SOFT-SEDIMENT DWELLING MACROINVERTEBRATES OF RAJAPUR BAY, CENTRAL WEST-COAST OF INDIA

Thirtyfour species of soft sediment dwelling macro-invertebrates were recorded in Rajapur bay at the proposed effluent discharge location of nuclear power plant. The fauna mainly composed of polychaetes (42.52% ), molluscs (39.03%), crustaceans (7.86%), sipunculids (1.23%), echiur ids (7.86%) and cephalochordates (1.5%). Deposit feeder spionidae-Prio nospio pinnata and filter feeder bivalve-Pecten sp. formed the dominan t and co-dominant species respectively. Maximum population density and wet biomass recorded were 2,675 m - 2 (XBAR = 445 +/- 507) and 26.5 g m-2 (XBAR = 6.01 +/- 6.2 1) respectively. Annual benthic production w as estimated to be 12.02 g.m-2.y-1. Species diversity varied from 0.91 to 3.61 (XBAR = 2.2 +/- 0.75). High species diversity value showed th e stability of the environment. Dominance diversity curve showed evene ss of benthic fauna. This was reflected on the competition equilibrium period of the population. Species similarity cluster of different sta tions were formed largely due to habitat specific and feeding behaviou r of the species. The spatio-temporal variations and community structu re fluctuations of macro-invertebrates are mainly due to the effect of southwest monsoon and the impact of localized biotic and abiotic fact ors. Benthic fauna in this bay is in natural ecological balance and fr ee from an apparent effect of environmental imbalances. The base line data generated here can be used to assess the impact of pollution, if any, in future.