Factors influencing spatial patterns on coral reefs around Moorea, French Polynesia

Spatial patterns of 5 components of the macrobenthos [corals, macroalgae, mollusks, sponges, and echinoderms) at 42 stations on 4 reef types were compared in Moorea Fifteen a b ~o t ~c and biotic factors were measured and included in Canonical Correspondence Analyses. Macrobenthic communities were dominated by corals and macroalgae. Two major gradients (along the bays, and from the fringing reef to the outer reef slope) were found for corals, macroalgae, and echinoderms. The gradients were realized at a small spatial scale in Moorea [less than 2 km from the fringing reef to the outer reef slope at 35 m depth), while the same type of variation occurs at a large spat~al scale (more than 100 km) on the Great Barrier Reef. Abiotic and biotic factors explained a large amount of the variance in sponge and coral communities, but less for mollusks and markedly less for macroalgae and echinoderms. Some of the factors identified in this study, such as depth, sand coverage, and algal coverage, have been also reported as controlling factors in other coral reefs. In contrast, the high abundance of sea urchins and its impact seem to be characteristic of coral reefs around Moorea.