Trophic relationships and health risk assessments of trace metals in the aquaculture pond ecosystem of Pearl River Delta, China

► Trace metals concentrations in organisms and sediments collected from fish ponds. ► Cr, Cd, Pb and Ni were the most available metals in pond sediment. ► Omnivorous species accumulated more metals from sediment than the carnivorous. ► The trace metals were not biomagnified through the pond food chains. Cadmium, lead, zinc, Chromium, copper, nickel and manganese in sediments and in aquatic organisms were collected from the aquaculture pond ecosystem of the Pearl River Delta (PRD), China and analyzed to evaluate bioaccumulation and trophic transfer in food chains, as well as the potential health risk of exposure to the Hong Kong residents via dietary intake of these aquatic products. The results revealed that based on the biota–sediment accumulation factor, omnivorous fish and zooplankton accumulated more trace metals from sediment than carnivorous fish. Concentrations of seven trace metals in aquaculture pond of PRD significantly decreased with increasing trophic levels, showing that these trace metals were trophically diluted in predatory and omnivorous food chains. The hazard index values of all fish species were smaller than 1 for adults and children, indicating there was no health risk from the multiple metals via ingestion of the freshwater fish for the inhabitants.