Unraveling the toxic mechanisms of microplastics in aquatic ecosystem: A case study on Vallisneria natans and Myriophyllum verticillatum

Microplastics (MPs) have become ubiquitous pollutants in diverse ecosystems, with aquatic environments increasingly identified as major sinks. Nevertheless, the ecological risks and toxic effects of MPs on submerged macrophytes remain poorly understood. This study examined the impacts of three common MPs including polyvinyl chloride (PVC), polystyrene (PS) and polyethylene (PE) at varying concentrations (10 mg/L; 50 mg/L; 100 mg/L) on two submerged plant, Vallisneria natans (V. natans) and Myriophyllum verticillatum (M. verticillatum). The results demonstrated that MPs significantly inhibited the growth of submerged macrophytes, triggered antioxidant responses, and caused membrane damage. Metabolomics analysis revealed that PVC MPs disrupted key metabolic pathways, including pyrimidine metabolism, alanine, aspartate, and glutamate metabolism, as well as β-alanine degradation in V. natans. Furthermore, MPs reduced dissolved oxygen (DO) and oxidation-reduction potential (ORP) levels in the water, promoting the proliferation of Bacteroidetes, Firmicutes, and Chloroflexi in sediments and biofilms. These findings suggest that the toxic mechanisms of MPs on submerged macrophytes primarily involve water quality degradation, shifts in the abundance of dominant microorganisms in sediments and biofilms, and the induction of physiological and metabolic disturbances within the plants. The study provides new insights into the broader ecological implications of MPs in aquatic ecosystems.