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Kirsten Benkendorff*, Ryan Baring, Tom Stewart and Tanith Ramsdale.
*Author for correspondence, School of Biological Sciences,
Email: [email protected] .au
Ph: 8201 3959; Fax: 8201 3015
IMPACTS OF SAND�DREDGING: O’SULLIVANS�
BEACH�DECEMBER 2009
O’Sullivans Beach intertidal reef in April, 2009 after sand dredged from the O’SullivansBeach Marina was deposited on the adjacent shore.
1 | P a g e
SummaryIn April 2009 sand dredged from the O’Sullivans Beach Marina was dumped on the adjacent
intertidal reef at O’Sullivans Beach. This report documents the outcomes of a monitoring
program to assess any immediate impacts of the sand deposition (May 2009) relative to
control sites, as well as the recovery of intertidal communities six months later (October,
2009). Where possible, comparisons are also made to pre-impact surveys undertaken in
November 2007. Overall there was minimal evidence of any substantial impacts on the
intertidal reefs as a result of sand dumping. Most of the sand had cleared from the intertidal
zone by May 2009 and although some large anoxic patches of sand were observed in the
higher intertidal zone, these had all cleared by October, 2009. Transect surveys of the
percent cover of intertidal habitat revealed a relatively high proportion of bare substrate
and less algal cover in May 2009 relative to November 2007. However, this occurred across
all sites, including controls and had mostly recovered by October 2009, thus indicating
natural seasonal variability. The diversity and abundance of invertebrates from quadrat
surveys was found to vary in both space and time, with the impact sites surveys generally
falling within the range of control sites post-impact. The abundance of molluscs increased
substantially in October relative to May, 2009, most likely as a result of the corresponding
increase in algal cover. Multivariate analyses revealed no significant different in invertebrate
community composition between impact and control sites. The macrofaunal communities
were observed to change significantly over time at all sites. Dispersion also varied between
sites but with no consistent effect over time according to proximity to the sand deposition
(i.e. impact vs. control sites). Surveys for the whelk Dicathais orbita also revealed no
evidence for negative impacts associated with sand accumulation in the shallow subtidal
area subsequent to the dredging. Overall these surveys indicate that intertidal reefs such as
O’Sullivans Beach may be relatively resilient to one-off sand dumping events at the
beginning of Winter. Nevertheless, caution should be taken before extrapolating these
results to other any locations, times or larger scale dredging activities.
2 | P a g e
Contents
Summary .................................................................................................................................................2
Introduction ............................................................................................................................................4
Aims ....................................................................................................................................................6
Methods.................................................................................................................................................. 7
Study sites & surveys ..........................................................................................................................7
Substrate Percent cover& sand depth................................................................................................9
Sand accumulation..............................................................................................................................9
Intertidal gastropod abundance & sessile organism cover ................................................................9
Abundance and size frequency of Dicathais orbita ............................................................................9
Statistical Analyses............................................................................................................................10
Results...................................................................................................................................................10
Video Transect Data..........................................................................................................................10
Sand Accumulation ...........................................................................................................................12
Species Richness ...............................................................................................................................15
Species Diversity ...............................................................................................................................15
Photo Quadrat Abundances and Percent Cover of Sessile Invertebrates ........................................18
Invertebrate Community Composition .............................................................................................21
Dicathais orbita abundance and size ................................................................................................23
Discussion..............................................................................................................................................24
References ............................................................................................................................................26
Appendix ...............................................................................................................................................28
3 | P a g e
IntroductionCoastal marine habitats in South Australia can be essentially divided into soft sediment
habitats (e.g. sandy beaches) and rocky reefs. Distinct ecological communities have evolved
to live in, or on, these vastly different substrata (Benkendorff et al., 2008). In particular,
rocky intertidal shores are highly productive environments with large visible populations of
a range of invertebrates, predominantly molluscs. The hard substratum is coated with a
microbial biofilm that provides a source of food for micrograzers, such as limpets and snails.
In the mid-to-lower intertidal zones the hard substrate also provides suitable attachment
sites for macroalgae and sessile invertebrates, including barnacles, mussels and other filter
feeding organisms. On the other hand, sandy marine habitats often resemble a desert
(Benkendorff et al., 2008). Whilst many invertebrates are adapted to live in the sand, they
are mostly microscopic or burrowing organisms that hide beneath the sand surface.
Consequently, the deposition of sand on rocky reefs is expected to result in detrimental
impacts to rocky shore adapted organisms.
Previous studies on the effects of sedimentation on rocky intertidal and subtidal reefs have
revealed a range of effects due to scour and smothering. These include reduction of light
availability for juvenile plants, interference with the recruitment and survival of algae
(Airoldi and Cinelli, 1997; Littler et al., 1983; Scheil et al., 2006; Yanez et al., 2008), changes
in the zonation patterns (Littler et al., 1983) and species diversity (Huff and Jarett, 2007;
Pulfrich et al., 2003), as well as the unstabilisation of communities (Prathep et al., 2003).
Sand smothering can also interfere with respiration and feeding activity of intertidal
organisms (Airoldi and Hawkins, 2007) and interfere with settlement and recruitment
patterns (Taylor and Littler, 1982; Pineda, 1994). Consequently, if sand persists on rocky
shores, it may lead to long-term shifts in the local ecological communities and ultimately a
reduction in the productivity of the area.
Periodically, sand dredging activities are required along the South Australian coast in order
to maintain boat access in harbours and marinas. For practicality, the excess sand is often
disposed locally at adjoining coastal areas, as off-shore disposal or trucking the sand away
would have significant cost implications. However, these economic costs need to be
weighed up against potential long-term environmental impacts. To date no studies have
investigated the effects of sand dumping on rocky reefs in South Australia. Recently,
community concerns have been raised over the deposition of sand on O’Sullivans Reef, as a
result of dredging the local marina. Personal observations at the site a few weeks after the
dredging event indicate that significant areas of the reef were smothered by sand (Figure 1).
Large sand patches remained in the mid-high intertidal areas extending north of the marina
and beyond the Port Stanvac fence, up towards the Port Stanvac Jetty. However, in well
flushed lower intertidal areas, much of the sand appeared to have dispersed within a couple
of weeks. This indicates that the long-term effects of sand deposition on rocky reefs may
depend on a combination of factors, including the topography of the reef, water movement
and sand dispersal, as well as the scale and frequency of the sand deposition. The recent
dredging event in early 2009 at the O’Sullivans Beach site offers a good opportunity to
4 | P a g e
investigate the short term impacts on local rocky reef communities and some of the factors
that may influence longer-term change.
a) b)
c) d)
Figure 1: The intertidal reef at O’Sullivans Beach pre- (left panels) and post-(right panels)
impact from sand dumping on the rocky shore. Pre-impact photos (a & c) were taken in
November 2007, whereas post-impact photos (b & d) were taken in April 2009. The top
panels (a & b) show the view towards the O’Sullivans Beach Marina which was dredged in
April 2009, where as the lower panels (c & d) show the view toward Port Stanvac, with the
Port Stanvac jetty visible in the background.
