRAL 1954), the Ten- sift River with its tributaries (MAIFFI 1988; CAZAUBON & BADRI 1994) and some other water bodies in the region of Marrakech (MA~Fn & DARLEY 1983; ESSINI 1989).

So far, no surveys have been published about diatoms in inland waters in the area of Casablanca, an area with many environmental problems related to the anthro- pogenic activities. The latter caused many alterations of the biological communities and the water quality of the aquatic system. In this paper, the effects of the municipal

wastewater effluent of Mddiouna agglomeration on di- atom assemblages and water quality of Oued Hassar stream were investigated.

Material and Methods

The study area is located on the Oued Mellah basin. This region has a Mediterranean semi-arid climate. Temperatures range between 25 and 30 °C in summer and between 12 and 19 °C in winter. The mean annual precipitation is very irregular (148.5-992 mm for the 1968-1998 period).

Oued Hassar, a canalized stream with 26 km in length (Fig. 1), is situated on the valley of Oued Mellah River.

*Corresponding author: Dr. Brahim Fawzi, Facult~ des Sciences Ben M'sik, Laboratoire d'Ecologie et d'Environment, B.R 7955, Casablanca, Maroc.; Phone: +212227046 71/72, Fax: +212227046 75, e-mail: fawzi@lycos.com

0075-9511/02/32/01-54 $15.00/0 Limnologica (2002) 32, 54-65

Impact of wastewater effluent 55

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The main source of this stream (station A) is situated 3 km Northeast of M6diouna agglomeration (155 m a.s.1.). Along the Oued Hassar stream, five other sam- pling stations were set up (B, C, D, E and F), in relation to the different degrees of water pollution. Station D be- longs to Oued Mouileh stream, which is the unique trib- utary of Oued Hassar.

The wastewater effluent from M6diouna entered the stream between station A (Oued Hassar's source) and station B. The inflow from this effluent was very differ- ent, the values ranged from 0 to17.6 cm 3 • s -1. Before reaching the station C, the Oued Hassar stream crossed a swampy zone with an abundant vegetation, particularly rich with rushes (Juncus spp.).

Limnologica (2002) 32, 54-65

56 B. Fawzi et al.

From July 1997 to August 1998, water samples and diatoms .were collected monthly from the six sampling stations along Oued Hassar stream (Fig. 1). Diatoms were sampled from the upper surfaces of stones re- moved from the bed stream (CAZAUBON & LOUDIKI 1986). Water temperature, pH, flow and conductivity were measured at each sampling site. The analysis of the other physico-chemical parameters (nitrate, ammonia, nitrite, BOD 5, orthophosphate, chloride, sulphate, calci- um, magnesium, alkalinity, silica, suspended matter) was done in the laboratory according to RODIER (1984) and normes of AFNOR (1994). Chlorophyll a was mea- sured on the epilithic flora after removing silts and fila- mentous algae.

Diatom frustules were cleared from organic matter using H202 (110 V). 1 ml aliquot of the cleaned diatom material from each sample was dried and mounted in Naphrax. At least 400 frustules were counted from each sample to determine the relative abundance of each taxon (COSTE 1978).

The following references were used for the taxonomi- cal determination of species: PATRICK 8Z; REIMER (1966-1975), GERMAIN (1981), RICARD (1987) and KRAMMER ~; LANGE-B ERTALOT (19 8 6-19 91 ).

Results and Discussion

Physico-chemical characteristics The analysis of the physico-chemical data of the Oued Hassar stream is given in Table 1. The main characteris- tics can be summarized as follows: pH: The pH value became more alkaline from the Oued Hassar source to downstream. Its mean values ranged between 7.55 (station A) and 8.42 (station F). Conductivity and flow rate: The highest mean conduc- tivity values were observed at station D (Oued Mouileh stream, 6819 ~tS • cm ~) and at station A (Oued Hassar stream, 5679 ~tS • cm-1). Along the Oued Hassar stream, the conductivity decreased ever more from the source towards downstream stations. The conductivity was minimal at station E (3804 ~S • cm 1), at station F it in- creased slightly (4256 ~S -cm 1). Simultaneously with the diminution of the conductivity an increase of the flow rate could be observed• At station E the flow rate was 9fold higher than at station A. Ionic strength: Chloride, sulphate, calcium and magne- sium mean concentrations evolved in the same way as conductivity did. The highest mean concentrations were noted at stations A and D, respectively. The concentra- tions decreased from the source of Oued Hassar to downstream. The mean concentration for chloride ranged from 7331 mg • 1 1 (station D) to 3810.5 mg • 1 -L (station E), for sulphate from 177 mg• 1-1 (station D) to 108 rag. 1 -~ (station E) and for calcium from 97.2 rag. 1-1

