28-Seasonal changes In Zooplankton community thriving in wastewater - Fed Fish Ponds

Abstract

East Calcutta Wetlands, Ramsar site No 1208, receive domestic and industrial wastes of Kolkata city both in solid and liquid forms. In the wetlands several small and large ponds are excavated which receive the raw wastewater and apply them in pisciculture. Zooplankton plays a major role in pisciculture, as they are the primary food for juvenile fishes. Present study records the aspects of zooplankton diversity for 12 months in relation to physico-chemical environment of four selected fishponds comprising of 3 nursery tanks (Site 1, 2 and 3) and a large stocking pond (Site 4). The study revealed the occurrence of 45 species of zooplankton, among thes3 12 species of Cladocera, 4 species of Copepoda, 27 species of Rotifera, and 2 species of Ostracoda were recorded. Mesocyclops leuckartiwas the most frequently encountered zooplankton. Paracyclops sp. was very rare, encountered only in five occasions at Site 2 and Site 3. Among the cladocerans Moina brachiata and M. micrura were most abundant. Diaphanosoma sarsi, Ceriodaphnia cornuta and Daphnia sp. were also found in adequate numbers. The genus Moinodaphnia sp. was very rare, found only twice at Site 2 and Site 3. Brachionus calyciflorus, B. quadridentatus & B. urceolaris were more frequent among the rotifers and were found in all the sites. Abundance of different groups of zooplankton was correlated with the physico-chemical parameters of the pond water. Total zooplankton showed significant negative correlation with Total Dissolved Solids (r = — 0.98; p < 0.05) and significant positive correlation with DO(r = 0.98; p < 0.05). Total copepods and total cladocerans separately exhibited significant positive correlations with Gross Primary Productivity (r = 0.99 and 0.97 respectively; p < 0.05). Site wise variation in dominance, diversity, evenness and richness were also calculated.