SURVEY OF RECEIVING-WATER ENVIRONMENTAL IMPACTS ASSOCIATED WITH DISCHARGES FROM PULP-MILLS .2. GONAD SIZE, LIVER SIZE, HEPATIC EROD ACTIVITY AND PLASMA SEX STEROID-LEVELS IN WHITE SUCKER

Fish collected from the receiving areas of 12 Canadian pulp mills were examined, including sites receiving effluent from kraft mills using c hlorine as well as sulfite mills. Field collections included sampling of receiving water for chemistry and toxicity testing, and sampling of local fish for organ weights, hepatic MFO (ethoxyresorufin-0-deethyla se, EROD) activity, plasma steroid levels, and levels of liver dioxins . The main objectives of this study were to determine whether the disc harge of effluent from pulp mills to sites other than Jackfish Bay was associated with physiological or biochemical disruptions in wild fish , whether there was any correlation between waste treatment and the pr esence of biological responses in wild fish, and whether there was any association between the use of chlorine as a bleaching agent and thes e responses. Although white sucker collected near bleached-kraft mills exhibited the highest EROD induction and dioxin levels, elevated enzy me activity was observed in fish from sites .that did not use chlorine , and depressions in plasma sex steroid levels was not correlated with the level of EROD activity. The absence of chlorine bleaching or the presence of secondary treatment did not eliminate responses in fish, i ncluding decreased circulating levels of sex steroids, decreased gonad al size, and increased liver size. This survey has shown that (a) indu ction of hepatic EROD enzymes and depressions of plasma sex steroid le vels during gonadal growth are found downstream of several pulp mills; (b) these changes are seen at some mills without chlorine bleaching a nd at mills that have secondary treatment; (c) substantial dilutions o f nontoxic effluent do not appear to remove these responses; (d) the d ominant factor determining the presence or absence of responses appear ed to be dilution level; and (e) lab toxicity tests on invertebrates, rainbow trout, and fat-head head minnows could not predict the presenc e of these responses in wild fish.