(station D) to 74.2 mg • 1 -I (station E); in contrast, the mean concentrations for magnesium varied between 663 mg. 11 (station A) and 433 rag. 1-1 (station F). Silica: The maximal mean concentration was recorded at station D of Oued Mouileh stream (11.8 mg • 1-~). In Oued Hassar stations, the silica mean concentrations ranged between 9.7 mg. 1-1 at station B and 8.6 rag. 1-1 at station E Alkalinity: The highest mean concentrations in UCO 3- were recorded at stations B (232 mg • 1 1) and D (262 mg • 1-1), whereas the source of Oued Hassar showed the minimal value (172.5 rag. 1-1). Suspended matters (S.M.): In contrast to the ionic strength, the lowest mean amounts of suspended matters were recorded at stations A and D (8.8 and 11.6 mg• 1 -~, respectively), while the highest amount was noted at sta- tion F (79.7 mg • 1-1). The elevated values of suspended matters which were recorded at station B (54.7 _ 33.3 mg • 1-1) and brought by the wastewater effluent of Md- diouna, decreased considerably after the passage of water through the swampy zone (station C: 16.1 _ 8.1 mg • 1-1). Downstream, at station F, the maximal values were essentially caused by the washing of vegetable products (potatos, carrots). Biological oxygen demand: Mean values of BOD5 ranged between 4.8 mg 02 • 1 -~ at station A and 96.6 mg 02. kl at station B. The latter station was also most load- ed in organic matter. The minimal value recorded at this station during the period of survey was 35.5 mg 02 • 1-1. Downstream, the mean values of BOD5 decreased con- siderably after the passage of water through the swampy zone to such an extent that a decline from 96.6 mg 02-1-1 (station B) to 6.7 mg 02 • 1-1 (station C) could be ob- served. Orthophosphate and inorganic nitrogen: Ammonia and orthophosphate showed a similar pattern as the BODs-values. The mean values for both parameters in- creased considerably at station B. The mean values for ammonia ranged between 0.02 mg • 1-1 (station D) and 7.6 mg • 1-1 (station B) and for orthophosphate between 0.25 rag. 1 1 (station A) and 1.92 mg. 1-1 (station B). The passage of water through the swampy zone induces a significant decrease of ammonia and orthophosphate mean concentrations at station C (0.5 mg• 1 -I and 0.73 mg • 1-1, respectively). The important values of ni- trites recorded at station C (1.77 mg• 1-1), could be as- signed to the incomplete oxidization of the high amounts of ammonia recorded at station B. Nitrate concentrations were very important at the source of Oued Hassar (7.89 mg • 1 ~), then they decreased significantly, show- ing the lowest mean values at station B (2.46 mg • 1-1). Downstream, nitrate concentrations increased progres- sively and reached 4.55 mg • 1-1 at station F.

Station D has the weakest quantities of nitrates (0.01 mg • 1-1), nitrites (0.02 mg-1-1) and ammonia (0.02 mg. 1-1).

Limnologica (2002) 32, 54-65

Impact of wastewater effluent 57

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Limnol0gica (2002) 32, 54-65

58 B. Fawzi et al.

Multivariate analysis

A principal component analysis (PCA) was performed on the physico-chemical data set to classify different samples (84) according to the 16 environmental vari- ables measured (Fig. 2). The first two components ac- counted for 46.3% of the variance. The first axis (31.15% of the variance) set conductivity (Con&), chlo- ride (C1-), magnesium (Mg2+), calcium (Ca 2+) and sul- phate (SO~ 2-) against the flow. It could be interpreted as an axis indicating ionic strength (salinity). The second axis ( 15.15 % of the variance) was determined by biolog-

ical oxygen demand (BODs), orthophosphates (PO4 3-) and ammonia (NH4 +) against nitrate (NO~-). This axis in- dicates that the organic pollution was generated princi- pally by the wastewater input.

The projection of the samples from different stations (July 1997 to August 1998) on the factorial plan 1 x 2 (Fig. 2) shows the spatio-temporal changes of the physi- cal and chemical conditions at the different stations. From the position of the samples is obvious that the en- vironmental variations did not present a straight relation with seasonality. Nevertheless, the above position demonstrates clearly the changes affecting water quality

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Limnologica (2002) 32, 54-65

along the length of Oued Hassar stream. In principle, 4 groups were individualized on the factorial plan 1 x 2: the first and second group gathered samples from sta- tions A and D with a high ionic concentration. The third group gathered samples from station B which have an important organic pollution load. This station revealed a very important amplitude of variation in regard to ionic strength and organic pollution. The fourth group, situat- ed on the left side of the factorial plan, brought together samples from stations C, E and F. These stations were characterized by a relatively low ionic strength and or- ganic pollution. Fig. 3 summarizes the changes of water salinity and organic pollution load along the length of Oued Hassar stream.

