Ecological risk analysis and prediction of microplastics' effects on Microcystis aeruginosa in freshwater system: a meta-analysis approach

As emerging contaminants, micro/nano-plastics (MNPs) pose significant ecological risks to aquatic ecosystems. However, a systematic understanding of their impact on Microcystis aeruginosa-a globally prevalent cyanobacterium in harmful algal blooms-across multiple physiological levels remains limited. We develop an associative framework that identifies key correlations between MNP properties (size, degradability) and exposure conditions (concentration, time) with toxicological responses across four physiological systems in M. aeruginosa. Through a meta-analysis of 3,379 data points from 45 studies, we demonstrated that MNPs significantly inhibited growth (Hedges' g = -0.70 ± 0.34, p < 0.0001) and photosynthetic efficiency (g = -0.87 ± 0.38, p < 0.0001), while upregulating antioxidant activities (g = 0.37 ± 0.10, p < 0.0001) and microcystin production/release (g = 0.39 ± 0.17, p < 0.0001). Notably, our degradability-based classification indicated that petroleum-based microplastics (PBMs) and nanoplastics (NPs; ≤100 nm) were associated with stronger toxic effects in growth inhibition, membrane damage, and microcystin release than bio-based microplastics (BBMs) or larger particles. Dose-response patterns further showed concentration-dependent inhibition of growth and photosynthesis, with microcystin excretion peaking at 174.16 mg/L MNPs. Temporal dynamics revealed biphasic responses: photosynthetic recovery occurred at 3-7 days, while redox adaptation emerged after 7 days, suggesting stress acclimation mechanisms. Crucially, distance-based redundancy analysis (db-RDA) revealed that intracellular microcystin accumulation was strongly correlated with MNPs concentration, whereas extracellular release predominantly linked to particle size (threshold: <4.01 mm). These findings establish an integrated conceptual model that organizes observed associations between MNPs properties and specific toxicological pathways, and providing novel insights into bloom dynamics under plastic pollution.