Assessment of heavy metals and proximate composition of a jellyfish (Rhizostoma octopus Gmelin, 1791) from Cox's Bazar coast, Bay of Bengal, Bangladesh: Tracing contamination sources and human health risks

This study assessed the proximate composition and heavy metal (HM) contamination of the jellyfish Rhizostoma octopus collected from the Cox's Bazar coast, Bangladesh. To minimize post-mortem alterations, three specimens were collected alive from fishermen's nets near the shoreline. HM concentrations were determined using atomic absorption spectroscopy. The mean concentrations of metals and minerals decreased in the order: Na > Mg > K > Ca > Fe > Zn > Mn > Cu > Pb > Ni > Co > Cd > Cr > As. Proximate composition analysis (sun-dried weight basis) showed that ash was predominant (46.84-54.58%), followed by protein (25.79-27.76%), moisture (16.47-18.73%), carbohydrate (0.21-9.74%), and fat (0.46-0.79%). Principal component analysis identified two major components explaining most of the variance in metal contents, while hierarchical cluster analysis revealed similar accumulation patterns among metals. Health risk assessment suggested that individual target hazard quotient values for all metals were below 1, and the overall hazard index was also below 1, suggesting no significant non-carcinogenic risk. However, carcinogenic risk estimates were higher for children than adults, with Cd was estimated to exceed the USEPA acceptable threshold for children, showing a value of 2.48E-04. Despite the advantage of live sampling, the small sample size and limited spatial and temporal coverage restrict the representativeness of the results. Therefore, larger-scale and long-term studies are required to validate the safety of R. octopus for human consumption and to support its potential as a sustainable food resource within the blue economy.