Benthos of Cochin backwaters receiving industrial effluents

Abstract

Faunal composition of benthos and its spatial and temporal distribution at 9 stations in the northern limb of the Cochin backwaters are studied. An industrial belt is located about 18 km upstream of barmouth, and the effluents are discharged into the river. This stretch with a station 2 km further upstream forms the area of study. Faunal groups/species are rich at barmouth (st 1), gradually decline upstream and record lowest density at the effluent discharge point (st 8). Five major and 26 other groups or organisms are encountered during the study. Polychaetes and molluscs are the only major groups present at all stations, Amphipods rand third being present at sts 1-7; followed by isopods and tanaidaceans. Polychaetes are most common and constitute the largest assemblage of benthic forms in the study area. The polychaete species <i>Capitella capitata</i> which is present in enormous numbers at or near the discharge site can be considered to be an indicator species of industrial pollution. Substrate characteristics and hydrographic features of the area are also discussed.