Impact of wastewater effluent 59

Oued Hassar is a salinized stream characterized by high amounts of chlorides and magnesium. The same characteristics could be observed in many other aquatic systems of the C6tiers of Casablanca Basin, for instance the Oued Mellah Lake (SABOUR et al. 2000) and the Oued Nfifikh River (KHATAMI 1992). The salinity origi- nated essentially from the Permo-triasique saliferous sedimentary layers in the studied area (KHATAMI 1992). All of these waters could be assigned as ~- to a-meso- halobic according to the halobion system of HUSTEDT (1957). Besides this fact, these waters showed a high total alkalinity and pH values from weakly acidic to greatly alkali from the source to downstream. The impact of organic pollution generated by the wastewater

2 Stations mema coordinates on the first axis (C1)

D

W

z o n e

Rclativc distance from the source v']

• 2 .J

3 b Stations mean coordinates on the second a:ds (C2)

~ F " o 1 =cd w i:t: e

B Fig. 3. Changes of water salinity (a) and organic pollution (b) (coded by the average coordinates of stations on the two main axes of the PCA) along Oued Hassar stream. W = Wastewater input.

Limnologica (2002) 32, 54-65

60 B. Fawzi et al.

effluent of M6diouna agglomeration essentially resulted in the high concentrations of ammonia, orthophosphates and organic matters detected at station B. At this level, the water quality was highly damaged by sickening odours and colourful water. Downstream station B, the water quality became less affected. The swampy zone - between stations B and C - seems to play the most im- portant role in the restoration of Oued Hassar water quality.

Composition of the diatom flora

A total of 130 different taxa (Table 2) was counted in the 84 samples of the epilithic diatoms collected from the six stations. The genera Navicula and Nitzschia repre- sented 45% of all taxa. The increase of the number of taxa belonging to these two genera can be explained by the elevated amounts of phosphates in the eutrophic sec- tions of the stream (see also ROUND 1993). ESSINI (1987) and MAIFFI (1988), who were working on some eutroph- ic water bodies in the region of Marrakech, indicated similar proportions (45% and 50%, respectively).

Taxa which are typical for less mineralised or acidic water bodies - for instance Frustulia and Pinnularia - were rarely represented. Only one species of the genus Pinnularia (Pinnularia appendiculata) was growing at station C in May 1998 with a relative abundance of 20%. The genus Frustulia was also represented by one taxon, it was found at station F in December 1997. Frustulia sp. could not be determined up to the species level because of the limited number of frustules.

According to the available literature, 21 of the taxa found in this study were reported for the first time for Moroccan inland waters. However, only two of these new taxa were found abundantly: Achnanthes kolbei shows the maximal abundance at station D in December 1997 (11%), while Navicula perminuta amounted to 58% at station C in the same period. Campyloneis gre- viIIei, never reported for Moroccan inland waters before and described by RICARD (1987) in the "Atlas de phyto- plancton marin" as the only species of the genus Campy- loneis, was found both at station D and E.

Two commonly found diatoms which were not identi- fied up to the species level were Cymbella sp. and Gom- phonema sp. The first species (Cymbella sp.) was found at stations C and E in May 1998 with abundances of 20% and 20.6%, respectively. It had a similar shape as Cym- bella brehmii Hvsr., but more striae (15-18/10 ~m). The second species, Gomphonema sp., was found especially at station C. It was similar in size to Gomphonema bipunctatum KRASSKE with less striae (9-10/10 gin), but not in shape (capitate linear - elliptic valve).

Most of the identified taxa were mesohalobic or oligohalobic indifferent. The mesohalobic and oligo- halobic-indifferent groups were represented by 49 and

38 taxa, respectively, whereas the polyhalobic group was only represented by one species [Amphora coffeae- formis (As.) K~TZ.]. The halophilic group included 9 species, while the halophobic diatoms were represent- ed only by one taxon (Nitzschia gracilis HANTZSCH).

The list of diatom taxa registered in the naturally salinized Oued Hassar stream revealed a great similarity with the diatoms of some salt-polluted rivers in Ger- many, e.g. salt-loaded sites of the rivers Werra and Ul- ster (MEINEL & BARLAS 1987; HOFMANN 1997) and Ur- bach and Helbe (BussE et al. 1999).

The structure of the diatom flora in relation to water quality

In regard to the number of taxa and its frequency, station C has with 79 taxa (60.8% of the total number) the rich- est diatom flora, whereas station B showed the lowest number of diatoms (40 taxa). Actually, at this station many species seem to originate from station A diatom assemblages (e.g. Achnanthes inflata, Denticula kiitzingii, Navicula capitata var. hungarica, etc.), this has a great influence on the diversity at station B. How- ever, this ascertainment could not be confirmed since no difference was made between alive and dead cells in our material sampled (see ROUND 1993).