5 | P a g e
Assessing impacts to ecological communities can often be complicated by a lack of baseline
data before the impact. Ideally, ecological impacts should be assessed using replicated
studies at the both the impact site and several control sites, both before and after the
impact event (Underwood, 2001). Recent surveys of the shallow subtidal whelk Dicathais
orbita have been undertaken at the impacted O’Sullivans Beach site and potential controls
sites (Noble et al., 2009). As an invertebrate predator, this species can be considered a good
indicator for reef health. Furthermore, in 2007, intertidal surveys were undertaken in the
O’Sullivans Beach & Port Stanvac area for the Adelaide and Mt Lofty Natural Resource
Management Board (Dutton and Benkendorff, 2008). Through the application of
standardised methodology, this data can be used for pre- and post impact comparisons. The
Dutton and Benkendorff (2008) surveys include baseline data at the main impact site, a
more distant impacted site north of the Port Stanvac fence, as well as suitable control sites
at various distances from O’Sullivans Beach (one on the northern side of the Port Stanvac
Jetty, one at Hallett Cove and another at Marino Rocks; refer to Figure 2 and Figure 3).
Useful baseline data from the Dutton and Benkendorff (2008) surveys include standardised
transects for the percent composition of the substrate. Notably, no sand was recorded at
the O’Sullivans Beach main impact site (Figure 1) in the 2007 survey, whilst ~15% of the
habitat was recorded as sand along transects at the Northern impact site at Port Stanvac
(Dutton and Benkendorff, 2008). High species richness and particularly high percent covers
were recorded for turf and foliose algae at O’Sullivans Beach, in comparison to the Port
Stanvac area. Percent cover of sessile invertebrates and mobile gastropods were similar.
By applying standardised methodologies at the previously surveyed impact and control
sites, it should be possible to gain insight into any changes in the rocky reef communities
that have occurred at these sites since the recent sand deposition in early 2009. To fully
assess the scale of impact of the 2009 sand deposition episode, additional sites without
baseline data were implemented in the southern impact zone and a control site south of the
O’Sullivans Beach Marina (Figure 2). All sites were surveyed in May and six months later in
October, 2009, to assess possible recovery. Additional data parameters on sand patches and
topography were recorded at the main impacts sites to gain insight into the nature of sand
persistence on rocky reefs.
Aims
The aim of this project was to assess the impacts of sand deposition at O’Sullivans Beach,
S.A. This was done using previous data and a short term case study of intertidal reefs in the
region. The application of before, after control, impact studies of the rocky reef ecological
communities along the Adelaide Metropolitan coast will provide a model system for future
monitoring programs. Specific objectives are to:
1) Provide a detailed assessment of the percent cover and depth of sand overlying the
rocky substrate along transects at varying distances from the sand deposition site.
2) Characterise the topography where sand has accumulated on the intertidal rocky
reefs.
6 | P a g e
3) Assess the percent cover of sessile intertidal organisms at impact and reference
locations, in comparison to previously collected data.
4) Assess the invertebrate abundance and community composition at control and
impact surveys in May and six months later in October, 2009.
5) Assess the abundance and size frequency distribution of shallow subtidal Dicathais
orbita at one control and one impact site, in comparison to previous data.
Methods
Study sites & surveys
This study focused on the O’Sullivans Beach area (Figure 2), with several reference sites
located at varying distances to the north (Figure 2& 3). In total the study included the main
impact site at O’Sullivans beach, as well as two mild impacted locations (<200m to the north
and South). Nearby control locations were sited < 1km to the north and south side of the
impact zones, both on the other side of large rock groynes preventing indirect sand drift
from the dredges. Two additional sites to the North at Hallett Cove and Marino Rocks were
chosen as secondary control sites located greater than 10 km from the impact zone (Figure
3). Each site was surveyed once in May - June and again in October-November (Table 1). All
intertidal surveys were undertaken in calm weather at low tide. It should be noted that the
first May surveys occurred several weeks after the dredged sand was dumped at O’Sullivans
Beach and subsequent to a major storm event.
Table 1: Sites and sampling dates for the intertidal reef sand dredging impact survey at O’Sullivans
Beach during May and October 2009.
Site GPS Coordinates Sampling Date Tide Height Tide Time
South East May October May October May October
Marino Rocks 35o02’45.6” 138
o30’27.6” 13/05/09 6/11/09 0.61m 0.32 11:40am 1:30pm
Hallett Cove 35o05’06.2’’ 138
o29’31.5” 13/05/09 6/11/09 0.61m 0.32 11:40am 1:30pm
North Control 35o06’28.4” 138
o28’20.0” 14/05/09 5/11/09 0.67m 0.21m 12:06pm 1:00pm
North Impact 35o06’48.8” 138
o28’13.5” 14/05/09 5/11/09 0.67m 0.21m 12:06pm 1:00pm
Main Impact 35o06’57.5” 138
o28’11.2” 12/05/09 2/11/09 0.58m 0.21m 11:12am 11:35am
South Impact 35o07’07.05” 138
o28’06.72” 11/05/09 2/11/09 0.57m 0.21m 10:45am 11:35am
South Control 35o07’16.10” 138
o28’02.36” 29/05/09 22/10/09 0.83m 0.35 12:06pm 1:10pm
7 | P a g e
Figure 2: Intertidal reef survey and whelk sites at O’Sullivans Beach surveyed in May and
October, 2009.
Figure 3: Intertidal reef control sites (>10km from O’Sullivans beach main impact zone)
surveyed in May and October 2009.
8 | P a g e
Substrate Percent cover& sand depth
Ten randomly spaced, 20 m shore-normal line transects were located within each study site
using a 50 m fibreglass tape. To enable rapid survey of substrate types during low tide,
transects were recorded using an Olympus (Model Tough8000) camera. Substrate video
footage was subsequently analysed for percent cover using VLC media player. Substrate
types were recorded in patches greater than 5 cm in length using the line intercept method.
In addition to sand and bare rock, sessile organism cover were recorded along the transects
categorised as; foliose algae, turfing algae, encrusting algae/lichen, seagrass, mussels,
galeolaria crust, mixed community and barnacles according to Dutton and Benkendorff
(2008). The extent of each substrate was recorded in centimetres, summed and divided by
the total length (20m) to obtain the percent cover.
