Bioaccumulation and Health Risk Assessment of Heavy Metals in Seaweeds from the Gulf of Mannar, Southeast Coast of India.

Heavy metals are among the most prevalent pollutants in marine environments. Seaweeds, widely consumed as a coastal superfood, can accumulate these contaminants from anthropogenic inputs. In this study, 15 seaweed species from the Gulf of Mannar, Southeast coast of India, were analysed for four toxic metals to evaluate their bioaccumulation potential and associated human health risks. The results revealed that the green algae concentrated Zn > Cu > Pb > Cd, brown seaweed mainly concentrated Zn > Pb > Cu > Cd, and red seaweed showed Zn > Cu > Pb > Cd, respectively. In green seaweeds, Cd (0.88-1.99 μg/g), Cu (3.59-14.97 μg/g), Pb (1.71-13.71 μg/g), and Zn (1.82-18.19 μg/g) were recorded. Brown seaweeds showed Cd (0.97-3.63 μg/g), Cu (0.62-14.20 μg/g), Pb (1.37-13.37 μg/g), and Zn (3.91-13.32 μg/g). Red seaweeds contained Cd (0.23-3.61 μg/g), Cu (1.24-18.71 μg/g), Pb (0.79-6.37 μg/g), and Zn (0.33-26.21 μg/g). Seasonal distribution was uniform (p < 0.05), and interspecies differences were not significant. Bioaccumulation factor (BAF) analysis revealed marked differences in metal uptake among seaweeds. Additionally, brown and red seaweeds showed the highest BAF values for Cu, Pb, Zn, and Cd, highlighting their strong bioremediation potential, while green seaweeds showed low BAF values, except Cd, in Codium tomentosum and Caulerpa peltata. Health risk assessment (HQ/HI < 1) confirmed that all groups were safe; however, excessive consumption of green seaweeds may pose risk.