OBSERVATIONS ON DENSITY, PERCENTAGE COMPOSITION AND SEASONAL VARIATIONS OF ZOOPLANKTON IN A PERENNIAL POND OF TRIPURA, INDIA IN RELATION TO PHYSICO-CHEMICAL FACTORS

The observation showed the existence of 17 species of zooplankton comprising of 12 species of rotifer, 3 species of cladocera and 2 species of copepod in a perennial pond of Tripura. During the two years study periods, highest density of rotifer (321 ind/l) recorded in the winter season and lowest density (79 ind/l) in summer while highest density of cladocera (153 ind/l) recorded in the summer and lowest density (43ind/l) in monsoon season and similar trend of seasonal succession in terms of density were also showed in the copepod fauna (117 ind/l in summer; 31 ind/l in monsoon) as that of cladoceran fauna. The percentage composition of different families under which different zooplankton species exist was recorded as well as percentage composition of each zooplankton species was also recorded. Physico-chemical factors of the studied perennial pond were also recorded. The simple correlation coefficient showed water temperature (r = - 0.9531, P<0.01) has negative and significant correlation with the zooplankton density. However, the stepwise multiple regression analysis showed that water temperature (P<0.01), dissolved oxygen (P<0.05), bicarbonate alkalinity (P<0.01), dissolved organic matter (P<0.01), phosphate phosphorus (P<0.05) have significant impact on the density of zooplankton in the studied pond. The study infers that although the different groups of zooplankton co-exist in the same water body, their density varies with different seasons of the year and presumably aquatic macrophyte substrata and suitable range of the abiotic factors (physico-chemical) conjointly act for the densities of zooplankton of the studied perennial pond.