State of the Bay Report 2010-Final - Anchor Environmental

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2009, 2010) all employed diver-operated suction sampling equipment to collect their samples. For example, the study conducted in 1975 in Saldanha Bay (Moldan 1978) made use of a modified von Veen grab sampler weighted to 20 kg which sampled an area of 0.2 m 2 from the surface fraction of sediment whilst all of the studies since 1999 have made use of a diver-operated suction sampler which sampled an area of 0.08 m 2 to a depth of 30 cm. The former sampling technique (von Veen grab) would be expected to sample a smaller proportion and a different range of benthic macrofauna due to its limited ability to penetrate the sediment beyond the surface layers. The suction sampler employed in subsequent studies effectively samples to a much deeper depth, where many of the larger organisms, like prawns and worm, are expected to occur. The exact location of sites sampled during 1975 and 1999-2009 studies also differed slightly (Figure 8.1), which further confounds comparisons between these different data sets. Sampling for the State of the Bay reporting has been standardised to be comparable with the techniques employed in the later studies (Christie and Moldan 1977, Bickerton 1999 and Anchor Environmental Consultants 2004, 2009, 2010) both in terms of the equipment employed (diver operated suction sampler) and sites that are sampled. This is to ensure that direct comparisons between sampling events is possible and any changes in the community composition reflect real changes in the environment and are not an artefact of the sampling techniques used. Details of these methods are provided below. 8.3 Approach and methods used in monitoring benthic macrofauna in 2010 8.3.1 Sample collection A total of 25 sites were sampled for benthic macrofauna in 2010, nine of which were in Small Bay, seven in Big Bay and nine in Langebaan Lagoon (Figure 8.2). Samples were collected using a diver-operated suction sampler, which sampled an area of 0.08 m 2 to a depth of 30 cm and retained benthic fauna >1 mm in size in a muslin bag. Three suction samples were taken at each site and pooled, resulting in a total sampling surface area of 0.24 m 2 per site. These methods correspond exactly with those employed in 1999, 2004, 2008 and 2009 and thus facilitate comparisons between these sets of data. The water depth ranged at the sampling stations ranged from 1.8 m to 21.0 m, with the shallowest sites being those in Langebaan Lagoon (Table 8.1). Samples were stored in plastic bottles and preserved with 5% formalin. In the laboratory, samples were rinsed of formalin, stained with Rose Bengal to aid in identification of biological material. All fauna were removed and preserved in 1% phenoxetol (Ethylene glycol monophenyl ether) solution. The macrofauna were then identified to species level where possible, but at least to family level in all instances. The biomass (blotted wet mass to four decimal places) and the abundance of species were recorded for each sample. 8.3.2 Statistical Analysis The data collected from this survey were used for two purposes 1) to assess spatial variability in the benthic macrofauna community structure and composition between sites (Small Bay, Big Bay and Langebaan Lagoon) in 2010 and 2) to assess changes in benthic community structure over time (i.e. in relation to the 1999, 2004, 2008 and 2009 surveys). Both the spatial and temporal assessments are necessary to provide a good indication of the state of the system. In addition, the ecological indicators were linked to environmental variables in an effort to ascertain what the dominant drivers of change are. State of the Bay 2010: Saldanha Bay and Langebaan Lagoon 154
Table 8.1. Depth at each of the sites sampled in 2010. Small Bay Depth (m) Big Bay Depth (m) Langebaan Lagoon Depth (m) SB1 9.9 BB20 21.0 LL31 4.6 SB2 8.0 BB21 10.2 LL32 4.0 SB3 6.3 BB22 12.5 LL33 3.1 SB8 11.1 BB25 11.6 LL34 4.9 SB9 15.5 BB26 16.0 LL37 1.8 SB10 7.4 BB29 16.6 LL38 6.3 SB14 16.0 BB30 3.9 LL39 4.7 SB15 13.0 SB16 17.0 8.3.2.1 Community structure and composition LL40 3.8 LL41 3.3 Changes in benthic species composition can be the first indicator of disturbance, as certain species are more sensitive (i.e. likely to decrease in abundance in response to stress) while others are more tolerant of adverse conditions (and may increase in abundance in response to stress, taking up space or resources vacated by the more sensitive species). The statistical package PRIMER 6 (Clarke and Warwick 1993) was used to analyze the benthic macrofauna data. Cluster analysis was performed in order to identify ‘natural groupings’ between samples (sites). Prior to cluster analysis data were root-root (fourth root) transformed and converted to a similarity matrix using the Bray-Curtis similarity coefficient. A dendrogram and a multi-dimensional scaling plot (MDS) were constructed from the similarity matrix in order to graphically view similarities between sample sites (Figure 8.4). Samples (sites) with similar species composition and abundance cluster together in such a plot, while those that are less similar are placed further apart in the cluster diagrams and ordination plots. Stress values associated with MDS plots are influenced by reduced dimensionality and increasing quantity of data (Clarke and Warwick 1994), both of these factors resulting in higher stress values. Stress values
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State of the Bay 2010: Saldanha Bay
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TABLE OF CONTENTS Anchor Environmen
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11 BIRDS 234 Anchor Environmental 1
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LIST OF FIGURES Anchor Environmenta
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Anchor Environmental Figure 4.27. O
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Anchor Environmental Figure 7.3. Ch
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Anchor Environmental Figure 9.10. C
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Anchor Environmental Figure 12.1. N
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Anchor Environmental samples were c
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EXECUTIVE SUMMARY Anchor Environmen
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Anchor Environmental matter in the
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Anchor Environmental considered mos
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Anchor Environmental again in 2004,
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Anchor Environmental Populations of
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GLOSSARY Alien species An introduce
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1 INTRODUCTION Anchor Environmental
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2 STRUCTURE OF THIS REPORT Anchor E
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Anchor Environmental complicates ma
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Anchor Environmental observed deter
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Anchor Environmental 4 ACTIVITIES A
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Fish factories Small craft harbour
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Anchor Environmental Aerial photogr
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Anchor Environmental interferes wit
