Biodiversity survey towards conservation of subtidal reef habitats in KwaZulu Natal : biogeography and depth patterns

Includes bibliographical references (pages 49-58).Subtidal reef communities in KwaZulu-Natal (KZN), South Africa are poorly known. This lack of knowledge is problematic as the biodiversity of these reefs may be severely impacted and inadequately conserved. This study documents and describes subtidal benthic communities occurring on reefs at four depth categories along the whole length of the coast. A distinct difference between northern reefs from those in the south and central parts of the province emerged with substantiating evidence of a discrete biogeographic separation at Cape St Lucia. Pairwise ANOSIM tests found no significant differences in community composition of reefs along a depth range of 10 m to 30 m at nine localities in KZN. However, differences among localities were significant at both regional (R = 0.607, P = 0.1%) and local (R = (1.792, P = 0.1%) scales. In the north, trends in species assemblages and functional groupings revealed a higher percentage cover of fauna (mainly corals) at shallower depths and a greater coverage of algae on deeper reefs. In the southern localities algae dominated shallower reefs while filter-feeding epifauna were more prevalent at deeper depths. Species richness, evenness and diversity were highest at 10m in the northern coral-dominated region while in the central/south region diversity peaked in the intermediate depth zone (15 - 25 m). Appropriate measures to conserve representative habitats in each biogeographic zone are necessary. Further research to assess biodiversity at a finer scale, as well as the establishment oflong-term monitoring to quantify natural variability and human effects, are required