Station A, which was the less polluted station, shows a relatively low diversity (59 taxa). This station was im- pacted by intermittent physical and chemical distur- bances which were caused by the anthropogenic activi- ties (use of detergents in laundering, perturbation of the stream bed). However, the physical and chemical analy- ses did not enlighten the irregular impact as the diatom assemblages did.

Among all stations, D was the most salt-loaded one. Although it showed very low chlorophyll a contents (5 mg • rn 2, caused by the weak amounts of nutrients, es- pecially nitrogen), it represented a relatively diversified diatom assemblage (66 taxa out of the 130 taxa found in the study area).

The influence of the geology of the catchment area (Permo-triasique saliferous sedimentary layers) on the composition of the diatom flora was very obvious. All dominant taxa were halophilic (12%), oligohalobic-in- different (42.5%), mesohalobic (42.5%) or polyhalobic (3%). The halobion index calculated according to ZIE- MANN (1970) showed that the index values ranged from 17.4 at station B (September 1997) to 77.9 at station E (August 1997).

The most abundant diatom was Nitzschia inconspicua Gt~UN. It particularly dominated in the source of the stream and seemed to escape the high level of pollution (Fig. 4a). N. inconspicua was mostly abundant at station A (47.67%) and decreased considerably at station B (8.74%), then it became again progressively more abun-

Limnologica (2002) 32, 54-65

Impact of wastewater effluent

Table 2. Diatom taxa recorded at the sampling stations of Oued Hassar stream with their corresponding average abundances (%).

61

N ° Taxa Station

A B C D E F

1 Achnanthes delicatLl/a (KOTZ.) GRUN. + 2.03 0.60 0,46 0,54 2 Achnanthes hungarica GRUN. + 3 Achnanthes inflata (KOTz.) GRUN, 1.86 O. 13 + 4 Achnanthes kolbei HUST.* 4.22 0.23 2.00 2.20 0.38 + 5 Achnanthes lanceolata (BREB.) GRUN, + + 3.06 0.79 0.76 + 6 Achnanthes minutissima KOTZ. 9.02 2.45 1.12 12.73 6.48 0.35 7 Amphora Iibyca FUR. 0.63 0.31 0.36 0.08 + 8 Amphora coffeiformis (AG,) KOTz. 0.80 6.12 0.89 8.37 0.74 0.60 9 Amphora inariensis KRAMMER* 0.25 +

I 0 Amphora montana KRASSKE + 11 Amphorapediculus(KOTz.) GRUN. 0.25 0.11 6.51 0.58 0.70 1,91 12 Amphora sabiniana REIM.* + 0.70 + + 13 Amphora veneta KOTZ. + 0.76 4.04 0,48 0.85 0.42 14 Amphora ventricosa GREG. + + 0.63 O. 18 0.94 15 Amphora sp. + 16 Bacillaria paradoxa GMELIN + 17 Brachysira aponina KOTZ.* + 0.27 18 Caloneis macedonica HUST. ÷ 19 Campylodiscus bicostatus W, SMITH ÷ ÷ 20 Campyloneisgrevillei(W. SMITH) GRUN.* + 0.26 21 Chaetoceros muelleri LEMMERMANN + 22 Cocconeis disculus SCHUMANN O. 16 23 Cocconeis pediculus EHR. + 24 Cocconeisplacentula EHR. 0.53 0.82 9,02 7.07 3.81 10.70 25 Cocconeis pseudomarginata GREG,* 26 Cyclotella meneghiniana KOTZ. + 0.25 + 0.09 + 27 Cydotella oce/lata PANTOCSEK O, 17 28 Cydotella pseudostelligera HUST. + 0.09 29 Cydotella sp.~ + 30 Cymbella affinis KOTZ. + 31 Cymbella amphicephala NAEGELI + 32 Cymbel/a microcephala GRUN. 1.08 O. 16 + 1,13 0.29 33 Cymbella pus/Ha GRUN. ÷ + 0,61 34 Cymbel/a Sinuata GREG. 0.42 + + 0.20 35 Cymbellasp.~ (brehmfiHusT.?) 1.47 1.44 36 Penticula kEitzingii GRUN. 7.31 1.62 O. 17 O. 13 + 37 Diploneis pseudovalis HUST.* + 0.22 + 0,36 0.09 + 38 Diploneis smithii (BR~B.) CLEME vat. di/atata (PERAGALLO) TERRY + + + 39 Entomoneis paludosa (W. SMITH) REIMER var, subsalina +

