Excessive nitrogen (N) loading in aquatic ecosystems, driven by global fertilizer overuse, poses escalating threats to ecological balance. This study synthesizes a decade of multidisciplinary research on the ecological consequences of elevated N levels in shallow lakes, integrating long-term field experiments (experimental ponds/tanks) and short-term laboratory assays. Key findings reveal: (1) Dual role of nitrogen forms in sediment phosphorus (P) dynamics: High nitrate (NO₃⁻) and urea suppress P release via enhanced redox potential under N-limited conditions but stimulate it through phytoplankton biomass proliferation. Conversely, ammonium (NH₄⁺) promotes P release via oxygen depletion during oxidation, alkaline phosphatase induction, and sediment acidification. (2) Field resilience of aquatic organisms: Fish and zoobenthos exhibit higher ammonia (NH₃) tolerance in natural settings compared to lab conditions, attributed to ecological buffering (e.g., plant/sediment adsorption, NH₃ volatilization, nitrification-denitrification cycles) and organismal adaptations (e.g., dietary detoxification). Dynamic fluctuations in pH and temperature further mitigate NH₃ toxicity. (3) Macrophyte vulnerability: Submerged macrophytes display seasonal resilience, with canopy-forming species outperforming rosette types during rapid growth phases. However, prolonged N exposure precipitates population collapse, underscoring the transient nature of such tolerance. These insights advance mechanistic understanding of N-driven eutrophication and stress the urgency of adaptive management strategies to curb nitrogen emissions in freshwater ecosystems.