Limnological Characteristics of Jannapura Tank in Bhadravathi Taluk of Karnataka, India

A detailed study was carried out in Jannapura tank near Bhadravathi town of Shimoga district on physico-chemical parameters, fish diversity, aquatic macrophytes and Plankton composition during January to December 2008. The results of physico-chemical parameters were compared with Bureau of India Standards (BIS) and World Health Organization (WHO) standards. The study revealed that, tank water is under eutrophic category as it possesses high BOD, phosphate and nitrate. Among fish diversity a total of 24 species belonging to 19 genera in 10 families of five orders were recorded. Majority of t h e s p e c i e s (2 1) w e r e n a t i v e. T h r e e s p e c i e s , viz.,Ctenopharyngodon idellus (Valenciennes), Cyprinus carpio(Linnaeus) and Oreochromis mossambica (Peters) were exotic species. Among aquatic plants, a total of 13 species belonging to 11 families were recorded. Pistia stratiotes and Alternanthera philoxeroides were regarded as pollution tolerant aquatic macrophytes and be used as a biological indicator for eutrophication. A total of 75 species of phytoplankton were recorded, of which Bacillariophyceae (22 species) and chlorophyceae (27 species) were dominant. 26 zooplankton species were also recorded. In the present study as per water quality recommended by WHO and BIS standards, the tank water is not suitable for drinking and cooking purposes. The present findings revealed that the surface quality of the tank is productive and eutrophic.