EFFECT OF TEMPERATURE ON CHRONIC TOXICITY OF COPPER, ZINC, AND NICKEL TO DAPHNIA MAGNA

摘要

Few studies have considered the effect of temperature on the chronic sensitivity of Daphnia magna to other stressors. The present study investigated the effect of temperature on chronic metal toxicity and whether this effect differed among 4 different D. magna clones. Life table experiments were performed with copper, zinc, and nickel at 15 degrees C, 20 degrees C, and 25 degrees C. General linear modeling indicated that chronic Cu, Zn, and Ni toxicity to D. magna were all significantly affected by temperature. When averaged across clones, our results suggest that chronic metal toxicity to D. magna was higher at 15 degrees C than at 20 degrees C, which is the temperature used in standard toxicity tests. At 15 degrees C, the 21-d median effect concentrations (EC50s) of Cu, Zn, and Ni were 1.4 times, 1.1 times, and 1.3 times lower than at 20 degrees C, respectively. At 25 degrees C, chronic Cu and Zn toxicity did not change in comparison with 20 degrees C, but chronic Ni toxicity was lower (21-d EC50 of nickel at 25 degrees C was 1.6 times higher than at 20 degrees C). The same trends were observed for Cu and Ni when the 21-d 10% and 20% effect concentrations were considered as the effect estimator, but not for Zn, which warns against extrapolating temperature effects on chemical toxicity across effect sizes. Overall, however, chronic metal toxicity was generally highest at the lowest temperature investigated (15 degrees C), which is in contrast with the usually observed higher acute metal toxicity at higher temperatures. Furthermore, the effect of temperature on chronic Ni toxicity depended significantly on the clone. This warns against extrapolating results about effect of temperature on chemical toxicity from single clone studies to the population level. (C) 2016 SETAC