Coral and rock reef habitats in southern Sri Lanka; Patterns in the distribution of coral communities

This study describes the coastal reefs of southern and southwestern Sri Lan ka including reefs at Hikkaduwa, Unawatuna, Rumassala, Weligama, Mirissa an d Polhena. Two reef types are defined: coral reefs and rock reefs. The cora l reefs were all fringing the coast. Some of them were described as lagoon reefs with an adjacent reef slope, while others were typified as nearshore reefs without typical zonation patterns. However, there were similarities a mong coral reefs as most of them had a significant coral growth; the overal l average live coral cover was almost 50%. The dominant coral genera were A cropora followed by Montipora and Pocillopora. The reef slopes had a low co ral cover as they were dominated by coralline rock and patches of sand. The rock reefs were dominated by large boulders and rocky outcrops and the cor al growth was sparse, but small colonies of different coral genera were pre sent. Generally, the rock reefs were situated in more exposed areas and at greater depths, further offshore, than the coral reefs. The development of the reefs in this study was influenced by a range of factors. Important nat ural processes seemed to be related to hydrodynamics and sedimentation. How ever, as all these reefs are situated near the shore, they are also influen ced by various human activities including fishing, boating, reef walking, s norkelling, pollution, and sedimentation, which clearly have altered reef s tructure at some sites.