Long-term effects of cadmium in Lake Michigan water on average numbers and biomass in laboratory Daphnia population

Cadmium has long been recognized as a highly toxic element, but it was not until comparatively recently that concern has been expressed over the impact of anthropogenic emissions of cadmium into the environment. Very little is known about the long-term effects of cadmium on aquatic organisms, although zooplankton now appear to be more sensitive than either phytoplankton or fish and thus may be critical in determining the overall impact of cadmium on plankton-dominated ecosystems, such as the oceans or the Great Lakes. The long-term effect of elevated concentrations of cadmium in Lake Michigan water were studied on laboratory populations of Daphnia galeata mendotae, a species of some importance in all of the Great Lakes. Results indicated that an increase of 0.1 ppd in Lake Michigan would probably not have any readily detectable effect on the population of D. galeata mendotae, although there was no evidence for a true threshold for the effects of chronic Cd stress