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harbour. No benthos sampling results have been reported for the Ben Schoeman Dock Basin or the outer areas of the harbour that would allow a determination of the extent of the apparent pollution effect on benthos distributions. AVS values do tend to decline in these areas and may be zero indicating that the sediments are oxic. If, as is likely, anoxia is the controlling variable it is probable that there will be benthos in the sediments with low to zero AVS levels. Distortion levels in community composition due to pollution effects or other stressors such as frequent surficial sediment suspension are, however, unknown. Outside the harbour, large numbers of juvenile rock lobsters can be found on the vertical faces of the outer harbour wall (Hazell et al. 2002). Other major components of the wall community are encrusting corallines, the barnacle Notomegabalanus algicola, the sea urchin Parechinus angulosus, the ribbed mussel Aulacomya ater, and sponges (Mayfield 1998). The relatively low coverage and biomass of mussels and the high cover of encrusting corallines at the wall contrast with nearby natural subtidal rocky shores, for example at Mouille Point, where mussels cover approx. 80% of the rocks and encrusting coralline cover is low (Mayfield 1998, Table 1). Harbours are a typical location for the introduction of alien species through ships calling at the port which may transport organisms on their hulls or in their ballast waters. Examples in the Port of Cape Town are the European shore crab Carcinus maenas, the anemone Metridium senile, which grows on loose, silt-laden boulders or other objects, and on the soft sediments on the floor of the Victoria and Alfred Basins, the red algae Schimmelmannia elegans, and the ascidian Ciona intestinalis (Robinson et al. 2005). Table 1: Average percentage cover and wet biomass (± standard error) of benthic organisms at the outer harbour wall and at Mouille Point. Percentage cover includes secondary cover (e.g. barnacle cover) and can thus exceed 100% (after Mayfield 1998). Benthos Harbour Wall %cover / g wet mass/m 2 ± SE Mouille Point %cover / g wet mass/m 2 ± SE Coralline algae 75 / 2235 ± 289 20 / 506 ± 192 Foliar algae
2000 at Robben Island revealed further growth to a breeding population of 5705 pairs (Crawford et al. 2000), which, assuming a ratio of 3.2 adults per breeding pair (Crawford & Boonstra 1994), amounts to an estimated population of 18 000 adult penguins. This was approximately equivalent to 12% of the global population at this time (data from Crawford 2006). Robben Island is therefore a critically important breeding site for the African penguin population. Figure 5 provides another view of fluctuations in penguin numbers utilising Robben Island via counts of birds coming ashore to moult. The main feature of this figure is the approximately monotonic increase in bird numbers to 2004 and then a sharp decline to the present (2006). This may be linked to food availability (primarily sardine Sardinops sagax), as the centre of abundance of this species appears to have moved east of Cape Point in the recent past (van der Lingen et al. 2005.). Moulters 20000 18000 16000 14000 12000 10000 8000 6000 4000 2000 0 1988/89 1990/91 1992/93 1994/95 1996/97 1998/99 2000/01 2002/03 2004/05 Year Figure 5: Recent trends in the numbers of penguins (adult and immature) that come ashore to moult on Robben Island (from Crawford 2006) Overall the African penguin population has decreased throughout the 20th century, at a rate that has led to its classification as Vulnerable under IUCN criteria (Crawford 1998, Barnes 2000). More recently apparent declines in nesting populations on specifically St Croix Island in Algoa Bay (Crawford 2006) indicates that this classification should be changed to Endangered. Satellite tracking data indicate that penguins forage mainly north and offshore of Robben Island generally within 20km of the island shores (DEAT/MCM unpublished data). It is therefore apparent that the larger Table Bay area comprises critical habitat for this species. Next to the large penguin colony, Robben Island supports the 3rd largest colony of Bank cormorants (120 breeding pairs in June 2000), which are also endemic to southern Africa. The 2nd largest colony is at Clifton Rocks, just south of Table Bay (Crawford et al. 2000, Figure 3). The global population of Bank cormorants have decreased drastically in the last three decades, from 8 672 breeding pairs to 4 888 pairs in 1995/97, and they are also considered Vulnerable (Barnes 2000). 20
Page 1 and 2: BEN SCHOEMAN DOCK BERTH DEEPENING S
Page 3 and 4: the test organisms. The EC 5 is usu
Page 5 and 6: Turbidity Upwelling Vulnerable Wrac
Page 7 and 8: Another important issue is the poss
Page 9 and 10: 6.2.1.3 Settlement of material susp
Page 11 and 12: 2 METHODOLOGY For the assessment tw
Page 13 and 14: The proposed deepening of the Ben S
Page 15 and 16: 4.3 Cumulative effects Table Bay re
Page 17 and 18: undetectable in 80% of the measurem
Page 19 and 20: 5.1.3 Biological communities The ma
Page 21 and 22: Supralittoral fringe (Littorina zon
Page 23 and 24: Niambia sp. Coleoptera Diptera Tylo
Page 25 and 26: Midlittoral zone - The intertidal o
Page 27: Fish - Nearshore and in the sandy b
Page 31 and 32: Table 2: Common whales and dolphins
Page 33 and 34: Table 3: Site, time, mean count (co
Page 35 and 36: 150000 125000 100000 Kg 75000 50000
Page 37 and 38: sensitive because of its conservati
Page 39 and 40: Schoeman Dock occurred in 1971 (Pro
Page 41 and 42: Table 7: Hydrocarbon distributions
Page 43 and 44: care concentration ranges for cadmi
Page 45 and 46: SS mg/l Boxplot for TSS 80 60 40 20
Page 47 and 48: The mean values calculated above ar
Page 49 and 50: o o possibility of the dredge spoil
Page 51 and 52: The gravel sized component of the s
Page 53 and 54: Table 12a: London Convention Annex
Page 55 and 56: Benthos distributions in Block #1 -
Page 57 and 58: 40 40 30 Site 1A 30 Site 1B % Speci
Page 59 and 60: 2 Cluster Dendrogram and MDS ordina
Page 61 and 62: the well developed ripples in the c
Page 63 and 64: 6 IMPACT IDENTIFICATION AND ASSESSM
Page 65 and 66: Accordingly the potential environme
Page 67 and 68: Impact Assessment Table No Mitigati
Page 69 and 70: are summarised in the table and it
Page 71 and 72: Figure 21b: Predicted number of day
Page 73 and 74: considered to be low. Further, the
Page 75 and 76: A A B B B Figure 23a and b: Predict
Page 77 and 78: dependent on these include the harm
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structures. The apparent lack of su
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Diving birds such as cape cormorant
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Figure 24: The predicted worst case
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Figure 25 depicts the simulation mo
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6.2.3.2 Alteration of benthic biolo
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Impact Assessment Table No Mitigati
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Nature of impact - Turbid plumes of
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Figure 26b: Predicted worst case ex
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Figure 27b: Predicted worst case ex
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suspended sediment concentrations i
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Figure 28a: Dredge spoil dump site
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6.2.3.6 Elevated water column turbi
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The evaluation with mitigation is:
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Figure 29a: Predicted exceedance in
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6.3 Cumulative Impacts The proposed
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Impact summary Table (cont.) Impact
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Impact summary Table (cont.) Impact
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mitigated by ensuring that the Cutt
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operations at Coega Port. Prepared
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Glassom D., K. Prochazka and G.M. B
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Protekon 2006. Port of Cape Town co
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BEN SCHOEMAN DOCK BERTH DEEPENING Specialist ... - Transnet

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