The present study was carried out for three consecutive years (2011-2014). Investigations were carried out on the diversity and percentage composition of phytoplankton species in the tail race of Dikhow river. Dikhow is a southern tributary of the mighty river Brahmaputra originating from Naga Hills. Phytoplankton diversity was used as an indicator to assess the water quality of the river. The aim of this study was to understand the pollution status of the river and analyze the diversity and distribution pattern of phuytoplankton which was influenced by the rainfall. During the study, four groups of phytoplankton were recorded which belong to group Chlorophyceae, Euglanophyceae, Bacillariophyceae and Myxophyceae. Bacillariophyceae and Chlorophyceae were more abundant both qualitatively and quantitatively. The percentage distribution of Bacillariophyceae and chlorophyceae was found to be 50% and 32.37 % respectively. Abundance of Bacillariophyceae with 50% relative occurrence could

Phytoplankton, Brahmaputra, Bacillariophyceae, Chlorophyceae, Euglanophyceae

It is summarized from the present study that the down stream of Dikhow river is polluted. In the present study phytoplankton diversity was dominated by diatoms. Diatoms respond to a certain number of environmental and biological variables. Because of their sensitivity, they may act as reliable bioindicators. They act as pollution indicator in the present study. On the other hand the diversity indices also indicate the pollution level of the river. Bacillariophyceae and Chlorophyceae dominance indicate organic pollution in the river. The effect of anthropogenic stress was also identified through the phytoplankton structure and diversity study. Exposure of organic pollution was identified during the study, Hence certain anthropogenic activities near the river should be regulated to ensure its protection and conservation. Which may contribute to national development and improvement of water resources

Dutta, B. (2019). Phytoplankton as an Indicator of the River Water Quality: A case Study in the Tail race of River Dikhow, Assam, India. Biological Forum – An International Journal, 11(2): 50-55.