Comparative sensitivity of three populations of the cladoceran Moinodaphnia macleayi to acute and chronic uranium exposure

Assessment of differences in the response of three different populations of the tropical cladoceran Moinodaphnia macleayi to uranium exposure was eval uated. The populations tested included a laboratory stock (maintained for 1 0 years), a wild population collected from Bowerbird Billabong (an uncontam inated environment), and a population collected from Djalkmara Billabong (a relatively contaminated environment with elevated levels of uranium), loca ted on the Ranger uranium mine site, Jabiru East, NT, Australia. Chronic an d acute toxicity of uranium was determined for all three populations. The n o-observed-effect-concentration (NOEC; reproduction) and lowest observed-ef fect-concentration (LOEC; reproduction) for uranium ranged between 8-31 mug L-1 and 20-49 mug L-1, respectively, for all three populations. The 48 h E C50 (immobilization- lethality) for uranium ranged between 160-390 mug L-1 for all three populations. There was little difference in the response of t he three populations of M. macleayi to acute and chronic uranium exposure, although the response of the laboratory population to chronic uranium expos ure appeared more variable than the "wild" populations. There was no appare nt tolerance in the population of M. macleayi obtained from Djalkmara Billa bong when exposed to elevated levels of uranium. M. macleayi was significan tly more sensitive to uranium exposure than other species previously tested . It was concluded that the sensitivity of the laboratory population (to ur anium) is still representative of natural M. macleayi populations. (C) 2001 by John Wiley & Sons, Inc.