Acute Toxicity of Nickel to Daphnia magna: Validation of Bioavailability Models in Japanese Rivers

The ecotoxicity of nickel depends on water quality characteristics such as pH and dissolved organic carbon. Bioavailability models to predict nickel toxicity have been developed for and validated in European natural waters. In this study, we examined the acute toxicity of nickel to the strain of Daphnia magna that is used for toxicity tests in Japan, using water samples from five Japanese rivers. Based on the results of these toxicity tests, we examined the predictive capacity of the bioavailability model for acute nickel toxicity to D. magna and validated the model. The 50% effect and lethal concentrations (EC50 and LC50) of dissolved nickel for D. magna ranged from 0.52 to 4.0 mg/L and from 0.62 to 5.3 mg/L, respectively. Our results indicate that acute nickel toxicity varied as a result of the different water quality conditions in Japanese rivers. The bioavailability model predicted EC50 and LC50 values in water samples from Japanese rivers by errors more than a factor of 2, while the bioavailability models validated with the results of our toxicity tests were able to accurately predict these values with errors less than a factor of 2. Therefore, our results indicate that the bioavailability model validated using the results of the toxicity tests conducted using Japanese water samples could accurately predict acute nickel toxicity to the strain of D. magna.