Adaptive physiological responses of Chlorella pyrenoidosa under long-term polystyrene nanoplastic exposure

Résumé fourni par la source

Nanoplastic pollution is an emerging threat to edible freshwater microalgae, but long-term physiological responses of Chlorella pyrenoidosa are poorly understood. In a 111-day cultivation study, we investigated algal acclimation to polystyrene nanoplastics (PS-NPs) at three sizes (50, 200, 500 nm) and three concentrations (10, 50, 100 mg/L). PS-NPs delayed exponential growth, with larger particles peaking 18 days later than controls, while stationary-phase biomass did not differ from controls, indicating adaptation. Lag phase uniformly suppressed photosynthetic pigments and cell viability. In the exponential phase, particle size served as the dominant regulatory factor, with concentration exerting interactive effects, though a few indicators were regulated primarily by concentration. In stationary phase, small PS-NPs generally stimulated most physiological markers, whereas larger particles caused sustained inhibition. Exceptions included carotenoids, which remained persistently suppressed across all treatments, and soluble protein, which returned to control levels. Carotenoids thus serve as sensitive chronic stress biomarkers. Stress-induced extracellular polysaccharide secretion increased over time in size- and dose-dependent ways, promoting heteroaggregation with PS-NPs, as verified by SEM and Py-GC/MS. Zeta potential gradually converged toward control values over cultivation, confirming that heteroaggregation facilitated PS-NP adsorption and reduced their impact on system stability. Small 50 nm particles elicited mild, reversible suppression of cell viability that was offset by metabolic compensation, whereas 500 nm particles caused persistent growth inhibition mainly through sustained light attenuation. Although tested concentrations exceed typical environmental levels, observed adaptive recovery reveals detoxification mechanisms employed by C. pyrenoidosa under chronic nanoplastic stress.

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