Trophodynamics and health risk assessment of heavy metals in seafood from a tropical estuary in the gulf of Guinea

Seafood is an essential protein source for coastal communities. However, they can accumulate heavy metals from human activities which could pose a potential health risk to consumers. In this study, we investigated the distribution, bioaccumulation, trophic transfer and potential human health risk of heavy metals in sediments, shell and fin fish collected from the Escravos Estuary in southern Nigeria. Heavy metals (Ni, Cd, V, Pb and Cu) in sediments, periwinkles and tongue soles from the two study sites were lower than the permissible limits for fishery products. The metal distribution in fish tissues was in the decreasing order of liver > gills > muscles > gonads > rest of the fish. Moderate to high BSAF (>1) was reported for Cd, Pb and Cu. All the studied metals, except Pb, showed evidence of biomagnification from periwinkle to tongue sole. The estimated daily intake (EDI) and hazard ratio (HR) for metals in periwinkles from both study sites were lower or within the USEPA reference doses (RfD) for the respective daily intake and HR value < 1, except for Cd, V and Pb for children. In contrast, EDI values in the muscle of tongue soles were higher than the RfD values for heavy metals except for Ni and Pb, whereas HR values > 1 except for Ni, Cd and V. In the whole fish, EDI and HR values were disproportionately high in both study sites with higher values reported for children. This study provides the first insights on the trophic transfer and risk assessment of heavy metals from petroleum and gas operations impacting the Escravos Estuary and the implications to public health.

Metal composition of arrow squid (Nototodarus sloanii [Gray 1849]) from the Chatham Rise, New Zealand: implications for human consumption

Cephalopods are important in the diets of humans and many other apex predators, and can play an important role in the bioaccumulation of metals. In this study, metal concentrations were analysed in the commercially and ecologically important southern arrow squid, Nototodarus sloanii (Gray 1849), from a heavily targeted fisheries area on New Zealand's Chatham Rise. A variety of tissue types were compared in order to assess the bioaccumulation in edible tissues (mantle and arms) and other organs (digestive gland, kidney, and hearts). Although metal concentrations varied among tissue types, the highest concentrations were found in the digestive gland (for Cd, Cu, Fe, Ni, Zn) and branchial hearts (for Cr, U). We report the first Cd concentrations for N. sloanii from the Chatham Rise, with mean values of 3.11 μg. g^-1 in the mantle and 102.53 μg. g^-1 in the digestive gland. Our data suggest that concentrations observed in the mantle tissue (which forms the majority of the muscle tissue) and digestive gland (the primary organ for metal accumulation) can be used to estimate the animal's total body burden for all metals analysed. The toxicological and dietary consequences for predators (including humans) feeding on arrow squid can be inferred from measurements of mass and metal concentration in these tissues. Arrow squid represent an important vector for Cd transfer within the pelagic Chatham Rise food web. These are the first recorded baseline data for metal concentrations for any squid in this oceanic region.