State of the Bay Report 2010-Final - Anchor Environmental

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8 BENTHIC MACROFAUNA 8.1 Background It is important to monitor biological criteria in addition to physio-chemical and ecotoxicological variables as biological indicators provide a direct measure on the state of the ecosystem. Benthic macrofauna are the biotic component most frequently monitored to detect changes in the health of the marine environment. This is largely because these species are short lived and therefore their community composition responds relatively rapidly to changes in environment quality over time (Warwick 1993). Given that they are also relatively non-mobile (as compared with fish and birds) they tend to be directly affected by pollution and they are easy to sample quantitatively (Warwick 1993). Furthermore they are well-studied scientifically, compared with other sediment-dwelling components (e.g. meiofauna and microfauna) and taxonomic keys are available for most groups. In addition, community response to a number of anthropogenic influences has been well documented. Benthic macrofauna community responses to anthropogenic impacts include changes in the growth rates of individual organisms, changes in reproductive output, and mortality, all of which can lead to changes in the relative abundance of individual species and hence community composition, reduction in the number of species present, and even complete disappearance of benthic organisms under severe circumstances (Warwick 1993). Common anthropogenic impacts of benthic macrofauna communities include physical disturbance (e.g. dredging), increased organic inputs (eutrophication) which can lead to hypoxia or even anoxia in sediment, elevated levels of trace metals, hydrocarbons and/or other anthopogenically produced compounds (e.g. pesticides) in sediments. The main aim of monitoring the health of an area is to detect the effects of stress, as well as to monitor recovery after an environmental perturbation. There are numerous indices that can be used to examine changes in community structure and hence ecosystem health, which are based on benthic invertebrate fauna information. These indices include those based on community composition, diversity and species abundance and/or biomass. Given the complexity inherent in environmental assessment it is recommended that several indices be used (Salas et al. 2006). The community composition, diversity, and species abundance and biomass of soft bottom benthic macrofauna samples, collected in Saldanha Bay and Langebaan Lagoon in 2010, are considered in this chapter. 8.2 Historic data on benthic macrofauna communities in Saldanha Bay The oldest records of benthic macrofauna species occurring in Saldanha Bay date back to the 1940’s, prior to the construction of the iron-ore jetty and Marcus Island causeway. Available data from this time is mostly anecdotal (i.e. non-quantitative), and is not comparable with subsequent studies, and as such cannot be used for establishing conditions in the environment prior to any of the major developments that occurred in the Bay. Moldan (1978) conducted a study in 1975 where the effects of dredging in Saldanha Bay on the benthic macrofauna were evaluated. Unfortunately, this study only provided benthic macrofauna data after the majority of Saldanha Bay (Small Bay and Big Bay) had been dredged. A similar study conducted in 1975 (Christie and Moldan 1977), examined the benthic macrofauna in Langebaan Lagoon, using a diver-operated suction sampler, and the results thereof provide a useful description of baseline conditions present in the Lagoon from this time. State of the Bay 2010: Saldanha Bay and Langebaan Lagoon 152
Figure 8.1. Benthic macrofauna sampling stations in 1975, 1999, 2004 and 2008. Several subsequent studies, conducted in the period 1975-1990, examined the benthic macrofauna communities of Saldanha Bay and/or Langebaan Lagoon, but are also, regrettably not comparable owing to the fact that techniques used to collect these samples were different from those used in earlier and subsequent studies. Samples from these earlier studies were mostly collected using some form of grab sampler, while the more recent studies (and some of the older studies - Christie and Moldan 1977, Bickerton 1999 and Anchor Environmental Consultants 2004, State of the Bay 2010: Saldanha Bay and Langebaan Lagoon 153
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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 101 and 102: Anchor Environmental Table 5.8. Per
Page 103 and 104: Counts per 100ml of sample Counts p
Page 105 and 106: Counts per 100ml of sample 10000 10
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
Page 133 and 134: The concentrations of metals in sed
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: 7.2 Long term changes in Saltmarshe
Page 155 and 156: Table 8.1. Depth at each of the sit
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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
Page 175 and 176: and percentage organic nitrogen (PO
Page 177 and 178: Table 8.5. W statistics at all stat
Page 179 and 180: Figure 8.15: Variation in the diver
Page 181 and 182: percentage of mud compared to Lange
Page 183 and 184: Cu (mg/kg) Cd (mg/kg) Ni (mg/kg) Pb
Page 185 and 186: contaminants. Furthermore dredging
Page 187 and 188: areas even 5 months after the clear
Page 189 and 190: Brittle star ( Ophiuroidea spp) Sea
Page 191 and 192: 9.2 Approach and Methodology 9.2.1
Page 193 and 194: cover data for both mobile and sess
Page 195 and 196: 9.2.3 Data Analysis The similaritie
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Page 199 and 200: stands of the kelp Ecklonia maxima
Page 201 and 202: Plocamium spp. Ecklonia maxima Scut
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20 40 A Group 1 B 60 Similarity C G
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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 2009). The eff
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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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