Polystyrene Microplastics Induce Photosynthetic Impairment in sp. at Physiological and Transcriptomic Levels.

The rising concentration of microplastics (MPs) in aquatic environments poses increasing ecological risks, yet their impacts on biological communities remain largely unrevealed. This study investigated how aminopolystyrene microplastics (PS-NH) affect physiology and gene expression using the freshwater alga sp. as the test species. After exposing sp. to high PS-NH concentrations for 24 h, growth was inhibited, with the most significant effect seen after 48 h. Increasing PS-NH concentrations reduced chlorophyll content, maximum photochemical quantum yield (Fv/Fm), and the photochemical quenching coefficient (Qp), while the non-photochemical quenching coefficient (NPQ) increased, indicating a substantial impact on photosynthesis. PS-NH exposure, damaged cell membrane microstructures, activated antioxidant enzymes, and significantly increased malondialdehyde (MDA), glutathione peroxidase (GPX), and superoxide dismutase (SOD) activities. Transcriptomic analysis revealed that PS-NH also affected the gene expression of sp. The differentially expressed genes (DEGs) are mainly related to porphyrin and chlorophyll metabolism, carbon fixation in photosynthesis, endocytosis, and glycolysis/gluconeogenesis. Protein-protein interaction (PPI) analysis revealed significant interactions among DEGs, particularly within photosystem II. These findings shed insights into the toxic mechanisms and environmental implications of microplastic interactions with phytoplankton, deepening our understanding of the potential adverse effects of microplastics in aquatic ecosystems.