Sand accumulation
The O’Sullivans Beach impact sites were visually assessed for areas of persistent sand
accumulation. 15 sand patches were marked and mapped using GPS. For each sand patch,
the volume of the sand patch was calculated by the surface area X depth (averaged from 10
random depth measurements). The average colour of the sand was recorded by comparison
to numbered paint colour charts in the sandy through grey to black colour scheme, where
darker coloured sand provides an indication of anoxic conditions. The topographical
characteristics of the sand patches were recorded based on distance from the low water
mark and on the average height of the surrounding rock on the seaward side.
Intertidal gastropod abundance & sessile organism cover
At each site, 10 replicate 0.25 m2
quadrats were randomly places in the mid-low intertidal
area and a further 10 in the mid-high intertidal zone. For each quadrat, 5 photographs were
taken using an Olympus digital camera (Model µ1030SW/Tough8000). Quadrats were
divided into quarters, with one photo taken of each quarter, as well as one encompassing
the whole quadrat. Photos were subsequently analysed using imaging software. All visible
mobile fauna were identified and counted. Colonial sessile biota such as Limnoperna pulex
and Galeolaria caespitosa were also assessed for percent cover from the photographs.
Abundance and size frequency of Dicathais orbita
Timed search surveys were undertaken in the shallow subtidal areas for Dicathais orbita at
Marino Rocks and O’Sullivans Beach (main impact site, Table 2). All animals located in a
30min search period were collected then measured using callipers, then returned to the
subtidal area.
Table 2: Sites and sampling dates for the subtidal whelk surveys at O’Sullivans Beach.
Survey Date Location GPS
13-03-08 O’Sullivans Beach Reef - South Control 35 07'15.82"S, 138 28'01.50"E
09-05-09 O’Sullivans Beach Reef - South Control 35 07'15.82"S, 138 28'01.50"E
17-05-09 O’Sullivans Beach Reef - Main Impact Zone 35 07'02.35"S, 138 28'08.32"E
14-11-09 O’Sullivans Beach Reef - Main Impact Zone 35 07'02.35"S, 138 28'08.32"E
9 | P a g e
Statistical Analyses
To determine the diversity and evenness of invertebrate species composition at all sites, three
different diversity indices were calculated (Shannon-Wiener index, Pielou’s evenness and Simpson’s
index) based on the total number of individuals (N) of each taxa (S). The Shannon-Wiener index
identifies greater species diversity with an index number closer to one. Pielou’s index identifies the
equitability of species presence at each site where a larger number indicates less evenness.
Simpson’s index is a measure of ecological diversity with infinite diversity decreasing from zero to
one, indicating dominance of single species (Clarke and Warwick 2001).
Multivariate data on changes in the invertebrate community composition across time and space
were analysed using PRIMER v.6 +PERMANOVA. Square-root transformed, Bray Curtis similarity
(with dummy variable = 1) data were used for the analysis. PERMANOVA was used to investigate
differences in the macrofaunal community among sites and months, using a three-way, nested
design, with Sites (a random factor with 7 levels) nested in Types (a fixed-factor with 2 levels;
impacted versus control) both fully-crossed with Months (a fixed factor with 2 levels; May and
October). PERMANOVA detects significant differences in both community structure and variability.
To separate these, PERMDISP was used to test for significant differences in dispersion (i.e.
variability) among samples and a multidimensional scaling (MDS) plot constructed to investigate
differences in the macrofaunal community structure. Either an increase or decrease in dispersion
can be an indicator of disturbance in marine communities (Anderson et al. 2008).
Results
Video Transect Data
Transect data from the pre-impact sampling period in November 2007 revealed a relatively high
cover of sand at the Northern Impact site (>20%), over 10% sand at Marino and < 2% at Hallet Cove,
but no sand at the Main impact or North Controls in the O’Sullivans Beach/Port Stanvac area (Figure
4a). The percent of bare substrate ranged from <50% at the Main Impact site to 80% at Hallet Cove.
After the sand dumping in May 2009 the video transects revealed a large percent cover of bare
substrate (> 70%) at most sites except the Southern Control site (Figure 4b). In comparison the
percent cover of sand was minimal (< 1%) and only present at the Hallett Cove, Main Impact, South
Impact and South Control sites. In October 2009 the percent cover of bare substrate reduced to
below 70% at all sites, and a low percent cover of sand (< 5%) was recorded at the Marino, Main
Impact, South impact and South Control sites (Figure 4c).
10 | P a g e
November 2007�
(a)
0
10
20
30
40
50
60
70
80
90
100
Pe
rce
nt
cov
er
(%)
sand
bare substrate
Marino Rocks Hallett Cove North Control North Impact Main Impact
(b)
0
10
20
30
40
50
60
70
80
90
100
Pe
rce
nt
Co
ve
r (%
)
May 2009
Sand
Bare Substrate
Marino Rocks Hallett Cove North Control North Impact Main Impact South Impact South Control
100 October 2009 90
80 (c)
Pe
rce
nt
Co
ve
r (%
) 70
Sand
60 Bare Substrate
50
40
30
20
10
0
Marino Hallett Cove North Control North Impact Main Impact South Impact South Control
Figure 4: Mean percent cover of bare substrate and sand cover from video transects at O’Sullivans
Beach impact and controls sites during (a) November 2007 (pre-impact), (b) May 2009 and (c)
October 2009 (post impact).
11 | P a g e
The transect data from the pre-impact November , 2007 surveys is not directly comparable to the
post-impact surveys due finer detail on the algal composition in the 2009 surveys (Figure 5).
Nevertheless, it is clear that higher pre-impact algal cover was found in the Port Stanvac/O’Sullivans
Beach area compared to the more northern sites at Marino and Hallet Cove (Figure 5a). In May,
2009 the total percent cover of flora and sessile fauna dropped at all previously surveyed sites, but
was substantially higher the South Control site, which was strongly influenced by the presence of the
foliose green algae Ulva australis and mixed algal communities (Figure 5b). The percent cover of
mixed algal community was also well represented at the North Control and Main Impact sites.
Compared to May, video transects from October 2009 identified an increase in percent cover of
flora and fauna at all sites except the South Control site which had similar percentages for each
category in both months (Figure 5c). All sites were represented by large percentages of mixed algal
communities, while the North Control and North Impact sites also had large percentages of mixed
invertebrate communities. Encrusting red algae was also well represented at the Main Impact site
with a large contribution to the overall percent cover of flora and fauna for this site (Figure 5c).
