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Calcium-mediated mitigation of aged nanoplastic-induced stress in microalgae: Insights into photosynthesis, energy metabolism, and antioxidant defense from physiological and multi-omics analyses
Summary
Scientists found that tiny plastic particles (nanoplastics) severely damage microalgae, which are important organisms used to clean wastewater before it enters our water supply. However, adding calcium to the water protected the microalgae from this plastic pollution and helped them continue removing harmful substances from wastewater. This research suggests calcium could help maintain clean water treatment systems even as plastic pollution increases in our environment.
Aged nanoplastics (ANPs) have emerged as a significant risk factor for microalgal wastewater treatment. However, Ca appearing to have a moderating effect on this potential threat. This study investigated the response of Chlorococcum sphacosum to ANPs exposure and the protective role of Ca through integrated physiological and multi-omics analyses. Exposure to 1 mg/LANPs reduced the removal of NH-N, TP, and COD by an average of 17.2%. Key physiological parameters were also suppressed, with biomass, chlorophyll a content, and photosynthetic efficiency (Fv/Fm) decreasing on average by 44.2%. Transcriptome analysis revealed that genes related to photosynthesis and energy metabolism were downregulated on average by 73.4%, highlighting the molecular basis for disrupted energy homeostasis and redox balance. Metabolomic analysis confirmed that key antioxidant metabolites, including glutathione, l-glutamic acid, linoleic acid, putrescine, and azelaic acid, decreased on average by 62.6%. These disturbances progressively caused structural deterioration, characterized by thylakoid disassembly, plasmolysis, and cell wall degradation, which impaired cellular activity and physiological function. Notably, 10 mM Ca supplementation effectively counteracted these adverse effects. Ca supplementation improved nutrient removal, restored physiological performance, increased antioxidant levels, mitigated transcriptional repression of photosynthetic and energy metabolism genes, and reversed the suppression of antioxidant biosynthesis. Overall, this study systematically elucidates the Ca-mediated resilience network in microalgae under ANPs exposure. These findings provide mechanistic insights and practical strategies for sustaining microalgae-based wastewater treatment in the presence of nanoplastic contamination.