Subchronic metabolic effects and toxicity of a simulated pulp mill effluent on juvenile lake trout, Salmo trutta m. lacustris

Abstract

Juvenile lake trout ( Salmo trutta m. lacustris) were exposed for 7 weeks to 0.05× and 0.2 × 96-hr LC 50 concentrations of simulated bleached kraft pulp mill effluent (KME − Sa + CP). A sulfate soap preparation, composed mainly of resin and fatty acids, with added chlorophenols (CP, tri-, tetra-, and penta-CP) was used as the toxicant mixture. Concentrations of free CP in plasma and free and conjugated CP in bile were proportional to their concentrations in the water. The greatest total gradient between bile and water CP was 5.2 × 10 4 for pentachlorophenol. The activity of a liver polysubstrate monooxygenase (PSMO) system, assayed with three model substrates, increased 40 to 67% due to KME − Sa + CP. However, the increase was not directly dependent on the exposure concentration. In contrast to PSMO, activities of conjugating enzymes ( p-nitrophenol UDP-glucuronosyl and glutathione transferases) were decreased in the liver. Increased concentration of glutathione was noted in the liver and kidney. In addition, a small (9%) but significant decrease in blood hemoglobin concentration was observed at the higher exposure concentration. Although growth rate of lake trout was markedly decreased due to KME − Sa + CP, hydromineral balance and carbohydrate metabolism in fish were unaffected, indicating possible physiological compensation. On the other hand, lethality tests with lake trout preexposed to KME − Sa + CP at 0.2 × LC 50 revealed decreased tolerance, whereas at the lower exposure concentration it was unchanged. We therefore conclude that various physiological adjustments in trout during subchronic exposures were not adaptive in terms of short-term tolerance.