Differences in metal compositions and concentrations of sympatric predatory fish and squid from the South Atlantic Ocean

Metals occur naturally in the environment and in organisms. Organisms at higher trophic levels may contain metals at elevated concentrations, as a result of accumulation from anthropogenic and natural sources, potentially making them more susceptible to detrimental effects, as well as passing them on to consumers. The concentrations of thirty metals were quantified in hake (Merluccius capensis), kingklip (Genypterus capensis), monkfish (Lophius vomerinus) and chokka (Loligo reynaudii) collected from the South Atlantic Ocean of South Africa in February 2017 and February 2019, using inductively coupled plasma mass spectrometry. Metal concentrations and composition in nektobenthic chokka differed significantly from the three demersal fish predators (hake, kingklip, and monkfish). Demersal fish metal concentrations and relative pattern compositions (fingerprints) were similar. Because the samples were collected within an 80 km radius, the differences are likely as a result of a combination of factors, such as diet, habitat (depth), and differences in the physiological regulation of metals between cephalopods and fish, rather than location. Based on South African estimated daily intake, total hazard quotient and European Union limits for mercury, cadmium and lead, these four economically important species from the South Atlantic Ocean are safe for human consumption. Plankton, herbivorous marine species, and larger predators, such as sharks and dolphins, should be studied to obtain further insight into metals as baseline for monitoring possible future pollution and effects from climate change, trophic transfer, toxic effects, and human consumer safety.