LEVELS OF ORGANOCHLORINE PESTICIDE RESIDUES IN BIOTIC AND ABIOTIC COMPONENTS OF THE LAGOS LAGOON, NIGERIA

Abstract

High concentrations of organochlorine pesticides (OCs) in a marine environment such as the Lagos Lagoon demands great attention since this Lagoon serves as a major source of sea foods to the people of lagos and its environs. This work examined the levels of OCs in both biotic and abiotic components of Lagos Lagoon. Surface water, sediment, zooplankton, phytoplankton, benthic invertebrates and fishes from four locations on Lagos lagoon were analysed for OCs using gas chromatograph equipped with Ni Electron capture detector. The concentrations were as follows: sum BHC (Benzene Hexachloride) 1777.80g/kg, heptachlor epoxide (1134.39g/kg), sum DDT (Dichloro Diphenyl Trichloroethane) 207.13g/kg, methoxychlor 85.43g/kg, chlorothalonil 83.84g/kg, heptachlor 69.89g/kg, aldrin 223.87g/kg, endosulfan1 11.09g/kg, di-eldrin 46.50g/kg, endosulfan2 16.59g/kg, endrin 16.23g/kg endosulfan sulfate 3.95g/kg, ?-cyhalothrin   53.65g/kg. The high concentrations of DDT and BHC suggested their recent usage in the study area or recent transport through rivers and canals that discharge into the lagoon. Sediment was found to have the highest percentage OCs of 78.08%, water had the lowest of only 0.09%, phytoplankton/zooplankton had 5.09%, benthic invertebrate had 8.76% and fishes 7.97%. The percentage distribution indicated the level of transfer as the OCs biomagnified along the aquatic food webs from lower tropic level to higher tropic level.