Sand Accumulation
Sand accumulation patches on the intertidal reef were only recorded within the Main Impact and
North Impact sites during May, 2009. The sand patches recorded at both sites were limited to the
mid to high tide zones behind rock ledges of > 1 metre in height (Table 3). The overall accumulation
across all sand patches indicated that the mean dimensions of patches were generally large (>1m
width and > 2m length) but with small volumes (< 0.25m3) and appeared to be partially anoxic
according to colouration (Table 3, Figure 6). In October there was no indication of persistent sand
accumulation with zero sand patches were recorded within the Main Impact and North Impact sites.
12 | P a g e
Impact
November 2007�
Perc
ent C
over
(%)
Pe
rce
nt
Co
ve
r (%
) Pe
rcen
t Cov
er (%
)
80
70
60
50
40
(b) 30
20
10
0
80
70
60
50
40
30
20
10
0
0
Marino Hallett Cove North North Main Impact
Rocks Control
May 2009
Mussel
Lichen
Nerita
Mixed Algal /Invertebrate
Mixed Invertebrate Community
Mixed Algal community
Encrusting Green
Foliose Green
Turfing Green
Encrusting Red
Foliose Red
Turfing Red
Foliose Brown
Encrusting Brown
Turfing Brown
Barnacle
Tube Worms
Marino Rocks Hallett Cove North Control North Impact Main Impact South Impact South Control
October 2009
Mussel
Lichen
Mixed Algal /Invertebrate
Mixed Invertebrate Community
Mixed Algal community
Encrusting Green
Foliose Green
Turfing Green
Encrusting Red
Foliose Red
Turfing Red
Foliose Brown
Encrusting Brown
Turfing Brown
Barnacle
Tube Worms
Marino Hallett Cove North Control North Impact Main Impact South Impact South Control
Mussels
Lichen
80
70
Mixed Algae/Invertebrates 60
Foliose Algae (a)
50 Encrusting Algae
40 Turfing Algae
Barnacles 30
Tube worms 20
10
Figure 5: Mean percent cover of flora and sessile fauna from video transects at O’Sullivans Beach
impact and controls sites during (a) November 2007 (pre-impact), (b) May 2009 and (c) October
2009 (post impact).
13 | P a g e
Table 3: Presence of sand accumulation for the Main Impact and North Impact sites recorded during
May 2009. Sand patch colour code for potential oxygen content and quality of sand. N = Normal (1-
3), PA = Partially Anoxic (4-5), HA = Highly Anoxic (6-7), EA = Extremely Anoxic (8).
Site Sand Patch Number GPS position Distance from Low Tide (m) Rock Height (m) Mean Width (m) Mean Depth (m) Length (m) Volume (m3) Sand Patch Colour
Main Impact Zone
Main Impact Zone
Main Impact Zone
Main Impact Zone
Main Impact Zone
Main Impact Zone
Main Impact Zone
Main Impact Zone
Main Impact Zone
Main Impact Zone
1
2
3
4
5
6
7
8
9
10
S35o06’59” E 138
o28’10”
S35o06’58.7” E138
o28’10.6”
S35o06’58.5” E138
o28’11.0”
S35o06’59.0" E138
o28’10.0”
S35o06’58.9” E138
o28’10.4”
S35o06’58.8” E138
o28’10.5”
S 35o06’58.9” E 138
o28’10.3”
S35o06’58.9” E 138
o28’10.5”
S35o06’59.1 E 138
o28’10.4
S 35o07’00.0” E 138
o28’10.2”
21
18
21
23
14
15
12
11
13
13
1 − 2
1 − 2
1 − 2
1 − 2
1 − 2
1 − 2
1 − 2
1 − 2
3
< 1
1.46
1.63
1.30
1.90
0.85
0.65
0.85
0.40
1.80
0.67
0.02
0.02
0.02
0.05
0.02
0.03
0.04
0.06
0.03
0.03
5.00
1.80
2.20
3.40
1.20
0.70
1.54
1.20
2.65
1.80
0.15
0.07
0.05
0.29
0.02
0.01
0.05
0.03
0.13
0.03
3
3
4
4
4
4
4
5
4
4
North Impact Zone
North Impact Zone
North Impact Zone
North Impact Zone
North Impact Zone
1
2
3
4
5
S 35o06’50.1” E 138
o28’13.0”
S 35o06’50.2” E 138
o28’13.2”
S 35o06’50.6” E 138
o28’13.0”
S 35o06’50.7” E 138
o28’12.9”
S 35o06’50.8” E 138
o28’13.2”
15
14
15
13
13
2
3
3
3
1
4.50
3.85
1.25
1.70
1.00
0.06
0.07
0.06
0.06
0.03
2.95
2.18
3.40
1.70
2.90
0.76
0.59
0.26
0.18
0.08
4
4
4
4
4
Mean − − 15.4 − 1.37 0.04 2.31 0.18 3.93
Sand Patch Code
1
2 N
3
4
5 PA
6 HA
7
8 EA
Figure 6: An example of a sand patch showing grey colouration indicative of anoxia in the
sediment dredged from O’Sullivans Beach marina and deposited on the adjacent intertidal reef.
14 | P a g e
Species Richness
Invertebrate species richness recorded from quadrat surveys on the intertidal reefs was highest at
the North Impact and Main Impact sites during May, which was attributed to the large number of
gastropod species (Figure 7a, Appendix 1). Control sites held similar species numbers and mainly
consisted of gastropods, except Marino which had very low species numbers in comparison. The
presence of crustaceans at most sites was represented by two species of barnacles (Chthamalus
antennatus and Chamaesipho tasmanica). In comparison, bivalves and annelids were only
represented by ones species for each taxa (Limnoperna pulex and Galeolaria caespitosa respectively)
(Figure 7a). In October species richness remained highest at the North Impact and Main Impact, as
well as the South Impact site, due to the large number of gastropod species (Figure 7b). However, in
comparison to the May survey the numbers of gastropod species was much lower, while the
presence of bivalves and annelid tubeworms increased overall. In addition, a new species of annelid
tubeworm was recorded at the North Impact and South Control Sites (Pomatoceros taenita) in the
October survey (Figure 7b).
In comparison to the November 2007 pre-impact surveys, species richness was higher at all sites in
the May 2009 surveys, with a maximum of 17 species recorded at two sites within the impact zone
(Table 4). By October 2009, the species richness dropped to similar numbers as recorded in the pre-
impact 2007 surveys, with a maximum of 14 species at O’Sullivans Beach.