(CLEVE) KRAMMER 40 Ephithemia sp. + 41 FragilariabrevistHataGRUN. + 1.26 10.07 1.21 5,87 3.16 42 Fragilaria capucina DESMAZIERES var. graci/is (OESTRUP) HUSl,* ÷ 43 Fragilaria construens (EHR,) GRUN. var. venter(EHR.) GRON. 0.42 0.88 0.29 0.97 + 44 Fragilaria fasdculata (AG.) LANGE-BERTALOT 0.50 0.37 O. 12 3,23 0.78 + 45 Fragilaria pulchella (RALFS ex KOTZ.) LANGE-BERTALOT 0.59 0.36 + 0.24 46 Fragilaria ulna (NITZSCH.) LANGE-BERTALOT 0.49 O. 19 0.34 + 0.09 + 47 Fragilaria ulna var. acus (KO~z.) LANGE-BERTALOT 1.72 O. 11 48 Frustulia sp.~ + 49 Gomphonema sp, 2.40 0.70 50 Gomphonema angustatum (KOTz.) RABH. ÷ ÷ + 51 domphonema angustum AG. + + O. 59 0.21 + 52 6omphonema gracile EHR. + + + 53 domphonema parvu/um (KOTZ.) KOTZ. 2.67 2,64 1.95 0.68 2.99 1.17

Limnologica (2002) 32, 54-65

62 B. Fawzi et al.

Table 2. (Continued).

N ° Taxa Station

A B C D E F

54 Gyrosigma accuminatum (KOTz.) RABH. + 55 @rosigma macrum (W. SMITH) GRIFFITH & HENFREY 56 Hantzschiaamphioxis(EmR.) GRUN. 0.13 57 Melosira granulata (EHR.) RALFS var. angustissima O. MOLLER 0.26 58 Navicu/a capitata EHR. var. hungarica (GRuN.) ROSS. 2.54 0.85 59 Navicu/a car/EHR. 60 Navicu/a cincta (EHR,) RALFS +

61 Navicu/a cohnii (HiLSE) LANGE-BERTALOT* 62 Navicula cryptotenella LANGE-BERTALOT 63 Navicu/a duerrenbergiana HUST. 64 Navicu/a eidrigiana CARTER* 65 Navicula erifuga LANGE-BERTALOT 66 Navicu/a gregaria DONKIN 67 Navicula halophila (GRuN.) A, CLEVE 0.32 + 68 Navkula ignota KRASSKE var. acceptata (HuST.) LANGE-BERTALOT* 69 Navku/a minuscula GRUN. muYalis LANGE-BERTALOT 70 Navicu/a mutica KOTZ. var. ventricosa (KOTz.) CLEVE & GRUN. 71 NaviculaperminutaGRUN.* 0.16 72 Navicula phyllepta KOTZ. 0.26 0.50 73 Navicula pupula KOTZ. 74 Navicula pygmea KOTZ. + 75 Navkula radiosa KOTZ. 76 Navicu/a recens (LANGE-BERTALOT) LANGE-BERTALOT 0.29 1.78 77 Navicu/a sa/inarum GRUN. 78 Navkula saprophila LANGE-BERTALOT + 79 Navicula schroeterii MEISTER 80 Navicula spicula (HICKIE) CLEVE + 81 Navkula subminuscula MANGUIN 5.77 25.24 82 Navicula subrotundata HUST.* 83 Nav/cula tenelloides HUST. 84 Navicula tenera HUST. 85 Navicula veneta KOTZ. 3.85 3.11 86 Navicula viridula (KOTZ.) EHR. var. rostellata (KOTz.) A. CLEVE + 87 Navicula sp, 88 Navicula sp< 89 Navicu/a sp. 3 90 Nitzschia amphibia GRUN. + 91 Nitzschia aurariae CHOLNOKY + 92 Nitzschb ca~ida GRUN. 93 Nitzschb capitellata MUST. 0.96 16.20 94 Nitzschb c/aus# MANTZSCH 95 Nitzschia compressa (BAILEY) BOYER* 96 Nitzschia compressa (BAILEY) BOYER var. vexans (GRuN,)

LANGE-BERTALOT* 97 Nitzschia constricta (KOTz,) RALFS 98 Nitzschia desertorum HUST. 1.41 22,98 99 Nitzschia dissipata (KOTZ.) GRUN.

