SEASONAL DIFFERENCES IN ORGANOCHLORINE PESTICIDE CONCENTRATIONS OF ZOOPLANKTON AND FISH IN THE ARABIAN SEA

Zooplankton and fish samples taken from different locations in the nor thern Arabian Sea before and during the southwest monsoon were examine d for residues of DDT, its metabolites and aldrin. In the monsoon, the concentrations of total DDT (DDT + DDE + DDD) and aldrin in zooplankt on were, respectively, 4 and 5 times higher than the pre-monsoon conce ntrations while the corresponding increases in fish were 10 to 30 time s and 3 to 40 times, respectively. The presence of considerable amount s of primary DDT in samples obtained during the monsoon, coinciding wi th peak agricultural activity on land, indicated that (a) the pesticid e residue levels in these organisms were determined by the pattern of use on land and (b) the pesticide compounds entering this environment were rapidly disseminated. Also, pesticide accumulation by fish was ap parently dictated by their feeding habits. As observed from the lipid- normalised values, pelagic varieties accumulate more residues than the demersal ones during the pre-monsoon season white the opposite is tru e for the monsoon season. DDD was the major DDT metabolite present in all the samples. (C) 1997 Elsevier Science Limited.