Predation/disturbance effects of greater flamingos (Phoenicopterus ruber) on the benthic communities of two Southern African lagoons

Bibliography: leaves 69-74.Greater Flamingos, Phoenicopterus ruber, were excluded from intertidal areas of two lagoons and subtidal areas of one of these on the Namibian coastline. Macrofaunal and meiofaunal numbers increased at all exclusion sites, but taxon-specific responses were variable. Both intertidal sites were polychaete dominated; subtidally amphipods formed dense tube mats that covered the substrate. All except one macrofaunal species showed significant response to caging. Relative to controls, macrofaunal numbers increased approximately three times inside subtidal exclosures, and one and a half times intertidally, but diversity indices were similar between treatments. There was some evidence that amensalistic interactions developed between macrofauna within exclosures. Intertidally at Walvis Bay rneiofauna showed little response to flamingo exclusion, but subtidally all groups showed statistically significant responses to treatments. At Sandwich Harbour, foraminifera and ostracod abundance changed significantly. Bacterial counts were lower in exclusions at all sites, but significantly so only at Sandwich Harbour, which was the only site where chlorophyll concentrations did not change significantly. Sediment particle size composition was unaffected at all sites. Eh and organic content of sediments changed least subtidally; pH was affected by the treatment at both Walvis Bay sites, but not at Sandwich Harbour. Partial cages, used as cage controls, indicated that results were not artefacts caused by caging. Overall, it was clear that P. ruber was important in structuring communities in the areas studied. In the absence of P. ruber, physical disturbance may be the most important force structuring benthic communities

Plastic ingestion by estuarine mullet Mugil cephalus (Mugilidae) in an urban harbour, KwaZulu-Natal, South Africa

Coastal urban environments have high plastic pollution levels, and hence interactions between plastic debris and marine life are frequent. We report on plastic ingestion by mullet Mugil cephalus in Durban Harbour, KwaZulu-Natal, South Africa. Of 70 mullet (13.0–19.5 cm total length), 73% had plastic particles in their guts, with a mean of 3.8 particles per fish (SD 4.7). Plastic ingestion showed no relation to digestive tract content or fish length. White and clear plastic fibres were ingested most commonly. This urban population of M. cephalus had a higher incidence of plastic ingestion than has been reported in studies on fish from other coastal areas or the oceanic environment.DHE

Time Integrated Metal Accumulation on Pellets in an Industrial Harbour “Durban Harbour”

Once in the environment, preproduction plastic polymers between 2–5 mm in size, also known as pellets, can cause physical harm to animals that mistake them for food as they have been reported to accumulate toxic substances, including on their surface. However, the rate of metal enrichment on pellets is not well investigated. In October 2018, Durban experienced a storm that resulted in ±2000 tons of polyethylene pellets being spilt into Durban Harbour, which caused environmental pollution concerns. This event provided a unique opportunity to study metal accumulation on pellets. Pellets were collected at one-month intervals for 6 months following the spill from October 2017 to March 2018, and metal concentrations were compared to concentrations found on pellets collected before the spill. The pellets were digested using a mixture of concentrated nitric acid (55%) and sulphuric acid (60%) at a ratio of 3:1 and analysed for numerous trace metals (Al, As, Pb, Cd, Cr, Fe, Cu, Mn, Ni, and Zn) using the Inductively Coupled Plasma Optical Emission Spectroscopy (ICP-OES). Pellets collected in Durban Harbour prior to the spill in a related study (unpublished data) showed higher metal accumulation; however, there was no evident linear increase in metal concentration in pellets over time. ANOVA showed no significant difference for all metals (p > 0.05) in metal concentration between months; however, there was a significant difference between aged and newly introduced pellets

Short-term effects of an oil spill on the West coast of the Cape Peninsula, South Africa

Abstract. In 1994, the sinking of the 'Apollo Sea' off the West coast of South Africa led to the deposition of ca. 2 500 tons of heavy fuel oil over 150 km of coastline. The impact of the spill on rocky shore invertebrates, rock-pool fish fauna and rock lobsters was assessed by conducting surveys shortly after the spill, and again two months later. Where possible, results of these surveys were compared with existing data from before the sinking of the Apollo Sea. Among the fish fauna of rockpools, changes in total density of fishes were largely due to changes in the abundance of Clinus superciliosus and were within the range of natural variation for the species and the community as a whole. Community structure of the rock-pool fish fauna also remained unaffected. At three of four impacted rocky shore sites no changes could be detected in overall benthic community structure, although the winkle Nodilittorina africana was affected. At the fourth site, a boulder beach, statistical analysis showed distinct differences in community structure between heavily and lightly contaminated areas, as well as between all areas compared with previously existing data. There were also significant changes in the lightly oiled areas between the first and second surveys after the spill. Oil-fouled lobster were found at one of three sites investigated. Ca. 7 % of the seabed in this particular area was polluted. Antennae and forelegs of almost all lobsters in the vicinity of the oil were fouled. Examination of the gut-contents confirmed that oil inhibits the ability of lobster to feed. Although there was no evidence that mortalities of lobster were caused by the spill, growth rates may be reduced by the decreased feeding rate. Overall, the impact of the spill was strikingly less than might have been predicted from the effects of other oil spills

Spatio-temporal patterns of coral recruitment at Vamizi Island, Quirimbas Archipelago, Mozambique

Spatial and temporal patterns of recruitment of reef corals were assessed for the first time in Mozambique by deploying settlement plates at various spatio-temporal scales between October 2012 and October 2013. The abundance of juvenile corals (5−50 mm in diameter) was assessed along transects. Settlement of acroporids was highly seasonal, with 97% of spat settling between July and October 2013. Pocilloporids settled throughout the year, peaking slightly between October 2012 and January 2013. The annual mean larval settlement of up to 1 135 spat m–2 was comparable to that on other East African reefs, but was dominated by acroporids, which constituted over 80% of all spat, whereas pocilloporids settle in higher densities in Kenya and South Africa. The peak settlement season also differed from other African locations. A greater proportion of variance in settlement rates occurred at the spatial scale of kilometres (between sites) and centimetres (between settlement plates) than at the scale of metres (between subsites), implying that most patchiness occurs at those scales. The peak in acroporid settlement coincided with the period of multispecific spawning, with settlement occurring as early as nine days after a spawning event. As no similar spawning events have been reported for other reefs in the area, our results suggest that these spawning events strongly influence overall annual settlement rates and promote high levels of self-seeding at Vamizi. There was no relationship between settlement of larvae to settlement plates and juvenile density on adjacent reefs, suggesting either variable levels of early post-settlement mortality or high interannual variability in settlement.Keywords: coral reproduction, juveniles, larval settlement, recruitment, Scleractinia, Western Indian Ocea