Application of Biotic Ligand Model in Predicting Copper Acute Toxicity to Carp (Cyprinidae)

Three representative species of Cyprinidae fishes (Aristichthys nobilis, Ctenopharyngodon idellus, and Cyprinus carpio), which are abundant in Chinese surface waters, were studied to determine their sensitivity to copper (Cu) in acute exposures. We first performed acute toxicity tests to determine the Cu LC₅₀ value for each species in water with varying characteristics. The biotic ligand model (BLM) was then calibrated using the toxicity data for these species together with binding properties specific to Cu. The BLM calibration involved the calculation of the level of Cu accumulation in the gills that resulted in 50% lethality (i.e., LA₅₀). The LA₅₀ values for A. nobilis, C. idellus and C. carpio were 5.16, 11.60 and 9.00 nmol g^-1. The model calibrated to these data was improved by adjusting the Cu-proton exchange constant (pK _CuHA-A) and dissolved organic carbon (DOC) to values of 1.84 and 4.67E-3 mol g^-1, respectively. The calibrated Cu-BLM was validated for these three common fish species by comparing predicted and observed LC₅₀ values, which were in agreement to within a factor of 2. The results of this study provide an important contribution to ecological risk assessment and establishment of water quality criteria for Cu in China.