Abstract

• The seasonal fluctuations in phytoplankton assemblages and the controlling environmental factors were investigated for 24 months along the coast of Tanintharyi from June 2013 to June 2015. A wide fluctuation in cell abundance 72,450-714,396 cells l-1 at Kawthaung, 47,416-947,501 cells l-1 at Myeik, 8,930-28,439 cells l-1 at Kampani, 8,976-17,888 cells l-1 at Ye and 5,162-16,986 cells l-1 at Setse were noted during the study period. Amongst, Kawthaung and Myeik stations had the highest phytoplankton abundance whereas Ye and Setse stations showed remarkably lower abundance. A clear seasonal trend was found at all five stations with a sharp peak in the pre-monsoon months and a gradual decrease in the monsoon and post-monsoon periods. Phosphate concentration was relatively high at Myeik and Kawthaung stations, and also the increase of water temperature and salinity in the pre-monsoon months may probably stimulate a high abundance of phytoplankton. On the other hand, a decrease of phytoplankton abundance was found in the monsoon season which was characterized by low water temperature, low salinity, and low level of nutrients.