100 Nitzsch/a dubiaW. SMITH 101 Nitzschia elegantula G RUN. 0.80 + 102 Nitzschia frustulum (KOTz.) GRUN. vat. frustulum 103 Nitzschia gracilis HANTZSCH 104 Nitzschia hungarica GRUN. + 0.31 105 Nitzschia inconspicua GRUN. 47.67 8.74 106 Nitzschia/aevis H UST.*

0.32

0.89 +

0.56 + + + + +

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9.01 0.27 +

4.50

5.85 +

5.93

0.47

6.89

+ +

+ + +

+ +

+ 0,11

+ +

12.29

+ 0,09 + +

0.29

1.92 0,90 0.70

0.45 0,12 +

+ 0.19 +

0.25 0.16 4.03 0.38 0,28 1.33

+ 0.35

1.85 4,47 1.41 6.45 1.73 4.91

+ 0.08 5.04 3.56 4.15

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24.39 25.90 35.11 +

Limnologica (2002) 32, 54-65

Table 2. (Continued).

Impact of wastewater effluent 63

N ° Taxa Station

A B C D E F

107 Nitzschia levidensis (W. SMITH) GRUN. + 108 Nitzscflia microcephala GRUN. 0.28 + O. 18 + O. 11 109 IVitzscflia palea (KOTz.) W. SMITH 0.87 O. 12 0.93 1.62 0.09 5.92 110 Nitzschia paleacea GRUN. + 111 Nitzschia pseudofonticola HusT. ÷ 112 Nitzschia pusi/la (KOTz.) GRUN, 1.31 113 Nitzschia reversa W. SM,TH + 0.66 114 Nitzschia scalpeliformis GRUN. O. 16 0.08 115 Nitzschia thermaloides HusT.* + 116 Nitzschia triblionella HANTZSCH var. levidensis (W. SMITH) GRUN. 0.09 + 0.09 0.32 117 Nitzscflia valdecostata LANGE-BERTALOT & SIMONSON* + 118 Nitzscflia vermicularis (KOTZ,) HANTZSCH + 119 Opephora o/seniiMOLLER* + 0.33 0.14 0,14 120 Pinnu/aria appendiculata (AGARDH) CLEVE 1.37 121 Pleurosigma salinarum GRUN. + 122 P/eurosiraleavis(EHR.)COMPERE 0.41 0.17 0.68 5.19 123 Rhoicosphenia abbreviata (Ao.) LANGE-BERTALOT O. 13 0.32 0.84 1.43 0.47 0.71 124 Rhopalodia brebissonii KRAMMER* 0.41 125 Stauroneis producta GRUN.* + + 126 5tauroneis smithfi G RUN. 0.14 127 5urrirella brebisonfi KRAMMER & LANGE-BERTALOT + 128 5urrire//a ova~is BR~B. + 129 Surrire//a pesonis PANTOCSEK + 130 Thalassiosira weissflogii(GRuN.) FRYXELL & HASLE +

Total number of taxa 59 40 79 66 58 64

* = Taxa recorded for the first time in Moroccan inland waters; + = present at less than 1%.

dant downstream. The species Denticula kiitzingii, Achnanthes inflata, Fragilaria ulna var. acus and Nitzschia pusilla tended to a higher abundance in the source samples too, whereas they were uncommon or absent at the other stations (Fig. 4b).

In Morocco, Achnanthes inflata was reported by EssI- NI (1987) in Marrakech area and by LE Co~u (1989) in Chella source (Rabat). It occurred together with Denti- cula kiitzingii in [3-mesosaprobic water abundantly, while Fragilaria ulna vat. acus and Nitzschia pusilla dominated under oligosaprobic conditions.

Navicula subminuscula, Nitzschia desertorum and Nitzschia capitellata were mainly abundant at station B (Fig. 4c), downstream the wastewater input, where the water reached polysaprobic or isosaprobric levels. In fact, Navicula subminuscula was reported to be one of the most resistant species to organic pollution (LANGE- BERTALOT 1979; GERMAIN 1981) and to industrial sewage as well (KRAMMER & LAN~E-BERTALOT 1986). Nitzschia capitellata tolerated polluted water until the polysaprobic level (KRAMMER & LANGE-BERTALOT 1986), and also Nitzschia desertorum was recognized as

a species of polluted water (GASSE 1986). It was report- ed by MAIFFI (1988) in the Tensift River (Morocco), downstream of some wastewater inputs.

After Oued Hassar stream crossed the swampy zone, Amphora pediculus, Navicula saprophila, Amphora veneta, Achnanthes delicatula, Achnanthes lanceolata, Gomphonema sp. and Pinnularia appendiculata flour- ished at station C, in particular (Fig. 4d). The composi- tion of the diatom assemblages indicated a relatively im- portant recovery at this level. In this part of the stream, the organic matters were almost completely mineralized. Water became eutrophicated, resulting in the growth of the former species. Such as Amphora pediculus, these species seemed to prefer eutrophic water, slightly loaded with organic matters. The abundance of the three species which are dominant in the polluted water at station B (Navicula subminuscula, Nitzschia desertorum and Nitzschia capitellata), considerably decreased at this station.

