Tracking Decadal Changes in Palk Bay Coral Community Structure: A Multivariate Approach

摘要

The study assessed a decade long changes of the coral community structure in the Palk Bay region using multivariate analysis based on observed coral life-forms and its diversity between the years, 2002 and 2018. A total of 11 study sites were selected from Rameswaram Island to Mandapam coast. Live coral cover was found to be 27% (21% non-Acropora and 6% Acropora corals) during the study period 2002-2005. Principal component analysis (PCA) showed that there was a significant variability (PC1: 39.5% variance) in coral cover between the study site, Bison House and the rest of the study sites. In the study of 2014-2018, live coral cover observed was 17% and this included 11% non-Acropora and 6% Acropora corals. PCA showed that the contribution of live coral cover gradually reduced towards the northern part of Rameswaram Island. Metric multi-dimensional Scaling (MDS) showed that there were four clusters formed between the sites with 80% similarity as observed based on the life-form categories. There were three major clusters with 70% similarity observed based on coral diversity. The highest diversity index (Shannon-wiener) was observed at Olaikudah and Villunditheertham as 1.906 and 1.864 respectively. As of 2014-2018, the live coral status showed 37% less than that found during 2002-2005 study period. Variation of reef flat composition was studied using Depth-Invariant Index for the study period 2002-2005. This study has helped to understand the longitudinal gradient of incidence, temporal variations, and distribution pattern of coral reef community categories in the Palk Bay region.