Toxicity risks associated with trace metals call for conservation of threatened fish species in heavily sediment-laden Yellow River

Trace metals and metalloids in aquatic ecosystems may lead to adverse effects on the survival of fish, especially in the sensitive life stages of vulnerable species. It is still unknown whether threatened fish species in the heavily sediment-laden Yellow River are exposed to toxicity risks associated with multiple trace metals. Herein, we analyzed the concentrations of trace metals in aquatic environmental media and fish tissues across the Yellow River mainstream and assessed the level of metal toxicity to threatened fish. Significantly different concentra-tions of trace metals in fish tissues were measured between at least two categories among near-threatened, vulnerable, endangered, and critically endangered fish. No metal showed a higher concentration in demersal fish than in pelagic fish. Substantially low metal toxicity was observed for the gill of Rhinogobio nasutus (near -threatened) in the upper reaches, as well as for the gill and liver of Silurus lanzhouensis (endangered) in the middle reaches. High contents of suspended sediment in water and high metal concentrations in sediment and suspended matter could influence the survival and reproduction of fish, especially those already with threatened status.

Automated summary

Trace metals and metalloids in aquatic ecosystems can have adverse effects on fish survival, especially during vulnerable life stages. It is still unclear if threatened fish species in the heavily sediment-laden Yellow River are at risk of toxicity from multiple trace metals. In this study, we analyzed the concentrations of trace metals in the river's water and fish tissues, and evaluated the metal toxicity levels for threatened fish. We found significant differences in trace metal concentrations among different threat categories of fish, and observed lower metal toxicity in certain species in specific reaches of the river.