Nematode as a biomonitoring model for evaluating ecological risks of heavy metals in sediments from an urban river

Heavy metals have attracted much attention due to their irreversibility, persistence, concealment and bio-accumulation. Biomonitoring method combined chemical analysis can be well evaluate health risks of heavy metals in the environment. In this study, eleven sediments and water samples were collected along Xihe River, which was polluted by heavy metals in Shenyang city of China. The content of multiple heavy metals in these samples was determined by inductively coupled plasma mass spectrometry. 18S rRNA gene sequencing was performed to identify the composition and diversity of nematodes in fine River sediments. The biological toxicity of water-soluble extracts from the samples was further assessed by referring to different endpoints of Caeno-rhabditis Elegans. The results indicated that the risk of heavy metals in Xihe River was high (potential ecological risk index = 308.75), in which Hg and Cd are the main contributing factors. The relative abundance of nema-todes complemented the chemical analysis result, Enoplida, Mononchida, Triplonchida, and Chromadorida nema-todes presented a significant positive correlation with the concentration of heavy metals. Specially, Chromadorida nematodes were sensitive to changes in heavy metals in Xihe River, which was significant positively correlated with As, Pb and V. Therefore, nematodes such as Chromadorida can be applied in environmental monitoring to evaluate the health risks of heavy metals.