Dynamics and Driving Mechanisms of the Regime shifts from Clear-Grass to Turbid-Algae Stable State in a Shallow Lake Ecosystem

Due to the limited availability of long-term monitoring data and the constraints of methods for validating theory of alternative stable states, the dynamics and cross-scale driving mechanisms of regime shifts in shallow lakes have not yet been systematically understood. Furthermore, relevant empirical case studies remain exceedingly scarce. Therefore, this study focuses on Gehu Lake, a typical shallow lake in China. A dataset of aquatic vegetation coverage (AV) and algal blooms area (AB) from 2000 to 2024 were constructed based on multi-parameter remote sensing inversion. By integrating historical observations, alternative stable states theoretical modeling and early warning indicators, this study reveals dynamics, hysteresis, and driving mechanisms of regime shifts. It was found that: 1) From 2000 to 2024, the AV and AB exhibited a significant spatiotemporal antagonistic relationship. The ecosystem underwent a complete shift from clear-grass stable state (Cgs) to turbid-algae stable state (Tas). 2) The mechanism of regime shifts aligns with the theory of alternative stable states, characterized by pronounced non-linearity and a significant hysteresis effect. 2007 marked the bifurcation point, preceded by brief "flickering" phenomenon between Cgs and Tas.3) The regime shifts is triggered by exogenous nutrient inputs, with the positive feedback mechanism of "reduced transparency-vegetation decline-algal outbreaks" progressively intensifying, ultimately surpassing ecological thresholds. This study presents an empirical case of regime shifts in shallow lakes, offering theoretical insights and practical guidance for ecosystem restoration globally.