Polychlorinated biphenyls contamination in Lagos lagoon and impacts on the benthic macroinvertebrates community structure

Abstract

Polychlorinated biphenyls (PCBs) are a group of persistent organic pollutants (POPs) that have generated global concerns for constituting hazards in the aquatic ecosystems. Their lipophilic nature makes them to accumulate in the sediment of water bodies resulting to some negative impacts on the benthic macroinvertebrates. This study was conducted to investigate the impact of the PCBs contamination on the benthic macroinvertebrate assemblage in the study area. Benthic samples were collected at six study stations for six months using Van-veen grab sampler. Sediments samples were removed from the benthic samples into a glass container and taken to the laboratory where extraction and clean up were conducted in preparation for Gas Chromatograph-Mass Spectrometer (GC-MS) analysis. This was performed using an Agilent 5977B GC/MSD system coupled with Agilent 8860 auto-sampler, a Gas (GC-MS) equipped with an Elite-5MS (5% diphenyl/95% dimethyl polysiloxane) fused with a capillary column (30 × 0.25μm ID × 0.25 μm df). The remaining part of each benthic sample was sieved in situ through a 0.5 mm sieve and preserved in 10% formalin inside a plastic container for further analysis in the benthic laboratory following standard procedures. Results obtained from this study indicate that there is a negative linear relationship between PCB concentrations and species abundance, diversity, equitability, evenness, and richness. This suggests that PCBs contamination in sediments may pose considerable ecotoxicological risk to the community structure of benthic macroinvertebrates of the lagoon. There is also a need to improve the waste management systems to prevent the entry of PCBs and other persistent organic pollutants into the Lagos lagoon and ultimately conserve the health of this very important marine ecosystem.