Climate warming and nutrient depletion are altering the spatiotemporal dynamics of microcystin in lake Taihu

Climate warming and eutrophication are transforming cyanobacterial bloom dynamics and microcystin (MC) release in lacustrine systems, though the underlying drivers and future risks remain not fully elucidated. Through integrated analysis of historical data (2008-2019) and field sampling (2023-2024) in Lake Taihu, we revealed a significant decline in annual MC concentrations (peak in 2008-2009), with high-pollution zones shifting from northern bays to eastern lake regions (2008-2019 to 2023). Health risk assessments consistently indicated higher risks for children than for adults, and ecotoxicity analysis revealed benthic organisms as relatively sensitive bioindicators. Further studies demonstrated that temperature shows a significant positive association with MC concentrations, a relationship that may be partly mediated by its correlation with chlorophyll-a, whereas total nitrogen is associated with higher MC levels and may exhibit links through cascading correlations involving pH and chlorophyll-a. Predictive modeling estimated that MCs exceeded 1 μg/L when water temperature exceeded 35 °C under nitrogen loads (0.5-1.5 mg/L or 2.0-2.5 mg/L). Estimates derived from linear extrapolation indicate that, under the modeled future climate conditions (2028-2029; 2033-2034), warmer winters and summers may advance the phytoplankton biomass peak by roughly three months. This is expected to intensify toxic cyanobacterial dominance, resulting in an estimated 30-80 % rise in MC release, thereby intensifying ecosystem toxicity and human health exposure risks in Lake Taihu. This work provides priority intervention strategies for mitigating toxins in eutrophic lakes.