Heavy metals bioaccumulation and its impact on fatty acids composition in the benthic crustacean mud crab (Scylla paramamosain) and associated human health risk.

Heavy metals (HMs) can alter fatty acid (FA) composition in aquatic organisms, but their effects on wild benthic crustaceans remain underexplored. This study quantified HMs accumulation in the gills and muscles of the mud crab Scylla paramamosain from three South China estuaries (Rongjiang, Huanggang, and Pearl River) and examined associations with FA profiles. HMs were consistently higher in gills than muscles, with females crabs accumulating significantly more HMs than males crabs. FA composition showed distinct sex-based patterns, with females having higher levels of saturated fatty acids (e.g., arachidic acid and stearic acid), while males were richer in omega-3 polyunsaturated fatty acids (e.g., EPA and DHA). Correlation analyses identified significant links between specific metals and FAs, such as arsenic (As) being positively correlated with palmitic acid, while mercury (Hg) and zinc (Zn) showed negative correlations with several FAs. These findings suggest that HMs accumulation influences FA composition in benthic crustaceans, reflecting complex pollutant-biota interactions. Human health risk assessment showed that daily and weekly intakes of copper (Cu) and iron (Fe) were within safe limits, but elevated cancer risk indices were observed for As, cadmium (Cd), and Cu, particularly in crabs from the Pearl and Huanggang estuaries. While hazard quotients were below 1, these findings indicate potential long-term cancer risk from regular mud crab consumption in these areas. This study highlights sex- and tissue-specific patterns of metal bioaccumulation and FA alterations, emphasizing the need for continued monitoring and management of metal pollution in estuarine ecosystems.