Subacute physiological effects of bleached kraft mill effluent (BKME) on the liver of trout, Salmo gairdneri

Abstract

Rainbow trout ( Salmo gairdneri) were exposed for 10 and 30 days to microbiologically treated effluent of a bleached kraft pulp and paper mill (BKME). Throughout the experiments, the quality of dilution water, taken from an upstream location close to the mill, was allowed to vary both diurnally and seasonally (September–October) in a natural manner. The test concentrations averaged 0 (control), 0.6, 1.2, 2.0, and 5.1% (v/v) of BKME. Conjugates of all major resin acids and chlorinated phenolics of BKME, except chlorocatechols, were detected in trout bile. They comprised 93.1–99.9% of the total amounts in the bile. The level of conjugated resin acids increased linearly with the content of BKME in test water. On the other hand, no increase in concentration of conjugated phenolics was seen above 2.0% BKME. In the blood plasma no conjugates were analyzable. Concentrations of free resin acids in the blood plasma, but not in the bile, significantly increased at high test concentrations of BKME. No active excretion of free resin acids from plasma to bile can be inferred, but some of the phenolics—particularly 3,4,5,6-tetrachloroguaiacol—seem to be concentrated in the bile as a free compound. Changes in several biochemical parameters did not display any simple relationship with the external concentrations of BKME. In intermediate exposure concentrations, however, liver RNA and protein concentrations were decreased after 10 days but increased after 30 days. Condition of fish, relative size of the liver, and concentrations of liver glycogen and water were unresponsive to BKME at the dilutions investigated.