Zooplankton diversity and physico-chemical conditions in three perennial ponds of Virudhunagar district, Tamilnadu.

Plankton diversity and physico-chemical parameters are an important criterion for evaluating the suitability of water for irrigation and drinking purposes. In this study we tried to assess the zooplankton species richness, diversity and evenness and to predict the state of three perennial ponds according to physico-chemical parameters. A total of 47 taxa were recorded: 24 rotifers, 9 copepods, 8 cladocerans, 4 ostracods and 2 protozoans. More number of zooplankton species were recorded in Chinnapperkovil pond (47 species) followed by Nallanchettipatti (39 species) and Kadabamkulam pond (24 species). Among the rotifers, Branchionus sp. is abundant. Diaphanosoma sp. predominant among the cladocerans. Among copepods, numerical superiority was found in the case of Mesocyclopes sp. Cypris sp. repeated abundance among ostracoda. Present study revealed that zooplankton species richness (R1 and R2) was comparatively higher (R1: 4.39; R2: 2.13) in Chinnapperkovil pond. The species diversity was higher in the Chinnapperkovil pond (H': 2.53; N1: 15.05; N2: 15.75) as compared to other ponds. The water samples were analyzed for temperature, pH, electrical conductivity alkalinity salinity, phosphate, hardness, dissolved oxygen and biological oxygen demand. Higher value of physico-chemical parameters and zooplankton diversity were recorded in Chinnapperkovil pond as compared to other ponds. The zooplankton population shows positive significant correlation with physico-chemical parameters like, temperature, alkalinity phosphate, hardness and biological oxygen demand, whereas negatively correlated with rainfall and salinity. The study revealed that the presence of certain species like, Monostyla sp., Keratella sp., Lapadella sp., Leydigia sp., Moinodaphnia sp., Diaptomus sp., Diaphanosoma sp., Mesocyclopes sp., Cypris sp. and Brachionus sp. is considered to be biological indicator for eutrophication.