A comparison of the sensitivity of three Daphnia magna populations under chronic heavy metal stress.

The results from chromium, nickel, and zinc bioassays with three populations of Daphnia magna indicate that the investigated strains are differently sensitive. Sublethal concentrations which have a negative effect on survival and reproduction after 21 days of exposure also cause a significant reduction in the body length and brood size of primiparous females. Problems and consequences of the repeatability of such bioassays between laboratories in different countries are discussed.