Bioaccumulation of toxic elements in two shark species from the United Arab Emirates waters of the Arabian Gulf

Marine ecosystems are threatened by pollution input from anthropogenic sources. We evaluated 19 elements in the gills, liver and muscle of milk sharks (Rhizoprionodon acutus) and spot-tail sharks (Carcharhinus sorrah) from Abu Dhabi and Dubai, United Arab Emirates. Cadmium (0.04–16.12 mg kg⁻¹), copper (0.59–0.74 mg kg⁻¹), mercury (0.10–15 0.68 mg kg⁻¹) and iron (122.97–355.48 mg kg⁻¹) concentrations in milk sharks from three tissue types were at levels that exceeded maximum permissible levels for human consumption. Overall toxicity, measured using the metal pollution index, indicated high toxicity in milk sharks from Dubai. We report Cd transfer from milk shark adults to pups. Generally, differences in concentrations of specific heavy metals could be due to different rates at which these are bioaccumulated in the two species of sharks. Increasing concentrations of heavy metals in marine species is a matter of great concern for species in upper trophic levels of marine food webs. Concentrations of Cd, Cu and Hg above maximum permissible limits for human consumption also raises concerns on their impact on human health.