The study of phytoplankton diversity and its seasonal variation was carried out by sampling water taken from the Santragachi Lake, of West Bengal between November 2009 and July 2010. Various physico-chemical variables were recorded and the correlation of this with phytoplankton density was established using Canonical Correspondence Analysis. This showed that the density of phytoplankton was higher when temperature and nutrients were increased. A total of 29 phytoplankton taxa belonging to Chlorophyta (10), Cyanobacteria (8), Charophyta (5), Bacillariophyta (4), and Euglenozoa (2) were recorded from nine samples taken within the study period. Chlorophyta species dominated mostly in variety and percentage composition while Euglenozoa species representatives had the least expression. Bio-indication showed a low diverse community in the monsoon period with better water quality than in pre- and post-monsoon seasons. Various diversity indices (Shannon–Wiener diversity index, Gleason species richness index, Pielou evenness index, and Naughton dominance index) were used to establish the seasonal variation of phytoplankton. The Shannon–Wiener diversity index was most useful in indicating the trophic status of the water as well as the pollution status, which in this case, depicted a moderate level of pollution of this lake

A total of 44 taxa were observed in monthly sampled phytoplankton of the Shibpukur pool in Burdwan, West Bengal between March, 2010 and February, 2011. The most abundant taxa belong to Charophyta, followed by cyanobacteria, diatoms and euglenoids. Bio-indication shows that the pool community preferred low alkaline, low mineralized and low organically polluted water. The total phytoplankton density showed its maximum values in May, 2010. The Shannon-Weaver diversity index and the Pielou evenness value were found to be highest during the post-monsoon season. The Simpson dominance index and the Margalef index of richness were highest in the pre-monsoon season. The total phytoplankton density showed a highly significant positive correlation with pH and salinity and significant positive correlation with air temperature, water temperature, dissolved oxygen and total suspended solids. Among the reported 44 phytoplankton taxa only 3 showed a random distributional pattern. The Bray-Curtis Cluster analysis and the comparative statistics reveal two groups of phytoplankton assemblages in respect to the monsoon seasons. The successive communities form a continuum corresponding to Colwell’s Constancy (C) category. The calculated indices, CCA, and bio-indication analysis exhibit a low pollution level in the Shibpukur pool that can be used as a model of aquatic community dynamics under seasonal fluctuation in the monsoon climate, applicable for monitoring of water bodies in the West Bengal Province

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