Inorganic Monomeric Aluminum and pH as Predictors of Acidic Water Toxicity to Brook Trout (Salvelinus fontinalis)

Inorganic monomeric aluminum concentrations were found to be the primary determinant of survival of brook trout feeding fry exposed for 21 d to various combinations of total aluminum and pH, plus several concentrations of fluoride or DOC, or several temperatures. Total aluminum concentrations in the 4 × 4 × 4 experimental matrices ranged from 3–1276 ppb, pH from 4.4–6.7, fluoride from <10–328 ppb, DOC from <1–9.2 ppm, and temperatures from 5.4–12.0 °C. Stepwise logistic regression was used to determine the significance of the effect of each water quality variable on survival. Inorganic monomeric aluminum accounted for 78–98% of the variation in survival. Except in the fluoride bioassay where pH was not significant, pH was the second-most important variable, accounting for up to 16% of the variation in survival. Fluoride or temperature accounted for 1–2% of the variation in survival, while DOC accounted for 6% of the variation in survival.