Application\nof the Biological Toxicity Effect Ratio\n(BER) Method for Advancing Water Quality Criteria Derivation

Water quality criteria (WQC) serve\nas a scientific foundation for\npollutant risk assessment and control in aquatic ecosystems. The development\nof regionally differentiated WQC tailored to specific regional characteristics\nhas become an emerging trend. However, the current WQC is constrained\nby a lack of regional species toxicity data. To address these limitations,\nthis study proposes the biological toxicity effect ratio (BER) method,\nwhich indirectly reflects the toxicity sensitivity of the overall\naquatic ecosystem through the toxicity information on a limited number\nof species, enabling rapid WQC prediction. Using the established WQC\nin China and the USA as a case study, we combined mathematical derivation\nand data validation to evaluate the BER method. Among various species-taxon\ngroups of freshwater organisms, planktonic crustaceans demonstrated\nthe highest predictive accuracy. Our analysis further revealed that\nspecies toxicity sensitivity and regional variability jointly influence\nthe prediction accuracy. Regardless of the evaluation indexes, planktonic\ncrustaceans emerged as the most suitable species-taxon group for the\nBER method. Additionally, the BER method is particularly applicable\nto pollutants with conserved mechanisms across species. This study\nsystematically explores the feasibility of using the BER method and\noffers new insights for deriving regionally differentiated WQC.