Establishing Nutrient Criteria in Nine Typical Lakes in China: A Conceptual Model

Nutrient criteria can provide technical support and management decisions information for avoiding over‐ and under‐protection of lakes. Integrating a conceptual model with multiple nutrient changepoints by three non‐linear statistical methods (classification and regression tree model, deviance reduction method, and Bayesian changepoint method) was used to determine the nutrient criteria for nine typical lakes in China differing by specific disturbance degrees and trophic status. Based on the similar impairment levels of nutrient changepoints, the studied lakes were classified into three types roughly including clean lakes, slightly altered lakes, and degraded lakes. For clean lakes, the changepoints were directly used as nutrient criteria (0.005–0.100 mg/L total phosphorus and 0.570–0.600 mg/L total nitrogen). For slightly altered and degraded lakes, due to ecological resilience, the target nutrient criteria should be lower than that of reference lakes inferring from the rationale of “space‐for‐time substitution.” The percentages of decline at changepoints (5, 10, and 20%) are suggested in light of chlorophyll a response criterion limits (2, 5, and 10 µg/L) for ensuring the safety of drinking water. The conceptual model used to address ecological succession along the gradient of disturbance degrees, is applicable to establish nutrient criteria in other lake ecosystems.