| Field and laboratory experiments examined the effects of heavy metal exposure on metallothionein (MT), Cu, Zn, and Cd concentrations in liver and kidney of freshwater fish. In 1986, populations of white sucker (Catostomus commersoni) and northern pike (Esox lucius) were sampled from eight lakes near the Cu/Zn smelter at Flin Flon, Manitoba, Canada. Cu and Zn concentrations in pike and sucker liver were lower than in previous studies in 1976 and 1982. These reductions in liver metal concentrations (and the absence of hepatic MT induction in both species) corresponded to lower metal concentrations in recent sediments, and appeared to reflect reductions in heavy metal deposition near the smelter since a 251 m stack began operation in 1974. In contrast to liver, Cu and Zn concentrations in kidney were elevated relative to fish from reference lakes. It is currently not known whether renal metal concentrations are decreasing over time in the fish populations near Flin Flon.; Cd concentrations in northern pike liver and kidney were statistically related to sediment Cd concentrations, but Cd was not bioaccumulating in fish from any lakes near the smelter. A laboratory experiment indicated that Cd bioaccumulation in rainbow trout (Oncoryhnchus mykiss) liver was a function of the ratio of Cu and Zn to Cd in the diet. In future, the potential for Cd-metal interactions to minimize Cd toxicity in the environment should not be overlooked. |
