Chlorophyll a and pheo - pigment as indices of biological productivity in the inshore surface waters off Cochin

Abstract

Estimations of surface chlorophyll a and pheo-pigment concentrations were made at two stations (10 and 20m) in the inshore waters off Cochin which are correlated with related environmental parameters. In 1987 the maximum chlorophyll a production in both the stations was during pre-monsoon (2.3 and 2.1 mg/m3) while in 1988 it was during post monsoon period (3.4 and 3.2 mg/m5). In general a considerable reduction in overall production was noticed in 1987 over 1988, particularly during both monsoon and post-monsoon periods. The total annual chlorophyll a production was found to be 38.4 mg/m3 in 1987 whereas in 1988 it was 62.2 mg/m5 adding stations I & II together. The total annual pheo-pigment production was estimated to be 37.2 mg/m3 for stations I and II put together in 1988, contributing about 62% of chlorophyll a. As regards the environmental parameters, nutrients, especially phosphate showed positive correlation and nitrite negative relation to chlorophyll production. Variations in the observed values during 1987and 1988 are attributed to the intensity of monsoon rain fall and the freshwater discharge from the river and lake system.