Effects of ECF-bleached kraft mill effluent on reproductive steroids and liver MFO activity in populations of perch and roach

Samples of perch (Perca fluviatilis L.) and roach (Rutilus rutilus L.) populations were collected in Lake Saimaa in September-October, after the onset of vitellogenesis and deposition of yolk in the eggs. The study area received elemental chlorine-free (ECF)-bleached kraft mill effluent (BKME). The pulp and paper mill studied used chlorine dioxide for bleaching and its effluents were treated in a modern activated sludge plant. The amounts of chlorophenolics in the bile of perch and roach at the mill site, 1 km from the discharge point, were two to four times higher than in fish from the upstream reference site. In the roach population near the mill liver the 7-ethoxyresorufin O-deethylase (EROD) activity was four times that measured in the reference areas. However, the EROD activity in the perch remained unchanged. The liver 7-pentoxyresorufin O-dealkylase (PROD) activity was induced to twice the amount only in male roach near the mill, whereas the relative liver size (LSI) was increased in female and male roach and female perch. The plasma concentrations of oestradiol-17 beta were decreased in female perch and female roach, but increased in male roach at the mill site. Near the mill, vitellogenin gene expression was also reduced in female perch. In addition, the plasma testosterone concentrations were reduced in female and male perch near the mill. No differences were noted in the plasma immunoglobulin concentrations in roach and in the relative gonad size (GSI) in the perch and roach populations. The condition factor was significantly lower only in female roach near the mill.