The effect of pH on chronic zinc toxicity differs between daphnid species: Development of a preliminary chronic zinc Ceriodaphnia dubia bioavailability model.

In the present study, we observed that the chronic Zn Daphnia magna biotic ligand model (BLM) could not accurately predict the chronic Zn toxicity to Ceriodaphnia dubia in a series of (modified) field waters, although the intrinsic sensitivities of the D. magna BLM were specifically calibrated on the sensitivity of C. dubia. Moreover, it was observed that the D. magna BLM underestimated the effect of pH on the toxicity of the free Zn ion. A preliminary species-specific chronic Zn C. dubia bioavailability model was developed based on the data. The preliminary Zn C. dubia bioavailability model was shown to predict Zn toxicity to C. dubia in a series of natural waters with pH ranging between 7 and 8.3 with reasonable accuracy. The difference in the effect of pH on Zn toxicity between D. magna and C. dubia (2 phylogenetically closely related species) suggested by our results deserves further attention because of the importance of the cross-species application of bioavailability models in ecological risk-assessment procedures and environmental quality standard derivations for metals. Environ Toxicol Chem 2017;36:2750-2755. © 2017 SETAC.