Prioritizing remediation actions and identifying appropriate restoration goals: Findings from four representative eutrophic lakes along the Yangtze River, China

Four representative eutrophic lakes in the Yangtze River Basin, China: Dianchi Lake (Yungui Plateau), Chaohu Lake, Gehu Lake, and Dianshanhu Lake (Eastern Plateau). This study analyzes 25-year time-series data of total phosphorus (TP) and chlorophyll-a (Chla) to investigate recovery trajectories and ecological resilience following eutrophication control measures. Using the Filtering Trajectory Method (FTM) and Double Probability Method (DPM), we examine the dynamic relationships between Chla and TP, assess phosphorus utilization efficiency (ETP), and estimate dynamic TP carrying capacities (TPa) under varying environmental conditions. Analysis of recovery trajectories revealed heterogeneous Chla–TP relationships, ranging from significant to non-significant correlations across the lakes. Temperature significantly influenced phosphorus use efficiency (ETP) variations between the Yungui Plateau and Eastern Plateau lakes, highlighting the role of regional hydroclimatic conditions in shaping nutrient-algae dynamics. Dynamic estimates of total phosphorus carrying capacity (TPa) demonstrated that current uniform nutrient standards (50 μg/L) are insufficient for most lakes, and stricter, lake-specific thresholds (e.g., 15 μg/L for Dianchi) are required to achieve desired water quality outcomes. An ecological resilience assessment framework was developed, linking trajectory slopes to ecosystem sensitivity and critical ETP values to resistance against algal growth. These region-specific hydrological insights provide a scientific basis for adaptive nutrient management and long-term monitoring strategies in the Yangtze River Basin and similar eutrophic freshwater systems globally. • Recovery trajectories differ among four Yangtze River lakes. • Chla-TP correlation non-significant (p > 0.05) in two lakes during recovery. • Temperature drives ETP differences between plateau lakes. • Dynamic TP carrying capacities suggest stricter restoration targets. • Ecological resilience framework aids lake restoration assessment.