Ecological risk assessment is commonly based on single-generation ecotoxicological tests that are usually performed at one standard temperature. We investigated the effects of nickel (Ni) on Daphnia magna reproduction at 15, 20, and 25 degrees C over 4 generations. Multigenerational Ni effects on D. magna reproduction depended on the magnitude of the effect in the first generation (F0) and showed very different patterns at different temperatures. At low effect level concentrations (<10% effect concentration [EC10] in F0), chronic Ni toxicity at 15 and 20 degrees C did not increase over 4 generations, and the increase in Ni toxicity at 25 degrees C observed in F1 and F2 in some Ni treatments did not persist into F3, where complete recovery of reproduction was observed. At higher effect level concentrations, the multigenerational Ni effects depended on the test temperature. In F0, Ni toxicity was 6.5-fold lower at 25 degrees C than at 15 degrees C (based on the median effect concentration), but the temperature effect on Ni toxicity was not explained by differences in Ni accumulation. At a lower temperature, lower internal Ni concentrations in D. magna were necessary to induce the same Ni toxicity as at a higher temperature. Overall, our results indicate that low single-generation chronic effect concentrations of Ni in D. magna (EC10 in the present study) are also protective in a long-term, multigenerational context and that temperature should be taken into account in the ecological risk assessment of Ni. |
