Predation/disturbance effects of greater flamingos (Phoenicopterus ruber) on the benthic communities of two Southern African lagoons
Master Thesis
1992
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University of Cape Town
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Abstract
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.
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Bibliography: leaves 69-74.
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Glassom, D. 1992. Predation/disturbance effects of greater flamingos (Phoenicopterus ruber) on the benthic communities of two Southern African lagoons. University of Cape Town.