Bioaccumulation of polycyclic aromatic hydrocarbons, histopathological alterations and parasito-fauna in bentho-pelagic host from Snake Island, Lagos, Nigeria

Abstract

This study investigates the bioaccumulation of polycyclic aromatic hydrocarbons, trophic microbial biomass, parasite prevalence, antioxidant enzyme responses and histological alterations in assessing anthropogenic impacts in Snake Island, Lagos, Nigeria. Two sample locations were chosen based on the type and nature of human activities: Ilase (fishing-based) and Ibasa (petroleum industry-based) communities. Fifteen PAH congeners were analysed from water, sediment, benthic invertebrates, three species of bentho-pelagic fishes and their parasito-fauna using GC/FID. Also, estimated from these samples were trophic microbial biomass, stress enzymes and histopathological alteration index of the fish gill. A significant proportion of PAHs was found in sediments originating from Ilase and Ibasa communities compared to all other samples analysed. Percentage distribution in the various compartments of the former was water, 2.67%; sediment, 91.28%; benthos, 1.19%; fish, 3.15%; and parasite, 1.71%. The corresponding PAH values obtained for Ibasa were 57.83%, 40.07%, 0.00%, 0.01% and 0.01% respectively for water, sediment, benthos, fish, and parasite. Biota-sediment accumulation factor (BSAF) for benthos, fish, and parasite were 0.01, 0.03 and 0.02, respectively, whereas the proportions of hydrocarbon utilizing bacteria in both sediment and water columns of Ilase were 0.18% and 17.6%, respectively, and those obtained from Ibasa were 0.001% and 0.03%. Among the PAH residues, naphthalene had the highest concentration. Ibasa had greater hydrocarbon utilizers and parasitic protozoa prevalence. This location had higher gill-induced malondialdehyde, catalase, glutathione peroxidase, glutathione and glutathione S-transferase. Also, it showed greater Histopathological Alteration Index (HAI) of 28.0 compared to Ilase community with HAI of 11.0. Generally, the sum of PAH concentrations in the sediment and water columns in both study sites fell within the EPA regulated limit (< 1000 ng/g). This indicates that the sediment and water on both sites were of moderate ecological risk. PAH residues accumulated in sediments, as well as in benthic invertebrates, get into bentho-pelagic host food chain and food webs; these could pose a significant risk to human health. As a result of this, continuous monitoring is highly advised.