Toxic effects and metabolic response mechanisms of amino-modified polystyrene nanoplastics and arsenic on Microcystis aeruginosa

Abstract

Plastic contamination poses an increasing threat to our environment, particularly with the accumulation of nanoplastics (NPs, <1 µm) in aquatic systems. Amino-modified polystyrene nanoplastics (PSNPs-NH₂), due to their high reactivity and biocompatibility, may exert toxic effects on aquatic organisms like cyanobacteria. Microcystis aeruginosa (M. aeruginosa), a common cyanobacterium widely distributed in aquatic ecosystems, plays a crucial role as a primary producer and is sensitive to NPs and arsenic (As) contamination. This work examined the effects of PSNPs-NH₂ alone (PS), As alone (As), and co-exposure (AP) on Microcystis aeruginosa using exposure experiments, three-dimensional excitation-emission matrix (3D-EEM) fluorescence spectroscopy, and metabolomics. Results indicated that amino-modified polystyrene nanoplastics significantly inhibited M. aeruginosa growth, with chlorophyll a content reduced by 12.28%-12.96% at high doses amino-modified polystyrene nanoplastics increased intracellular O₂·⁻ levels by 5.10% - 15.75%, while Arsenic significantly elevated H₂O₂ levels by 2454.92%, which decreased by 74.61% - 87.76% under AP. Arsenic and AP increased intracellular and extracellular microcystin. Metabolomic analysis indicated that amino-modified polystyrene nanoplastics upregulated amino sugar metabolism to enhance extracellular polymeric substances (EPS) secretion, while AP activated fatty acid degradation to cope with stress. In summary, the research reveals the multi-level toxic impacts of PSNPs-NH₂ and arsenic, alone and co-exposure on Microcystis aeruginosa, providing scientific underpinnings for evaluating the potential threats of nanoplastics and metal (loid) co-exposure to aquatic ecosystems.