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Co-Exposure to Glyphosate and Polyethylene Microplastic Affects Their Toxicity to Chlorella vulgaris: Implications for Algal Health and Aquatic Risk
Summary
Researchers assessed the individual and combined toxicity of polyethylene microplastics and glyphosate to the microalga Chlorella vulgaris in acute and chronic exposures. The combination caused greater toxicity than either contaminant alone, particularly at chronic exposure durations, indicating synergistic effects relevant to agricultural runoff contamination.
Polyethylene microplastics (PE-MPs) and glyphosate (GLY) are widespread aquatic contaminants, but their combined effects on microalgae remain poorly understood. This study assessed the individual and joint toxicity of GLY and PE-MPs to the model microalga Chlorella vulgaris. Acute (3-day) and chronic (7-day) exposures were performed using GLY at 1-40 mg/L, alone or combined with PE-MPs (10 mg/L). A four-parameter log-logistic (4PL) model was applied to estimate median effect concentrations (EC50). After 72 h, the EC50 values were 9.77 mg/L for the GLY single system and 2.31 mg/L for the GLY-PE combined system, confirming enhanced toxicity in combined exposures. Co-exposure reduced pigment levels (chlorophyll a, chlorophyll b, and carotenoids) by up to 65% and significantly increased oxidative stress markers, including reactive oxygen species production and malondialdehyde accumulation, compared with single treatments. Antioxidant enzymes (superoxide dismutase and catalase) showed concentration- and time-dependent responses, indicating activation of cellular defense mechanisms. Scanning Electron Microscopy revealed PE-induced aggregation and structural damage to algal cells, particularly at higher GLY concentrations. These findings demonstrate that PE-MPs can amplify the toxic effects of GLY on microalgae and highlight the need for further studies at environmentally relevant concentrations and with different polymer types.
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