Co-Exposure to Glyphosate and Polyethylene Microplastic Affects Their Toxicity to Chlorella vulgaris: Implications for Algal Health and Aquatic Risk

TL;DR

This study shows that combining glyphosate and polyethylene microplastics increases their toxicity to a type of algae, which could impact aquatic ecosystems.

Contribution

The study reveals that co-exposure to glyphosate and microplastics enhances toxicity to microalgae, a finding previously unexplored.

Findings

Combined exposure to glyphosate and polyethylene microplastics significantly increased toxicity to Chlorella vulgaris.

Co-exposure reduced pigment levels and increased oxidative stress markers in the algae.

PE-MPs caused structural damage to algal cells, especially at higher glyphosate concentrations.

Abstract

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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