Spatial variation in the health of coral reef communities of Palk Bay, southeast coast of India

This study was conducted to assess the health of the coastal ecosystem based on bio-physical assessment of the coral reef ecosystem at Palk Bay. A total of 11 sites along the coast from the eastern part of Rameswaram Island to Mandapam were chosen for this study. Good live coral cover (acroporid and non-acroporid corals) of 30.08 +/- 6.72% was recorded in the eastern part of Rameswaram Island. Principal component analysis demonstrated that the contribution of live coral cover was closer to the selected study sites of the eastern part of Rameswaram Island. Metric multi-dimensional scaling analysis showed three major clusters with 75% similarity based on life-form categories observed in the reef ecosystem. In this study, there was a significant segregation of study sites of the eastern part of Rameswaram Island in two clusters with 80% similarity because of their richness of live coral cover. Multi-dimensional scaling based on coral species diversity showed three major clusters with 50% similarity. Principal component analysis showed that the major contribution and abundance of coral species were closer to the northern part of Rameswaram Island. Moreover, Shannon-Wiener species diversity index of this region was in the range of 1.592-1.856, which was higher than the other sites. Hence, it was observed that there is no relationship between mean live coral cover and coral species diversity index of the reef ecosystem. The impact of biological indicators such as Halimeda algae and Palythoa sp. (Zoanthids) on the reef ecosystem was also analyzed. About 31 species of live corals belonging to 9 families and 18 genera were recorded during the study period. The outcome of this study helped in the understanding of the health of the ecosystem based on the intensity of mean live coral cover and coral species diversity. It also made it easier to understand the longitudinal variations and distribution pattern of coral reef community categories.