Reproduction Sensitivity of Five Daphnia Species to Nickel

In Japan, data on the reproduction sensitivity of Daphnia magna , which is a widely used organism in laboratory toxicity tests, to nickel are key to determination of water quality target values for nickel, which are used to set values for the environmental quality standards for conservation of the living environment. However, the use of data on the sensitivity of more than one species, including native species, will provide more relevant values. In this study, sensitivity of reproduction to nickel was investigated for five Daphnia species, D. magna , D. similis , D. pulex , D. galeata and D. ambigua , four of which are native to Japan. The no observed effect concentration and the 10% effect concen tration (EC 10 ) values of dissolved nickel for reproduction were below the lowest test concentration and 7.9 µg/L for D. magna , 4.6 and 11.2 µg/L for D. similis , 26 and 25.8 µg/L for D. pulex , 23 and 41.0 µg/L for D. galeata , and 62 and 63.8 µg/L for D. ambigua , respectively. Our results indicate that use of ecotoxicity data for native, ecologically relevant Daphnia species can strongly influence the determination of the water quality target values for nickel.