Growth inhibition and toxic effects of microplastics on Chlorella vulgaris

Microplastics (MPs) are new pollutants that severely threaten the water environment. This study investigated the effects of three microplastics, namely polymethyl methacrylate (PMMA), polyvinyl chloride (PVC), and polystyrene (PS), on the growth, photosynthesis, biochemical composition, and antioxidant enzyme activity of Chlorella vulgaris. The results show that the average growth inhibition rate of PVC (1000 mg/L) is the highest (29.34 %), followed by PMMA (17.86 %), and PS (13.79 %). The small particle size and high concentration of microplastics are benefited to the inhibitory effect. The increase in soluble proteins within microalgae cells can enhance their water retention capacity and protect cell membranes from mechanical damage and lipid peroxidation caused by microplastics. The decrease in carbohydrate production can be attributed to a decrease in photosynthetic rate and overall physiological activity. The changes in superoxide dismutase and catalase activity can be seen as a defense mechanism for algae cells to maintain antioxidant system balance while removing excess reactive oxygen species.