Species Diversity
Pre-impact diversity indexes were only available for the North Impact and northern control sites
(Dutton and Benkendorff, 2009). Comparison of the Shannon-Weiner diversity index at the north
impact site showed a decrease in diversity from 1.5 in November 2007 to 0.6 in May 2009m then
recovering to 1.5 in October 2009 (Table 4). A drop in Pielou’s eveness values at the North Impact
site in May 2009 (Table 4) indicates corresponding increase in the eveness between species
abundances immediately post impact. A drop in the diversity and increase in the eveness values was
also observed at the Northern control site in the May 2009 survey in comparison to November 2007,
although the magnitude of change was much smaller than at the main impact site. The diversity and
evenness at the more northern control sites at Hallet Cove and Marino remained relatively constant
over time (Table 4)
The May survey 2009 recorded the highest Shannon-Weiner diversity values at the Main Impact and
Hallett Cove sites (Table 5a), which also had uneven species composition due to the dominance of
the gastropod Nerita atramentosa at both sites and the barnacle Chthamalus antennatus at the
Main Impact site (Appendix 1). Most of the other sites also recorded relatively high species diversity
in May except the North Impact site which had very low Shannon-Weiner diversity values in
comparison (Table 5a). In October 2009, the Hallett Cove, Marino and Main Impact sites decreased
in diversity (Table 5b), while all other sites increased in species diversity when compared to
Shannon-Weiner values recorded in May. The highest Shannon-Weiner diversity values in October
were identified for the South Impact and South Control sites with relatively even species
composition (Table 5b). However, a high Simpson’s Index indicated that there was some species
15 | P a g e
dominance due to the gastropod Siphonaria diamenensis at both the South Impact and South
Control sites and C. antennatus at the South Impact site.
(a)
0
2
4
6
8
10
12
14
16
18
20
Spe
cie
s N
um
be
r
May 2009
Crustacea
Bivalvia
Gastropoda
Annelida
Marino Rocks Hallett Cove North Control North Impact Main Impact South Impact South Control
18
16
(b)
Spe
cie
s N
um
be
r�
Crustacea
14 Bivalvia
12 Gastropoda
October 2009
Marino Hallett Cove North Control North Impact Main Impact South Impact South Control
10 Annelida
8
6
4
2
0
Figure 7: Total species richness recorded from quadrat surveys at the O’Sullivans Beach impact and
control sites during (a) May and (b) October 2009.
16 | P a g e
Table 4: Temporal comparison of the total species richness (S), Shannon-Weiner diversity index (H’)
and Pielou’s evenness (J’) from photoquadrats at the O’Sullivans Beach impact site and northern
controls. The November 2007 surveys were conducted by Dutton and Benkendorff (2008) prior to
the sand impact, where as the May and October 2009 represent post-impact surveys undertaken as
part of this study.
Site November 2007 May 2009 October 2009
S H’ J’ S H’ J’ S H’ J’
Marino 7 1.4 0.6 9 1.3 0.6 6 0.6 0.4
Hallet Cove 12 1.7 0.7 15 1.6 0.6 11 1.2 0.5
North Control 13 1.5 0.6 16 1.0 0.4 12 1.1 0.5
North Impact 14 1.5 0.5 17 0.6 0.2 13 1.4 0.4
Main Impact 14 NA NA 17 1.8 0.6 14 1.1 0.6
Table 5: Diversity Indices for the intertidal reefs survey during (a) May and (b) October 2009.
S = number of taxa; N = total number of individuals.
(a)
Site S N Shannon-Weiner Pielou's evenness Simpson
Marino 9 123 1.300 0.592 0.588
Hallett Cove 15 244 1.622 0.599 0.69
North Control 16 1958 1.028 0.371 0.484
North Impact 17 3584 0.553 0.195 0.244
Main Impact 17 448 1.790 0.632 0.767
South Impact 12 843 1.390 0.559 0.675
South Control 12 407 1.312 0.528 0.615
(b)
Site S N Shannon-Weiner Pielou's evenness Simpson
Marino 6 471 0.627 0.350 0.297
Hallett Cove 11 608 1.199 0.500 0.549
North Control 12 2722 1.140 0.459 0.570
North Impact 13 3208 1.354 0.528 0.648
Main Impact 14 1052 1.125 0.426 0.457
South Impact 14 1526 1.628 0.617 0.751
South Control 11 754 1.488 0.621 0.655
17 | P a g e
Photo Quadrat Abundances and Percent Cover of Sessile Invertebrates
In the May 2009 survey, abundances of all phyla in photo quadrats were highest at the North Impact
and North Control sites and comparatively low at all other sites (< 200 individuals m-2
) (Figure 8a).
The higher abundances of crustaceans at both the North Impact and North Control sites were
attributed to the large numbers of the C. antennatus barnacle (Figure 8b). In comparison, the
abundances of molluscs were highest at the North Impact and North Control sites, but were
comparatively low across all sites (< 110 individuals m-2
) (Figure 8c). In October 2009, the total
abundance of all phyla was greatest at the North Impact, North Control and South Impact sites,
while abundances at all other sites were comparably low (< 300 individuals per m3) (Figure 8a). The
abundances of crustaceans were low at all sites and substantially lower at the North Control, North
Impact and South Impact sites compared to the abundances recorded in the May survey (Figure 8b).
However, the abundances of molluscs increased across all sites in October, and were greatest at the
North Control and North Impact sites (Figure 8c).
Some pre-impact data was available for the percent cover of colonial sessile invertebrates from
Dutton and Benkendorff (2008). However, the percent cover was very low at all sites during the
2007 surveys (Figure 9). In the post-impact surveys of May 2009, percent cover was highest at the
South Control site for the Mytilidae mussels (Figure 9b), while the North Impact and Main Impact
sites were highest for the polychaete worms (Figure 9a). All other sites had very low percent cover of
sessile organisms or they were nonexistent. Colonial sessile invertebrates were recorded at all sites
in October 2009 with the greatest percent cover recorded for Mytilidae mussels at the South Control
site (Figure 9b). In comparison, the percent cover of polychaete worms was comparably low at all
sites (< 15% cover, Figure 9a).
18 | P a g e
All Phyla�
(a)
0
200
400
600
800
1000
1200
Ind
ivid
ual
s m
-2 (+
SD)
May
October
Marino Hallett North North Main South South
Cove Control Impact Impact Impact Control
Crustacea (b)
1000
900
May
October
Ind
ivid
ual
s m
-2 (+
SD)
Ind
ivid
ual
s m
-2 (+
SD)
800
700
600
500
400
300
200
100 (c)
0
Marino Hallett North North Main South South
Cove Control Impact Impact Impact Control
Mollusca 900
May
800
700
600
500
400
300
200
100
0
October
Marino Hallett North North Main South South
Cove Control Impact Impact Impact Control
Figure 8: Abundances of (a) All Phyla (b) Crustacea (c) Molluscs recorded from photo quadrats the
O’Sullivans Beach impact and control sites during May and October 2009.
