Impacts of Inflow Loadings from Heavy Rainfall on Cyanobacteria Overgrowth in Nitrogen-Limited Reservoirs through Field Observation and Numerical Simulation

This study presents significant insights into the impact of nitrogen and phosphorus inflow loadings from agricultural activities on phytoplankton proliferation in a hypertrophic reservoir. Over two years, the study meticulously examined seasonal variations in phytoplankton, the dominance of algae species, and nitrogen and phosphorus levels in a reservoir prone to cyanobacterial blooms. The findings revealed that the reservoir was hypertrophic under nitrogen limitation, with temporal nitrogen loadings being the primary cause of algal abnormalities. Cyanobacteria, particularly sensitive to temporary nitrate-nitrogen increases triggered by heavy rainfall, dominated during the study period. A robust ecosystem model, validated through observational data, showed good reproducibility of results. It successfully anticipated shifts in phytoplankton growth patterns, successfully replicating the abnormal proliferation of several algae species. By conducting different nutrient loading scenarios, the research highlighted the crucial role of nitrogen reduction in curbing phytoplankton growth, especially in nitrogen-limited reservoirs. In environments facing severe nitrogen limitation, a simplified ecosystem model proved valuable, aiding in predicting seasonal phytoplankton changes. This study underscores the necessity of accurately identifying limiting factors and implementing targeted strategies to effectively mitigate algal blooms in eutrophic water bodies.