Trophic transfer and biomagnification of four heavy metals in freshwater food web: a case study of Zhangze Lake

Heavy metals are a subject of widespread concern because of their persistence, potential toxicity, and accumulation in biological tissues. However, their biomagnification in food webs is still controversial and has not been studied in detail especially in freshwater ecosystems. This study investigated the trophic transfer and biomagnification of four heavy metals (Cu, Cd, Pb, and Hg) within the food web of the freshwater Lake Zhangze. The study showed that the trophic levels of aquatic consumers in the lake ranged from 2.00–4.53. The presence of Hg in sediments posed a strong ecological risk, and the integrated ecological risk was spatially reduced from the front of the dam to the tail of the reservoir. Planktivorous fish exhibited higher concentrations of Cu, Cd and Hg compared to other fish consumers. Heavy metals showed distinct bioaccumulation patterns within the food web, with Cu biomagnification primarily occurred at lower trophic levels, whereas Hg demonstrated biomagnification trends throughout the food web, while Cd and Pb rarely biomagnified within the food chain. Cu, Cd and Pb levels were effectively biodiluted with increasing biological trophic levels, whereas Hg levels increased with increasing trophic levels.