BIOMARKER RESPONSES ALONG A POLLUTION GRADIENT - EFFECTS OF PULP AND PAPER-MILL EFFLUENTS ON CAGED WHITEFISH

Lake Saimaa (SE Finland) is a large oligotrophic lake receiving biolog ically treated effluent from a bleached kraft pulp and paper mill. Hat chery-reared juvenile whitefish (Coregonus lavaretus L. s.l.), a speci es known to feed on plankton and other particulates, were caged using a technique developed and optimized for this species and were exposed for one month in five downstream stations (3.3-16 km), Two reference s tations (4.5-8.5 km) upstream from the effluent outlet were used. An e xposure gradient of chlorinated organics was assessed by determining c oncentrations of conjugated chlorophenolics (CPs) in bile and CPs as w ell as extractable organic halogens (EOX) in gut lipids. Activities of liver cytochrome P4501A (CYP1A) monooxygenase and two conjugation enz ymes, uridinediphospho glucuronosyltransferase (UDP-GT) and glutathion e S-transferase (GST), were measured as indicators of exposure. Humora l antibody (IgM) level in plasma was used to estimate immune capacity. Other blood parameters were also analyzed. Fish caged nearest the mil l (3.3 km) had concentrations of CPs in bile 50-fold that of upstream reference fish, A gradual, distance-related, decrease of CPs in bile w as seen, A similar trend was seen in EOX and concentrations of CPs in gut lipid, Induction of CYP1A, measured as activity of 7-ethoxyresoruf in O-deethylase (EROD), was seen in fish at all downstream sites. At t he site nearest the mill, EROD activity was 13-fold higher compared to the reference area. No significant changes were seen in liver UDP-GT or GST. Levels of plasma IgM were 58-97% of reference values in fish c aged at downstream from the outfall. We conclude that biomarkers in th is study implicated the effluent as a causal factor and that relative severity of exposure was inversely related to distance from the efflue nt source.