Phytoplankton diversity in pichavaram mangrove waters from south-east coast of India.

The results of an investigation carried out during September 2002 to August 2003 on hydrography, composition and community structure of phytoplankton including chlorophyll 'a' (Chl-a) content and primary productivity (PP) of the Pichavaram mangrove (South-east coast of India) are reported. Atmospheric and surface water temperatures varied from 30.0 to 34.8 degrees C and from 29.7 to 34.2 degrees C respectively while the light extinction coefficient values (LEC) (K) ranged between 3.2 and 14.9. Salinity values varied from 9.6 to 35.4 per thousand and the pH ranged between 7.2 and 8.6. Variation in dissolved oxygen content was from 3.2 to 6.5 ml l(-1). The ranges of inorganic nutrients viz., nitrate, nitrite, phosphate and silicate were: 7-36.23, 0.31-5.46, 0.28-3.70 and 12.26-56 64 microM respectively Chlorophyll 'a' content ranged between 0.20 and 105.60 microg l(-1) and the ranges of gross and net primary productivities (PP) were: 16.54-826.8 and11.52-610.2 mg Cm(-3) hr(-1) respectively. Presently a total of 94 species of phytoplankton were identified. Among these, the diatoms formed predominant group. Population density of phytoplankton varied from 400 to 3,21,000 cells(-1). While the peak diversity (5.23 bits/ind.) of the phytoplankton was observed during summer season, the maximum population density was found during summer season coinciding with the stable hydrographical conditions.