Studies on phytoplankton diversity in response to abiotic factors in Veeranam lake in the Cuddalore district of Tamil Nadu.

The phytoplankton samples were collected from the Veeranam lake for a period of one year from March-2005 to February-2006. The physico-chemical parameters of water such as air-temperature, water temperature, pH, salinity, dissolved oxygen, electrical conductivity and total dissolved solids were observed and their ranges were: 30.1-36.5 degrees C, 29.0-34.4 degrees C, 7.9-8.4, 1.2-2.5 mgl(-1), 7.6-9.2 microS and 2.5-5.2 mgl(-1). Totally 160 species of phytoplankton belonging to different taxonomic groups were identified. Among these 74 species to belong to Bacillariophyceae, 43 species to Chlorophyceae, 38 species to Cyanophyceae and 5 species to Euglenophyceae. The phytoplankton density was high (1705 cells l(-1)) during the summer season and low (760 cells l(-1)) during the winter season. Bacillariophyceae formed the dominant group. Species diversity index (H'), species richness (SR) and species evenness (J') were calculated.