STUDIES ON THE DIVERSITY OF PHYTOPLANKTONS AND THEIR SEASONAL VARIATION IN KUNIGAL TANK, TUMKUR DISTRICT, KARNATAKA

Aquatic water resources play vital role in maintaining environmental sustainability. Surface water bodies like lakes and tanks are degraded by increased industrial activities and urban runoff which deteriorate the water quality and their environment. Phytoplanktons are the autotrophic components of the plankton community and form the important part of the aquatic food chain. Aquatic environmental productivity is directly associated with phytoplankton density. Physico-chemical factors are directly related to their production. The temperature is found to be the main driving force for phytoplankton dominance. The members of phytoplankton community are important for their role in food production and energy transfer in trophic dynamics and water ecosystems. In the pollution study, they are represented as biological indicators of water quality. The purpose of this study was to investigate the phytoplankton diversity for a period of two years from February 2014 to January 2016 in Kunigal tank and to assess the species composition and seasonal variations of this faunal group. The water samples were collected from five sampling sites between 7 am to 9 am on monthly basis. From each sampling site, 50 liters of water sample were collected, filtered through 60μm mesh size plankton net. The concentrated water sample was fixed and preserved in 4% formalin. one ml of concentrated sample was transferred into Sedge-wick Rafter cell and counted under Olympus binocular microscope. The results revealed the occurrence of 62 species of phytoplanktons belonging to five groups - Chlorophyceae, Bacillariophyceae, Cyanophyceae, Desmidaceae and Euglenophyceae. Chlorophyceae is represented by 16 species belonging to 15 genera, Bacillariophyceae is represented by 12 species belonging to 9 genera, Cyanophyceae is represented by 18 species belonging to 17 genera, Desmidaceae is represented by 12 species belonging to 8 genera and Euglenophyceae is represented by 4 species belonging to 2 genera. Among these, Chlorophyceae shows its dominance. The percentage composition of phytoplankton species was found as Chlorophyceae>Bacillariophyceae > Cyanophyceae>Desmidaceae > Euglenophyceae. Shannon-Weiner Index value of phytoplanktons ranged between 2.0 - 3.0 and Simpson Index values are found between 0 and 1, which indicated the good diversity and light pollution level. The results of this study explained the diversity and pollution status of Kunigal tank and helps in implementing strategies for water quality management and productivity of the tank.