Algal growth potential based nitrogen and phosphorus criteria for bloom control

High concentrations of nitrogen (N) and phosphorus (P) in aquatic systems can readily induce eutrophication, posing significant ecological and human health risks. Establishing scientifically sound N and P water quality criteria is therefore essential for effective water resource management and algal bloom mitigation. Current approaches to establishing lake nutrient criteria primarily rely on determining reference conditions, a method that faces practical limitations due to the pervasive pollution affecting most water bodies. To address this challenge, this study introduces an innovative methodology for deriving N and P criteria based on algal growth potential analysis, which establishes the theoretical minimum nutrient thresholds required for bloom formation.We selected and cultured twenty-three dominant algal species identified from documented bloom events to assess their growth potential. Under optimized cultivation conditions, we determined the maximum N and P yield coefficients for each species, from which we subsequently calculated species-specific N and P criteria based on predetermined bloom thresholds. Using species sensitivity distribution (SSD) analysis, we derived protective nutrient criteria corresponding to the 5th percentile hazard concentration: 0.204 mg/L for N and 0.006 mg/L for P. These values are notably more stringent than those established in European and American guidelines, as well as previous Chinese studies. This study thus establishes a novel scientific framework for developing water quality standards, particularly applicable to urban lakes receiving reclaimed water with high N and P concentrations. • The new N and P criteria deduction method is based on algal growth potential • Species sensitivity distribution model was used for criteria extrapolation • 23 dominant algal species were adopted according to the bloom outbreak data • Different species have dramatically distinct yield coefficients of N and P • The derived N and P criteria are 0.204 mg/L and 0.006 mg/L in this study