Effects of Uranium Exposure Combined with Elevated Temperature on the Growth of Microcystis aeruginosa and the Synthesis of Microcystins

This study explores the combined effects of elevated temperature and radioactive uranium contamination on Microcystis aeruginosa growth and toxicity synthesis, aiming to inform responses to global climate change and freshwater pollution. By simulating elevated temperature conditions and varying uranium concentrations, we assessed the comprehensive impact on Microcystis’ physiological and ecological traits. Results showed significant alterations in freshwater chemistry: pH decreased (2.62–7.87%), dissolved oxygen increased (9.21–15.78%), and conductivity rose (14.58–9.69%). Elevated temperature combined with uranium boosted Fv/Fm (Maximum Quantum Yield of PSII) (4.37–23.47%), Pi-ABS (Photosynthetic Active Radiation absorbed by Antenna Chlorophyll per Reaction Center in PSII) (58.89–78.93%) and OD680 (Optical Density at 680 nm) (15.69–20.37%), while reducing DIO/RC (Dissipation per Reaction Center in PSII Electron Transport Chain) (10.75–33.69%), indicating growth promotion. Metabolomics revealed 2.05-fold upregulation of deoxyinosine and 0.7–3.38-fold downregulation of amino acid metabolites, altering primary pathways, inhibiting key amino acid metabolism, and reducing microcystin synthesis. This underscores the complex regulation of elevated temperature and uranium on algal growth and toxicity, emphasizing the need to address their potential threats to freshwater ecosystems.