19 | P a g e
Polychaeta�(a)
0
10
20
30
40
50
60
70
Pe
rce
nt
Co
ve
r m
-2 (
+S
D)
Nov-07
May-09
Oct-09
Marino Hallett North North Main South South
Cove Control Impact Impact Impact Control
(b) Mytilidae�
0
20
40
60
80
100
120
140
160
180
Pe
rce
nt
Co
ve
r m
-2 (
+S
D)
Nov-07
May-09
Oct-09
Marino Hallett North North Main South South
Cove Control Impact Impact Impact Control
Figure 9: Percent cover of sessile colonial invertebrates (a) Galeolaria tube worms and (b) Mytilidae
mussels recorded from photo quadrats the O’Sullivans Beach impact and control sites pre (Nov
2007) and post-impact (May and October 2009) from sand deposition. The pre-impact surveys were
only undertaken at Mario, Hallet cove, the North Control and the main impact sites.
20 | P a g e
Invertebrate Community Composition�
PERMANOVA results showed there was no significant difference based on site Types (impact vs
control). Only small-scale spatial and temporal effects were significant (Table 6). PERMANOVA also
shows that the community structure at all seven sites was significantly different between the two
sampling occasions (Table 7). The MDS plot shows a separation of samples based on sampling
occasions and sites (Figure 10), with replicates tending to clump into groups based on sites and
months, as expected based on the results of the PERMANOVA.
Table 6: PERMANOVA results for the invertebrate community composition on intertidal reefs along
the Fleurieu Peninsula surveyed at two time points after the sand deposition at O’Sullivans Beach
reef. Type shows the effect of grouping for control versus impact sites (refer to Figure 2 & 3). Bold
values for P (permutations-based) indicate significant differences.
Source d.f. SS MS Pseudo-F P (perm)Month 1 103070 103070 15.249 0.0002
Type 1 15380 15380 1.1409 0.2775
Site(Type) 5 67403 13481 7.0279 0.0001
Month x Type 1 9295.7 9295.7 1.3754 0.2618
Month x Site(Type) 5 33794 6758.7 3.5235 0.0001
Residual 266 510230 1918.2
Table 7: PERMANOVA pair-wise tests showing the difference at each site between months (October
v. May, 2009).
Site d.f. T P (perm)
Hallett Cove 38 3.947 0.001
Marino Rocks 38 4.607 0.001
Northern Control 38 3.628 0.001
Northern Impact 38 4.281 0.001
Main Impact 38 2.160 0.011
Southern Impact 38 2.265 0.001
Southern Control 38 2.368 0.005
PERMDISP showed there were significant differences in dispersion (i.e. variability) among replicates
for the seven sites (n = 280; F6,273 = 6.689; P (perm) = 0.001) but not between sampling occasions (n =
280; F1,278 = 0.002; P (perm) = 0.996). There were no consistent trends for changes in variability
between sampling occasions, with both control and impact sites showing increases and decreases in
variability (Table 8). Overall, these multivariate analyses indicate that are no significant differences
in community structure among sites based on proximity to the area of presumed impact by sand
deposition at O’Sullivans Beach in 2009. Instead, small-scale spatial (i.e. site) and temporal (i.e.
seasonal) effects seem to be driving differences in community structure among sites.
21 | P a g e
Table 8: PERMDISP pair-wise comparisons of the dispersion during each sampling occasion for each
site. Bolded text indicates significant differences in dispersion (i.e. variability) between sampling
occasions (May and October).
Type Site May October F1,38 P(perm)
Control Hallett Cove 34.041 < 45.249 20.616 0.0004
Control Marino Rocks 26.638 < 39.917 14.182 0.0016
Control Northern Control 47.155 > 40.086 3.63 0.0994
Impact Northern Impact 47.112 > 31.667 23.83 0.0002
Impact Main Impact 41.129 < 46.970 4.268 0.0562
Impact Southern Impact 44.511 < 48.447 1.5797 0.2319
Control Southern Control 45.831 > 36.331 10.674 0.0027
Hallett Cove
Marino Rocks
Northern Control
Northern Impact
Main Impact
Southern Impact
Southern Control
Stress = 0.19
Figure 10: Multidimensional scaling (MDS) plot showing sites (see key) and sampling occasions (May:
solid-fill; October: no fill). MDS plots highlight the relative similarity of replicate samples to each
other, using relative distances between points to represent high-dimensional relationships, in this
case, for community structure (i.e. multiple species and their abundances). Essentially, two points
that plot close to each other represent macrofaunal communities with a similar structure, two points
plotting far apart represent dissimilar communities.
22 | P a g e
Dicathais orbita abundance and size
Timed search surveys of the subtidal environment were undertaken both north and south of the
O’Sullivans beach boat harbour (main impact zone and southern control respectively). Preliminary
observations of the control site south of the boat harbour appear to reveal no major differences in
size and abundance of D. orbita between survey dates March 2008 – April 2009. Consistent with the
intertidal observations of sediment deposition, preliminary observations of the subtidal environment
in the area north of the O’Sullivans beach boat harbour indicate a higher proportion of sediment
accumulation. Field observations revealed that the occurrence of sediment engulfed D. orbita on
rock surfaces with potential implications for survivorship of buried individuals via means of
starvation or asphyxiation if sedimentation remains for extended periods. The November 2009
sampling indicated a lower total abundance (Figure 11a), but a similar mean shell length of whelks at
both the control and impacted sites (Figure 11b).
(a)
(b)
Figure 11 D. orbita (a) abundance, and (b) mean shell length from shallow subtidal surveys
undertaken on a rocky reef at the control (South of O’Sullivans Beach boat ramp) and the impacted
(North of O’Sullivans Beach boat ramp) sites from March 2008 to November 2009
23 | P a g e
Discussion
Monitoring of the intertidal zone at the O’Sullivans Beach, Port Stanvac and northern control sites
revealed no evidence for persistent impacts from sand dumping on the intertidal reefs. Overall the
variation in percent cover of sand and sessile organisms, as well as the abundance and diversity of
invertebrates appears to be within the range of natural temporal and spatial variability within this
region. The highest percent sand cover was actually recorded at the Northern Impact site in
November 2007 prior to the sand dredging event. Although substantial sand cover was anecdotally
observed in the main impact area immediately after the sand dumping at O’Sullivans Beach (Figure
1), it appears that the storm event prior to the May 2009 was successful in rapidly clearing the
majority of accumulated sand. Nevertheless, some fairly large and partially anoxic sand patches
were recorded in the main impact area during May 2009. These occurred behind rock ledges > 1m
tall and at distances between 12-23 m from low tide. However, by October 2009, all of these sand
patches had completely cleared from the intertidal reef.