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Anchor Environmental Figure 4.7. Nu
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o Decrease in oxygen concentrations
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Anchor Environmental Upgrades to th
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Anchor Environmental Figure 4.9. A)
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Anchor Environmental (possibly link
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Anchor Environmental Prestedge Reti
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Anchor Environmental the constructi
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Number and types of vessels enterin
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Anchor Environmental is contained b
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Anchor Environmental include the be
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o 33 3’S o 33 10’S Saldanha Bay
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Anchor Environmental (1956) UNDER T
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Free ACtive Chlorine (mg/l) Amonia
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Faecal coliforms (org/100 ml) Chemi
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4.3.7 Storm water Anchor Environmen
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Anchor Environmental sites (concent
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Anchor Environmental Discharges fro
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Anchor Environmental Table 4.9. Det
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5 WATER QUALITY Anchor Environmenta
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Anchor Environmental Stander (1977)
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Anchor Environmental coast, result
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Anchor Environmental likely as a re
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Anchor Environmental Construction o
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Anchor Environmental Table 5.2. Per
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Page 103 and 104: Counts per 100ml of sample Counts p
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Page 107 and 108: 5.6 Trace Metal Contaminants in the
Page 109 and 110: State of the Bay 2010: Saldanha Bay
Page 111 and 112: Lead(mg/kg) Mercury (mg/kg) Cadmium
Page 113 and 114: 6 SEDIMENTS 6.1 Sediment particle s
Page 115 and 116: 6.1.2 Sediment Particle size result
Page 119 and 120: 100% 90% 80% 70% 60% 50% 40% 30% 20
Page 125 and 126: % POC 18 16 14 12 10 8 6 4 2 0 % PO
Page 127 and 128: Percentage Percentage 1.8 1.6 1.4 1
Page 129 and 130: o 33 3’S o 33 10’S Yacht Club B
Page 131 and 132: Figure 6.12. Variation in the conce
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Page 135 and 136: concentrations are 56 and 29 times
Page 137 and 138: threshold of 1.2 mg/kg established
Page 139 and 140: Cadmium (mg/kg) 8 7 6 5 4 3 2 1 0 C
Page 141 and 142: Copper (mg/kg) 45 40 35 30 25 20 15
Page 143 and 144: 16000 14000 12000 10000 8000 6000 4
Page 145 and 146: In summary, elevated trace metal co
Page 147 and 148: 6.5 Summary of sediment health stat
Page 149 and 150: 7.1 Long term changes in seagrass i
Page 151 and 152: 7.2 Long term changes in Saltmarshe
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Page 159 and 160: (clustering of similar groups) (Meg
Page 161 and 162: The Big Bay samples BB 25 and BB29
Page 163 and 164: 2007/08 dredging. Other signs of th
Page 165 and 166: Wet mass per m² Wet mass per m² 4
Page 167 and 168: Big Bay Crustaceans and polychaetes
Page 169 and 170: Average number of individuals per m
Page 171 and 172: Number Individuals per m² Number I
Page 173 and 174: 8.4.2 Abundance Biomass Indices 8.4
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Page 177 and 178: Table 8.5. W statistics at all stat
Page 179 and 180: Figure 8.15: Variation in the diver
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Page 183 and 184: Cu (mg/kg) Cd (mg/kg) Ni (mg/kg) Pb
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Page 189 and 190: Brittle star ( Ophiuroidea spp) Sea
Page 191 and 192: 9.2 Approach and Methodology 9.2.1
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Page 195 and 196: 9.2.3 Data Analysis The similaritie
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Percentage Cover 80 70 60 50 40 30
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Evenness Shannon Wiener 0.9 0.8 0.7
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2005 2008 2009 2010 Dive School Jet
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Table 9.5. Results from the SIMPER
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In general, the inter-annual differ
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The temporal distribution of M. gal
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Consistent with the previous years,
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Saldanha and Langebaan. Results fro
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The average abundance of the four m
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Anchor Environmental Figure 10.5. A
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Anchor Environmental Figure 10.7. A
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Anchor Environmental Within Big Bay
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Anchor Environmental 2008 and 2009
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Anchor Environmental the islands, b
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Anchor Environmental at Saldanha ar
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their main prey species, sardines a
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Anchor Environmental attributed to
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Number of breeding pairs 800 700 60
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11.3 Birds of Langebaan Lagoon 11.3
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Anchor Environmental Figure 11.11.
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Anchor Environmental for the gannet
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Taxon Anchor Environmental Occurren
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Taxon Anchor Environmental Occurren
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Anchor Environmental 13 MANAGEMENT
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Anchor Environmental their operatio
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Anchor Environmental concentrations
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Anchor Environmental changes that p
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Anchor Environmental and slight imp
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Birdlife International. 2010. URL w
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Anchor Environmental penguins Sphen
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Anchor Environmental Game, E.T., Gr
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Anchor Environmental Kerwath, S. E.
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Anchor Environmental Moldan, A. 197
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Anchor Environmental Robinson, T.B.
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Anchor Environmental Tunley KL, Att
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