A biogeographic assessment of phytoplankton richness and composition in the Andaman Archipelago and the potential links to anthropogenic and environmental impacts: A multivariate approach

Abstract

We report here a year-round baseline assessment on phytoplankton diversity and abundance from the pristine coastal waters of the Andaman Islands (September 2011–October 2012). A total of 84 phytoplankton species belonging to 47 genera were recorded from the North to South Andaman Islands. The maximum number of phytoplankton diversity (84 species under 47 genera) was recorded during the northeast monsoon (NEM) at a highly urbanized coastal environment like South Andaman Islands, whereas the minimum diversity (53 species under 34 genera) was recorded during the inter-monsoon (IM) period at the less anthropogenic activity sites viz. North and Middle Andaman Islands. All over seasons, the community composition of phytoplankton was mostly dominated by diatoms (45%–87%) followed by dinoflagellates (11%–46%) and blue–green algae (1%–35%). Besides, the abundance of phytoplankton was recorded as a gradual decrease from South Andaman to North Andaman Islands. The Canonical Correspondence Analysis (CCA) revealed the impact of physicochemical variables on phytoplankton assemblages. Thus, the temperature, salinity, and nitrite were the major environmental variables that influenced phytoplankton assemblage and distribution in the coastal waters of the Andaman Islands. The Principal Component Analysis (PCA) showed a strong variability of phytoplankton diversity in the South Andaman Islands (PC1: 32.6–36.2% variance). In addition, the Metric-multidimensional Scaling analysis also showed the gradual species intensity in the South Andaman than the Middle and North Andaman Islands.