At station D, characterized by high amounts of salt and organic matters, and small amounts of nutrients, an important growth of Achnanthes minutissima, Amphora

Limnologica (2002) 32, 54-65

64 B. Fawzi et al.

o/.

:0

0 a

,~iL incottsoicrta rag/l,. 12(

- 8 0

:i;,iM :iii ili; ~M - 40 :L::~

~!iiii

A B C D E

0 '

b

%

A B

[] Nay. subenimtscula 1:1 NiL desertorum • Nit. capitetlata

C D E F

% [] DetT. k#tz#~gii t:l Ach. #Clara [] Fra. ubla (acre')

14, %

7 '

0 e

%

[] Ach. mimaissima ~ - % [] Ach. co, ff'eaefoiw~i.

;iiii.Na 'phy" ,o i!!i

i!ii

i , ,

A B C

A B C D E F

0 Amp. pediculus [ ] Nm,. saprophi/a • Amp. vettela

A B C D E F

0 Nit. palea Cl PN. leavis • Nay. er(fi~g,

:ii~i

~ili'i!! Fig. 4. Changes of the average abundance of the most dominant diatom species at the six sampling stations A-E

cof feaeformis , Nav icu la phy l l ep ta and Fragi lar ia fasc ic - ulata could be observed (Fig. 4e). Among these species, A m p h o r a co f f eae formis showed the highest abundance values at stations D and B, but only when the magne- sium concentration exceeded 600 mg• 1 ~.

In comparison with station C, we remarked an in- crease in the abundance of N a v i c u l a s u b m i n u s c u l a (8.42%), Nav icu la veneta (9.39%) and Ni t z sch ia deser- torum (9.12%) at station E, indicating a little decline in water quality. Downstream, the relatively more impor- tant abundance of Ni t z sch ia p a l e a (5.92%), Pleuros i ra leavis (5.19%), and N a v i c u l a e r i fuga (4.03%) was the

most conspicuous change in the diatom assemblages composition (Fig. 4t).

N i t z s c h i a p a l e a , which was known to be extremely resistant to the organic pollution (LANGE-BERTALOT 1979), presented in our study area a maximum of abun- dance in the oligosaprobic sections of the stream. This species, commonly known as oligohalobic- indifferent ( F o o d 1978), seems to have a different behaviour in re- gard to pollution in highly mineralized water. On the other hand, Nav icu la subminuscuIa , Ni t zsch ia cap#el la- ta and Ni t z sch ia d e s e r t o r u m were important indicators of a high pollution of these waters.

Limnologica (2002) 32, 54-65

Conclusion

The impact of the wastewater effluent of M~diouna on the water quality of the Oued Hassar stream was demon- strated by the physical and chemical characteristics, as well as by the composition of the diatom flora. At station B, downstream the wastewater input, the dominance of Navicula subminuscuIa, Nitzschia capitellata and Nitzschia desertorum, which were very resistant to a high pollution, witnessed this impact. However, Nitzschia palea, commonly known as a polluted water species, seems to avoid high amounts of organic pollu- tion in these salt-loaded waters.

ROUND (1991) stated: "The chemical data that yield obvious distinctions between communities are generally the extreme values of the various factors". In fact, ex- treme values separated principally stations A, B and C. The wastewater effluent of M6diouna had an important impact on the water quality and diatom flora of this stream. This impact was naturally and fortunately re- duced at the swampy zone, leading to an improvement of water quality and, ultimately, to distinct diatom as- semblages. This natural wetland displayed an important role in the self-purification of Oued Hassar water. Nev- ertheless, the wastewater problem should be solved by a sewage treatment plant, which must be established in Mddiouna agglomeration.

Later, more investigations should be undertaken in an effort to improve our knowledge about the diatom as- semblages in such water systems and to ascertain the in- fluence of salinity on the resistance of some diatom species in regard to organic pollution.

References

AFNOR (1994): Recueil des normes fran~aises, eaux, m6th- odes d'essais. 736 pp.

BUSSE, S., JAHN, R. & SCHULZ, C.-J. (1999): Desalinisation of running water: II. Benthic diatom communities: A compara- tive field study on responses to decreasing salinities. Lim- nologica 29: 465-474.

CAZaUBON, A. & BADRI, A. (1994): Influence des variations hy- drodynamiques de l'Oued Tensift (Maroc) sur les peuplements de diatomdes. Ecologia Mediterrranea 22 (1/2): 97-108.

- & LOUDIKI, M. (1986): Micror6partition des algues 6pilithiques sur les cailloux d'un torrent corse, le Rizzan6se. Annals. Limnol. 22: 3-16.

