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.

中文翻译：

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跟踪帕克湾珊瑚群落结构的十年变化：多元方法

这项研究基于2002年至2018年间观察到的珊瑚生命形态及其多样性，通过多变量分析评估了帕克湾地区珊瑚群落结构长达十年的变化。从拉梅斯瓦拉姆岛（Rameswaram Island）至曼达帕姆海岸。在2002-2005年的研究期间，发现活珊瑚覆盖率为27％（非鹿角珊瑚为21％，非鹿角珊瑚为6％）。主成分分析（PCA）显示，研究地点，Bison House与其余研究地点之间的珊瑚覆盖率存在显着差异（PC1：39.5％差异）。在2014-2018年的研究中，观察到的活珊瑚覆盖率为17％，其中包括11％的非珊瑚虫和6％的珊瑚虫。PCA显示，在拉梅斯瓦拉姆岛的北部，活珊瑚覆盖的贡献逐渐减少。度量多维标度（MDS）显示，根据生命形式类别，在站点之间形成了四个簇，它们具有80％的相似性。根据珊瑚的多样性，发现了三个主要的类群，它们具有70％的相似性。Olaikudah和Villunditheertham的最高多样性指数（Shannon-wiener）分别为1.906和1.864。截至2014–2018年，活珊瑚的状况比2002–2005研究期间的状况低37％。在2002-2005年的研究期间，使用深度不变指数研究了礁滩成分的变化。这项研究有助于了解波克湾地区珊瑚礁群落类别的发生率，时间变化和分布模式的纵向梯度。