The most noticeable effect of the sand dumping at O’ Sullivan Beach appears to be a substantial
increase in the percent cover of bare substrate at the main and north impacts sites between
November 2007 and May 2009 (> 25%). Correspondingly there is a drop in the percent cover of
algae. However, some reduction in the algal cover and increases in bare substrate were also
observed at the control sites and most likely represents a seasonal effect, as photosynthetic alga are
less prolific in the winter months. By October 2009, the algal and sessile invertebrate cover had
increased at all sites, most likely due to increased light availability and rising water temperatures in
spring. The organismal cover remained relatively low at the main and south impact sites when
compared to the pre-impact 2007 surveys, which could indicate slower recovery due to residual
effects from the sand accumulation. However, these sites still showed greater cover that the
northern metropolitan controls sites and generally appeared to be recovering well. As reported
previously from studies on the Isle of Mann, season appears to be the over-riding factor influencing
rocky shore communities (Prathep et al., 2002). The productivity of algae can vary seasonally, in
addition to the supply and movement of sediment, thus providing a naturally heterogeneous
environment.
The high sand cover at the North impact site may have influenced the relatively low diversity of
invertebrates found at this site in the May 2009 surveys, relative to the pre-impact surveys by
Dutton and Benkendorff (2008). Nevertheless, as the sand cleared in October, 2009, the diversity
recovered at this site, indicating no long-term detrimental effects. The main impact site was actually
found to have the highest diversity immediately after the sand dumping in May 2009 and whilst this
decreased in the October 2009 surveys, the diversity still remained within the range of all non-
impacted control sites. However, the relatively high number of barnacles at the impact sites in the
May 2009 surveys is of potential interest. Pineda (1994) have reported higher settlement of the
barnacle Chthamalus spp. at sites where rocks are surrounded by unsuitable sandy substrate,
possibly because settlement is intensified when suitable habitat is scare. Thus it is is possible that
24 | P a g e
barnacle recruitment during the sand dumping at O’Sullivans Beach resulted in unusually high
settlement in the remaining exposed rocks.
The abundance of invertebrates generally showed a lot of variability between sites and survey
periods. The molluscs showed particularly low abundance at all sites in May, relative to the October
2009 surveys, which is likely due to the lower algal cover in May, as these are mostly herbivorous
gastropods. The May surveys were also conducted on higher tides than the October 2009 surveys
(Table 1), which might also influence the observed differences in abundance. Conversely, surveys of
the whelk Dicathais orbita in the shallow subtidal region indicated a drop in abundance from April to
November 2009. The lower abundances of this predatory gastropod at both the impact and control
sites may be indirectly attributable to algal cover. Algal proliferation is normal for spring time in
metropolitan waters and this cover can inhibit the timed search surveys for whelks, as more time is
required to search through algal fronds that were not in such profusion during the April surveys.
Additional observations indicate that there is greater algal diversity and cover at the impact site,
which receives less human traffic than the control site. This may have resulted in fewer whelks
recorded at the control site in the October surveys. Overall, this data provides no evidence for
significant impacts on the intertidal or subtidal mollusc populations at O’Sullivans Beach as a result
of the sand dumping. These results are consistent with previous experimental sand manipulations on
rocky shores, which indicated recovery on intertidal communities one month after sand addition had
ceased (Huff and Jarett, 2007).
Sand fluctuation and sand scour is a natural event that occurs on many intertidal reefs (Tyler et al.,
1982; Littler et al., 1983). As a consequence intertidal communities might have adapted to rapidly
recover from temporary sand inundation. Many intertidal organisms will opportunistically colonise
and recruit into any suitable habitat that has been opened up by sand-stress (Littler et al., 1983).
Consequently, these systems may be naturally resilient to one-off sand deposition events, such as
occurred at O’Sullivans Beach. Intertidal systems along the Fleurieu Peninsula, South Australia may
recover particularly well over the winter period, during which high tides and substantial wave action
can clear away the accumulated sand prior to spring recruitment and colonisation events.
Nevertheless, the scale of impact is likely to depend on the amount of sand dumped, the duration of
sand retention, any repeated occurrence and the timing of these events. Experimental studies on
Mediterranean rocky shores have shown that the impacts of sedimentation and recolonisation of
the bare rock are dependent on the time at which succession is initiated (Airoldi and Cinelli, 1997).
Furthermore, studies in New Zealand have illustrated the importance of time and space in relation to
sand impacts regulating the interaction between invasive and indigenous species of rocky shore
mussels (Zardi et al., 2008). Consequently, caution should be taken before extrapolating these
results to other situations, including different times of the year and locations.
In conclusion, this study provides useful baseline data that could be used in future monitoring
programs to assess intertidal impacts associated with on-going activities in the O’Sullivans Beach and
Port Stanvac area. Additional dredging activities have been undertaken more recently in this area for
the O’Sullivans Beach waste water treatment plant. Furthermore, the construction of a
breakwater/jetty on O’Sullivans beach may lead to long term changes in the siltation and erosion
pattern along this coast. Future monitoring efforts should preferably commence with replicated
surveys undertaken in advance of the impact. Replicated surveys should occur pre-, during and post
25 | P a g e
dredging at control and impact sites to account for natural seasonal variation. The local community
should also be informed in advance of any proposed dredging events, with descriptions of their likely
duration and potential impacts. This report may help alleviate community concerns with respect to
the recovery of intertidal communities at O’Sullivans Beach subsequent to the sand dumping event
in April 2009. However, it should not be used to predict the impacts of sand dumping on intertidal
reefs at other locations and times.
References
Airoldi, L., & Cinelli, F., 1997. Effects of Sedimentation on subtidal macroalgal assemblages: an
experimental study from a Mediterranean rocky shore, Journal of Experimental Marine Biology and
Ecology, vol. 215: 269-288.
Airoldi, L., & Hawkins, SJ., 2007. Negative effects of sediment deposition on grazing activity and
survival of the limpet Patella vulgate, Marine Ecology Progress Series, vol. 332: 235-240.
Anderson, M.J., Gorely, R.N., Clarke, K.R., 2008. Permanova+ for PRIMER: Guide to Software and
Statistical Methods. Plymouth Marine Laboratory, United Kingdom.
Benkendorff, K. Fairweather, P. and Dittmann, S. (2008) Intertidal Ecosystems. Ch 10 In Natural
History of the Gulf St Vincent. Ed. S. Shepherd, S. Bryars, Kirkegaard, I., Harbison, P. and Jennings J.T.
Royal Society of S.A. Adelaide, Australia.
