Phenanthrene Amplifies Microcystin-Induced Toxicity in the Submerged Macrophyte Vallisneria natans
2025
Xiang Wan | Yi Zhang | Yucong Li | Fei Yang | Liqiang Xie
Microcystin&ndash:LR (MC-LR) and phenanthrene (Phen), which commonly co-occur in eutrophic waters, have been extensively studied as individual contaminants, but their combined ecotoxicological effects on submerged macrophytes remain unclear. In this study, we examined the individual and combined toxicity of MC-LR (2, 10, 50, 250, and 1000 &mu:g/L) and Phen (0.2, 1, 5, 25, and 100 &mu:g/L) on the submerged macrophyte Vallisneria natans over a 7-day exposure. Key toxicity biomarkers, including growth, photosynthetic efficiency, and antioxidant responses (catalase, superoxide dismutase, glutathione S-transferase, and malondialdehyde), were evaluated. The results showed that high concentrations of each contaminant alone (MC-LR &ge: 1000 &mu:g/L: Phen &ge: 100 &mu:g/L) significantly inhibited growth and reduced photosynthetic efficiency. In contrast, synergistic toxicity was observed at much lower combined concentrations (&ge:50 + 5 &mu:g/L), with effects substantially exceeding those of individual exposures. Co-exposure intensified antioxidant activity, but it was insufficient to mitigate oxidative damage. Notably, Phen at concentrations above 25 &mu:g/L significantly enhanced the bioaccumulation of MC-LR in V. natans. These findings demonstrate that environmentally relevant mixtures of MC-LR and Phen induce remarkable toxicity even at concentrations where individual compounds show negligible effects. The results highlight that co-existing cyanotoxins and polycyclic aromatic hydrocarbons may present greater ecological risks than predicted from single-contaminant assessments, underscoring the need to update current ecological risk frameworks for the accurate evaluation of complex pollution scenarios in freshwater systems.
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