Vol. 7, Issue 11, Part A (2025)

The present study was carried out to assess the biomass and diversity of plankton in Litopenaeus vannamei culture pond (station 1) and effluent treatment pond, receiving the shrimp pond effluent (station 2) in comparison to a reference (station 3) of apparently an unpolluted coastal waters relatively free from any pollution, nor influenced by the effluents from the shrimp ponds. The density of phytoplankton was counted using Sedgewick rafter counting chamber and found to be dominant in station 1 (73400 to 164600 cells/l) during November 2013 and April 2014 compared to station 2 (39200 to 84000 cells/l) and station 3 (38400 to 75200 cells/l) whereas the species diversity index (H’) of phytoplankton was comparatively lower in station 1 (0.99 to 2.03) followed by station 2 (1.62 to 2.94) and station 3 (2.37 to 2.96). The maximum and minimum density was recorded during summer and monsoon season, respectively. With regard to zooplankton composition, station 1 recorded high density (182500 to 397500 numbers/m3) compared to station 2 (12500 to 352500 numbers/m3) and station 3 (97500 to 272500 numbers/m3). The species diversity index (H’) for zooplankton in station 1, 2 and 3 varied from 1.01 to 33, 2.39 to 2.95 and 2.37 to 2.96, respectively. The present investigation showed that the shrimp culture pond (station 1) had high densities of plankton with less species diversity than unpolluted coastal waters of station 3. This indicates that the presence of Vannamei farm near coastal area of Kalaignanapuram seemed to have no influence on plankton dynamics of coastal waters. The effluent treatment ponds receiving shrimp pond effluent (station 2) had only slight variation in the plankton diversity compared to the unpolluted station.