The impact of temperature on the acute toxicity of arsenate and arsenite to rainbow trout (Salmo gairdneri).

This research investigated the influence of temperature (5 or 15 degrees C) on the acute toxicity of waterborne arsenite and arsenate to rainbow trout. Trout exposed to arsenate at 5 degrees C had a 144-hr LC50 (95% fiducial limits) of 114.1 (106.7 to 121.9) mg liter-1, twice the value of 58 (50.6 to 66.4) mg liter-1 evident in fish exposed at 15 degrees C. Temperature had no effect on the toxicity of arsenite; 144-hr LC50's at 5 and 15 degrees C were 17.7 (16.5 to 18.9) and 20.7 (19.9 to 21.5) mg liter-1, respectively. When fish were exposed to 70 mg liter-1 arsenate for 72 hr, those held at 15 degrees C had mean whole-body arsenic levels that were five times higher than the levels in fish held at 5 degrees C. There were, however, essentially no differences in the patterns of arsenic uptake between 5 and 15 degrees C when the fish were exposed to arsenate at 0.7 or 1.2 of the 144-hr LC50 at each temperature, a strategy which compensates for (eliminates) temperature as a modifier of toxicity. Fish which were held in arsenate-free water after the 72-hr arsenate exposure depurated significantly more arsenic at 15 degrees C than at 5 degrees C. Despite this, it is apparent that enhanced uptake at 15 degrees C was the overriding factor controlling the differences in the expression of arsenate toxicity at the two temperatures.