ABSTRACT: Phytoplankton biodiversity and water quality of national wetland, Sukhna Lake, Chandigarh (Lat. 30° 44''14 N, Long. 76° 47'' 14 E), India were examined in the present study. During the present study (April 2009 to September 2009), phytoplankton composition and physico-chemical characteristics of water are indicative of mesotrophic condition in three different collection zones (Z_A, Z_B and Z_C) of the lake. The species richness displayed fair variety of algal species (89 taxa). The community was dominated by the members of chlorophyceae and cyanophyceae. Highest phytoplankton density (2082 individual/ L) and species diversity (0.928-2.628) was found during the summer season in the wild area (Z_A) where there was no anthropogenic activity. The area with maximum disturbance in water column (Z_C) showed minimum phytoplankton density (164/L) and species diversity (0.991-2.319). Phytoplankton densities have significantly positive correlation with TDS(r= 0.669, significant at 0.05 level), chloride(r= 0.717, significant at 0.05 level) and significantly negative correlation with BOD(r= 0.623, significant at 0.05) in Z_A and significantly positive correlation with bicarbonate alkalinity(r= 0.728, significant at 0.01 level) and calcium hardness(r= 0.672, significant at 0.05 level) in Z_B.

Key words: Lake Sukhna; Ecology; Physicochemical parameters; Phytoplankton; species diversity.