Taxonomy and ecology of South African reef corals

Doctoral Thesis


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University of Cape Town

This thesis provides a complete taxonomic review of South African hermatypic Scleractinian reef corals, a description of coral communities on northern Natal coral reefs, experiments isolating the influence of the most important abiotic factors forcing these communities and finally management suggestions for the marine reserves within which these reefs are situated, based on the results of the ecological investigation. The taxonomic part reviews the entire hermatypic scleractinian coral fauna of South Africa and Southern Mozambique, including also material from the Atoll Bassas da India in the Mozambique channel. The study of coral communities on Northern Natal coral reefs revealed major differences in the nature of the reefs and the community structure of the reef corals from typical coral reefs in the Inda-Pacific. The study lead to the assumption that wave-action and sedimentation are the most important abiotic factors influencing these coral communities. These hypotheses were experimentally tested in the field and in the laboratory, using indicator species for specific community types, as identified in the community study. Testing fragment survival of the hard coral Acropora austera confirmed the assumption that wave action is an important factor shaping coral communities by only allowing this species to dominate in depths greater than 18m. Four hard- and five soft coral species were used to quantify the effects of sedimentation on the coral communities. It was demonstrated that long-term sedimentation had greater influence on soft corals than on hard corals, leading to tissue necroses and local bleaching. These experiments confirmed the assumption that sedimentation is a major forcing factor on South African coral communities. The final part of thesis provides management options for the St. Lucia and Maputaland Marine Reserves focussing on conservation of the coral communities. The findings obtained in the ecological investigation allowed to identify which activities in the reserves have to be controlled in order to minimize damage to the coral communities by park visitors.

Bibliography: p. 492-494.