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Polystyrene Microplastics Induce Photosynthetic Impairment in Navicula sp. at Physiological and Transcriptomic Levels
Summary
Researchers exposed freshwater diatom algae to polystyrene microplastics and found significant damage to their photosynthetic capacity within 24 to 48 hours. The microplastics reduced chlorophyll content, damaged cell membranes, and triggered oxidative stress responses, with gene analysis revealing disruption of key pathways related to photosynthesis and carbon fixation. The findings suggest that microplastic pollution in freshwater environments could impair the ability of algae to produce oxygen and support aquatic food webs.
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<sub>2</sub>) affect physiology and gene expression using the freshwater alga <i>Navicula</i> sp. as the test species. After exposing <i>Navicula</i> sp. to high PS-NH<sub>2</sub> concentrations for 24 h, growth was inhibited, with the most significant effect seen after 48 h. Increasing PS-NH<sub>2</sub> 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<sub>2</sub> 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<sub>2</sub> also affected the gene expression of <i>Navicula</i> 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.
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