Acclimation-Induced Change in Toxicity of Aluminum to Rainbow Trout (Salmo gairdneri)

When a group of rainbow trout (Salmo gairdneri) fingerlings was exposed to 87 μg Al/L for 1 and 2 wk, their threshold lethal concentration (LC50) increased to about 1.8 times the control LC50 of 175 μg Al/L. Raising sublethal exposure to 154 μg/L during the third week resulted in a similar ratio of 1.7 between LC50s of previously exposed and control fish. Thus, prior exposures of 0.5 and 0.9 of the control LC50 resulted in about the same increase in tolerance. The magnitude of the increase was similar to those reported in the literature for other metals. Such acclimation could assist in the survival of fish during spring and autumn surges of aluminum and other metals in surface waters acidified by atmospheric deposition of oxides of sulfur and nitrogen; those environmental changes in aluminum concentration parallel the concentrations used in this research. Experimental water simulated an acid lake with pH of 5.1–5.3 and total hardness of 11 mg/L.