Clarke, K.R. Warwick, R.M. (2001) Change in Marine Communities – An Approach to Statistical
Analysis and Interpretation, 2nd
Edition. PRIMER-E, Plymouth.
Clarke , K.R. Gorley, R.N. (2006) PRIMER v6: User Manual/Tutorial. PRIMER-E, Plymouth.
Dutton, A. and Benkendorff, K. (2008) Biodiversity Assessment and Monitoring of the Port Stanvac
Intertidal Reef. Report to the Adelaide and Mt Lofty Natural Resource Management Board. (Flinders
University, Adelaide).
Huff, T.M., & Jarett, J.K., 2007. Sand addition alters the invertebrate community of intertidal
coralline turf, Marine Ecology Progress Series, vol. 345: 75-82.
Littler, M.M., Martz, D.R., Littler, D.S., 1983. Effects of recurrent sand deposition on rocky intertidal
organisms: importance of substrate heterogeneity in a fluctuating environment, Marine Ecology
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Noble, W.J., Cocks, R.R., Harris, J., Benkendorff, K., 2009. Application of anaesthetics for sex
identification and bioactive compound recovery from wild Dicathais orbita, Journal of Experimental
Marine Biology and Ecology, vol. 380:1-2: 53-60.
Pineda, J., 1994. Spatial and temporal patterns in barnacle settlement rate along a southern
California rocky shore, Marine Ecology Progress Series, vol. 107: 125-138.
26 | P a g e
Prathep, A., Marrs, R.H., Norton, T.A., 2003. Spatial and temporal variations in sediment
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390.
Pulfrich, A., Parkins, C.A., Branch, G.M., Bustamante, R.H., Velasquez, C.R., 2003. The effects of
sediment deposits from Namibian diamond mines on intertidal and subtidal reefs and rock lobster
populations, Aquatic Conservation: Marine and Freshwater Ecosystems, vol. 13: 257-278.
Schiel, D.R., Wood, S.A., Dunmore, R.A ., Taylor, D.I., 2006. Sediment on rocky intertidal reefs: Effects
on early post-settlement stages of habitat-forming seaweeds, Journal of Experimental Marine
Biology and Ecology, vol. 2006: 158-172.
Taylor, P.R., Littler, M.M., 1982. The roles of compensatory mortality, physical disturbance, and
substrate retention in the development and organisation of a sand-influenced, rocky-intertidal
community, Ecology, vol. 1982: 135-146.
Thompson, R.C. Crowe, T.P. and Hawkins, S.J. (2002). ‘Rocky intertidal communities: past
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Trott, T.J., 2004. Late 20th
-Century Qualitative Intertidal Faunal Changes in Cobscook Bay, Maine,
Northeastern Naturalist, vol. 11 (2): 325-354.
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temporal variation in natural populations. Aust. J. Mar. Freshw. Res. 42: 569-587.
Yanez, B., Carballo, J.L., Olabarria, C. Barron, J.J., 2008. Recovery of macrobenthic assemblages
following experimental sand burial, Oceanologia, vol. 50 (3): 391-420.
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27 | P a g e
Appendix
Table 1: Species list of summed total of individuals for each sampling site for (a) May and (b) October
2009.
(a)
(b)
Phylum Species
Marino Rocks Hallett Cove North Control North Impact
Sites
Main Impact South Impact South Control
Annelida Galeolaria caespitosa
Notoacmea flammea
Notoacmea petterdi
−
5
0
X
17
1
X
16
5
X
7
0
−
15
0
Mollusca Notoacmea spp.
Patelloida alticostata
Patelloida latistrigata
Patelloida spp.
Cellana tramoserica
Cellana solida
Nerita atramentosa
Montfortula rugosa
Chlorodiloma adelaidae
Diloma concamerata
Austrocochlea constricta
Austrocochlea porcata
Herpetopoma aspersa
Phasianella ventricosa
Austrolittorina unifasciata
Bembicium nanum
Bembicium vittatum
Neogastropoda spp.1
Siphonaria diemenensis
Siphonaria zelandica
Unidentified gastropod
Limnoperna pulex
Chtalamus antennatus
0
0
5
0
2
2
62
4
0
8
0
1
0
0
385
5
59
0
2
0
1
−
1349
0
0
1
0
0
5
80
0
0
6
0
1
1
0
339
8
11
3
3
3
3
−
3097
2
2
0
4
0
0
109
0
1
8
0
1
0
0
14
6
7
0
96
13
4
X
159
0
0
3
0
0
0
44
0
0
2
1
8
0
0
81
7
0
0
23
2
0
−
356
0
0
11
0
79
0
3
0
0
1
3
0
0
1
0
1
0
0
234
1
6
X
52
Crustacea Chamaesipho tasmanica
Eliminus modestus
62
6
0
5
0
1
309
0
0
0
Phylum Species
Marino Hallett Cove North Control North Impact
Site
Main Impact South Impact South Control
Annelida Galeolaria caespitosa
Pomatoceros taeniata
X
−
X
−
X
−
X
X
−
X
X
−
X
X
Mollusca Notoacmea flammea
Notoacmea spp.
Patella chapmani
Patelloida alticostata
Patelloida latistrigata
Patelloida spp.
Cellana tramoserica
Cellana solida
Cellana radiata
Nerita atramentosa
Diloma concamerata
Austrocochlea rudis
Austrocochlea constricta
Austrocochlea porcata
Austrolittorina unifasciata
Bembicium auratum
Bembicium nanum
Bembicium vittatum
Onchidella nigricans
Siphonaria diemenensis
Siphonaria zelandica
Unidentified gastropod
Limnoperna pulex
3
0
0
0
0
0
0
6
0
0
0
0
0
0
0
0
0
0
0
391
3
14
X
33
0
8
0
4
0
0
109
0
6
0
0
0
2
10
1
4
0
0
390
0
0
X
154
0
3
0
133
0
0
12
0
4
1
1
0
0
104
0
0
0
0
1640
1
2
X
52
0
0
0
268
0
21
272
1
11
6
0
0
0
97
0
3
4
0
1692
0
0
X
2
3
0
0
88
0
26
16
0
15
1
0
4
0
0
0
0
11
1
766
0
39
X
1
1
0
11
63
0
23
91
0
4
0
0
0
1
258
0
2
6
0
501
0
0
X
8
4
0
0
67
9
82
46
0
0
0
0
0
0
2
0
0
0
1
419
0
34
X
Crustacea Chtalamus antennatus
Chamaesipho tasmanica
Catomerus polymerus
54
0
0
41
0
0
667
0
0
780
0
1
61
19
0
497
67
0
82
0
0
28 | P a g e