COSTE, M. (1978): Sur l'utilisation des diatomdes benthiques pour l'appr6ciation de la qualit6 biologique des eaux courantes. M6thodologie compar6e et approche ty- pologique. Th. 3 ame cycle. Univ. Besan~on, 143 pp.

EssIN~, A. (1987): Zone d'dpandage des eaux us6es de la ville de Marrakech (Maroc): biotopes aquatiques, peuplements algaux et qualit6 des eaux. Thbse 3 e~ Cycle. Univ. Cadi Ayyad, Marrakech, 181 pp.

FOGED, N. (1987): Diatoms in Eastern Australia. Bibl. Phycol., 243 pp.

Impact of wastewater effluent 65

GASSE, E (1986): East African diatoms. Taxonomy, Ecological distribution. Bibl. Diatomol., 290 pp.

GAYRAL, R (1954): Recherches phytolimnologiques au Maroc. Trav. Institut Scientifique Ch6rifien. S6rie Bot. 4. Th6se Sci. Nat., 312 pp.

G~RMAIN, H. (1981): Flore des diatomdes. Eaux douces et saumfitres. Boub6e et Cie, Paris, 443 pp.

HOFMANN, a. (1997): Diatom communities in the rivers Werra and Ulster (Germany) and their response to reduced salinity. Limnologica 27 (1): 77-84.

HUSTEDT, F. (1957): Die Diatomeenflora des Flugsystems der Weser im Gebiet der Hansestadt Bremen. Abh. Naturw. Ver. Bremen 34: 181-440.

KHATAMI, A. (1992): Hydrologie du sahel de Mohammedia- Benslimane: Etude hydrochimique, incidences des irriga- tions et des apports atmosph6riques sur l'6volution des eaux et des sols. Th~se 3 ~m~ Cycle. Univ. Louis Pasteur, Stras- bourg, 205 pp.

KRAMMER, K. & LANGE-BERTALOT, H. (1986-1991): Stiss- wasserflora von Mitteleuropa. Bacillariophyceae, 2/1: Nav- iculaceae; 2/2: Nitzschiaceae, Epithemiaceae, Surirella- ceae; 2/3: Centrales, Fragilariaceae, Eunotiaceae; 2/4: Achnanthaceae. Gustav Fischer Verlag, Stuttgart.

LANGE-BERTALOT, H. (1979): Pollution tolerance of diatoms as a criterion of water quality estimation. Nova Hedw., Beih. 64: 285-304.

LE COHU, R. (1989): Morphologie des valves et 6volution du cingulum chez Achnanthes inflata (Bacillariophyceae). Annls. Limnol. 25 (1): 39-45.

MAIFFI, M. (1988): La flore algale de l'Oued Tensift. Impact des eaux usdes de la ville de Marrakech (Maroc). Les di- atom6es, indicateurs biologiques de la qualit6 des eaux. Th6se 3 ~rne Cycle, Univ. Paris, 234 pp.

- & DARLEY, J. (1983): La flore algale du bassin de la Menara Marrakech. Bull. Fac. Sc. Marrakech, 2: 215-216.

MEINEL, W. & BARLAS, M. (1987): Biozoenotische und hydro- chemische Bestandsaufnahme der Werra und Ulster. Umweltplanung, Arbeits- und Umweltschutz 58: 1-173.

PATRICK, R. & REIMER, C.W. (1966): The diatoms of the Unit- ed States (exclusive of Alaska and Hawai). Monograph of the Academy of Natural Sciences of Philadelphia 13 (1), 688 pp.

- (1975): The diatoms of the United States. Monograph of the Academy of Natural Sciences of Philadelphia 13 (2), 213 pp.

RICARD, M. (1987): Atlas du phytoplancton marin. Vol. 2 : Diatomophyc6es. CNRS, Paris, 297 pp.

RODIER, J. (1984): L'analyse de l'eau. 7 e 6dition, Dunod, Paris, 1135 pp.

ROUND, F. E. (1991): Epilithic diatoms in acid water streams flowing into the reservoir Llyn Brianne. Diatom Research 6 (1): 137-145.

- (1993): A review and methods for the use of epilithic di- atoms for detecting and monitoring changes in river water quality. HMSO, London, 63 pp.

SABOUR, B., LOUDIKI, M., OUDRA, B., OUBRAIM, S., FAWZI, B., FADLAOUI, S., CHLAIDA, M. & VASCONCELOS, V. (2000): Blooms of Prymnesium parvum N. CARTER (Chrysophyta, Haptophyceae) associated with fish mortalities in a hyper- trophic brackish lake in Morocco. Harmful algae news, IOC-UNESCO 21: 8-9.

ZIEMANN, U. (1970): Zur Galtigkeit des Saprobiensystems in versalzten Binnengew~ssern. Limnologica 7: 279-293.

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