Bioaccumulation and distribution of organochlorine residues across the food web in Lagos Lagoon, Nigeria
Eighteen organochlorine pesticide (OCP) residues were measured in the water, sediment, plankton, benthic invertebrates and fish in various sections of the Lagos Lagoon in 2014 to investigate their bioaccumulation and distribution in the food web. The analysis was done using gas chromatography with an electron capture detector. The concentrations of OCPs in water and sediment ranged from 0.00 to 2.24 μg kg−1 and 0.00 to 1 673.57 μg kg−1 , respectively. The sediment had the highest deposition of OCPs, with a total concentration of 2 953.84 μg kg−1 . Lindane and heptachlor epoxide had the highest mean concentrations in the sediment, 1 673.57 μg kg−1 and 1 122.74 μg kg−1 , respectively, while other OCPs were also found in the biota. Bentho-pelagic fishes had the highest biota-sediment accumulation factor (BSAF) in nine OCP residues, ranging from 1 to 32, and benthic invertebrates had the highest BSAF in three OCP residues, ranging from 1 to 91. The trend in total concentration of OCPs in the lagoon was sediment > Melicertus kerathurus > Eleotris soaresi > Pomadasys jubelini > Tilapia guineensis > Callinectes amnicola > plankton > water. The transfer of organochlorine residues in the food chain and its distribution in the trophic levels was influenced by habitat, environmental conditions, feeding habit and biochemical composition of individual populations. The total residual concentration of OCPs in shellfish and fish ranged between 0.16 ppm and 0.69 ppm. This concentration is quite high compared to the Federal Ministry of Environment limit of <0.01 ppm, and can be harmful if the trend is not checked. Continuous monitoring procedures need to be put in place for environmental safety.
Keywords: biota, gas chromatography, pesticide, plankton, sediment