The results of an investigation carried out during September 1999 to August 2000 on hydrography, composition and community structure of phytoplankton including chlorophyll 'a' (Chl-a) content and primary productivity (PP) of the Coleroon Estuary (Southeast coast of India) are reported. The concentration (pm) of nitrate and phosphate ranged from 7.9-69.9 and 0.9-9.0 respectively. The ranges of values of Chl-a (mg m³) and PP (mg C m³ hr¹) were 1.7-3.2 and 0.2-2.1. While the peak diversity (4.32 bitslind.) of the phytoplankton was observed during premonsoon season, the maximum population density (37,127 cellsll) was found during summer. The spatio-temporal variations observed in the hydrobiological features appeared to be related to the pattern of meteorological events. The Coleroon Estuary is more fertile and supports a rich and diverse phytoplankton.

Coleroon Estuary, diversity of phytoplankton