Abstract
ObjectiveThis 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.MethodsTwo 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.ResultsA 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).ConclusionThis 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.
Highlights
There is an increasing concern about environmental pollution of coastal ecosystems, as they are considered to be the most sensitive areas for the accumulation of toxic compounds because of the huge amount of anthropogenic discharge from human and industrial activities
Mugilis cephalus had the highest low molecular weight Polyaromatic hydrocarbon (PAH) than the other fishes while Saratherodon melanotheron recorded the highest concentration of the 4–6 rings PAHs
Dividing the sum of the high-density PAHs with the low-density PAHs gave the source index in water and sediment as 0.64 and 1.70 for the community and 22.31 and 1.16 for Ibasa community. This source index indicates that the PAH residues in the water and sediment in the Ibasa community are of the petrogenic source (> 0.1); this includes the sediment of the community site, but the Ilase community water medium is of the pyrogenic source
Summary
There is an increasing concern about environmental pollution of coastal ecosystems, as they are considered to be the most sensitive areas for the accumulation of toxic compounds because of the huge amount of anthropogenic discharge from human and industrial activities. The most important classes of environmental pollutants in the coastal area are the polycyclic aromatic hydrocarbons (PAHs) (Botello, Calva, & Ponce-Velez, 2001; Boonyatumanond, Murakami, Wattayakorn, Togo, & Takada, 2007; Gaspare, Machiwa, Mdachi, Streck, & Brack, 2009). They are found everywhere, derived from mainly anthropogenic sources (Woodhead, Law, & Matthiessen, 1999). They accumulate in sediments, aquatic pelagic and benthic food webs and pose a risk to human health (Baumard et al, 1998; Law & Klungsoyr, 2000; Abdolahpur Monikh, Hosseini, Kazemzadeh Khoel, & Ghasemi, 2014; Ayola, Olorunsanmi, & Oke, 2017)
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