This study reports the spatial distributions of diatom assemblages and potential relationships between diatom diversity and environmental variables (C/N ratio, CaCO 3 %, clay mineralogy) using multivariate analyses in surface sediments of the Akkulam-Veli Lake. Surface sediment samples were collected at 19 sites throughout the lake to analyse diatom distribution, TOC, N, CaCO 3 %, clay mineralogy and sediment texture. The results suggest that the clay fraction is predominant in the eastern flank, whereas sand fraction is more in the western flank. TOC% and CaCO 3 % in the lake floor sediments are attributed to high organic activity within the lake and contributions from the vegetation around the lake margins. The results suggest that N is being added to the lake from secondary sources from catchment area leading to eutrophication of the lake. Further, clay mineralogy of the sediment samples reveals that kaolinite mineralogy dominates in clay fractions. Diatom studies show rich diversity of freshwater, marine and brackish diatoms and abundance of pollution-reflecting species such as Cyclotella sp. and Navicula sp.