Coral Cover, Zonation and Diversity on Reef Slopes of Chagos Atolls, and Population Structures of the Major Species

Substrate cover by corals, soft corals, sand, bare rock and algae was determined by several means for seaward reef slopes of the Central Indian Ocean atolls of Peros Banhos and Salomon, Chagos Archipelago, and in the lagoon of the former. Cover of hard substrate by coelenterates averages 80 O/O between 3 and 42 m, and calcareous algae dominate above and below these depths. Alcyonarian corals contribute about 15 "/,I of thls between 3 and 23 m; at least 5 '/U of rock at all sites is uncolonised.