Shellfish are an important source of proteins, essential minerals, and vitamins vital for many coastal communities in Africa, however, consuming metal contaminated shellfish can pose health risks to humans. Using filter feeders and grazers as bioindicators, we investigated the trophic transfer of metals along the food web, their biomagnification/biodilution, non-carcinogenic and carcinogenic health risks associated with the consumption of shellfish at urbanised and non-urbanised (natural) sites along South Africa’s southeast coast. Filter feeders bioaccumulated/biomagnified elevated Cd, Co, Ni, As, Cu and Zn at urbanised sites in higher doses than grazers. Comparably, δ15N was enriched in samples from urban sites with the highest δ15N values being recorded in filter feeder and grazers. Ni, Pb, Cu and Zn showed significant trophic magnification (TMS > 1, p < 0.05), with Al, Cr, and As showing weak magnification, while Cd showed biodilution (TMS < 1). Considering elevated risk quotients (EDI, EWI, THQ, HI> 1) for Cr, Cd, Cu, and target carcinogenic risk (TCR >10–4) for As, Cd in filter feeders and grazers, this poses health concerns for the consumption of edible shellfish (e.g., mussels, oysters, and limpets) along this coastline. This study underscores the critical need to avoid consumption of metal contaminated shellfish to safeguard seafood security and protect the livelihoods of recreational and subsistence gatherers, particularly in the Global South. |
