Interactive effects of amine-modified nanoplastics and nitrogen source on Microcystin-LR synthesis and release in Microcystis aeruginosa.

Concern over the nanoplastics (NPs) pollution in aquatic environment is increasing. However, the potential effects of different nitrogen sources at environmentally relevant concentrations and NPs on Microcystin-LR (MC-LR) in Microcystis aeruginosa (M. aeruginosa) are still unclear. Results demonstrate that during both acute (4 days) and long-term (10 days) exposure, MC-LR synthesis (27.86% and 59.18%) and release (21.79% and 76.68%) were significantly exacerbated by amine-modified polystyrene NPs (PS-NH2 NPs) under high concentration (5 mg-N/L) arginine treatment, compared with nitrate and leucine treatments. Mechanistically, under high concentration (5 mg-N/L) arginine treatment (1) PS-NH2 NPs exposure promoted algal nitrogen consumption efficiency, together with an increase of NPs internalization and cell membrane permeability; (2) metabolomic and transcriptomic results suggested that alterations in carbon and nitrogen metabolism, precursor availability, and membrane integrity may contribute to the increased MC-LR synthesis and release under PS-NH2 NPs exposure; and (3) stable isotope experiment verified that PS-NH2 NPs activated the precursor substances of MC-LR synthesis. The elevated temperature and light intensity further altered the effect of PS-NH2 NPs on MC-LR synthesis. These findings deepen our understanding of the interactive effect of NPs and nitrogen sources on M. aeruginosa.