Reproductive indices like gonad size, fecundity, egg size and sex steroid levels of estradiol-17β and testosterone, vitellogenin in the blood as well as bile conjugates and liver 7-ethoxyresorufin O-deethylase (EROD) activity were studied in populations of perch (Perca fluviatilis L.) and roach (Rutilus rutilus L.) and experimentally exposed juvenile whitefish (Coregonus lavaretus L. s.l.) at the Southern Lake Saimaa (S.E. Finland). Our studies showed that the introduction of elemental chlorine free (ECF) bleaching and secondary treatment of effluents in a modern activated sludge plant at the mill in 1992 have substantially reduced the exposure of feral and caged fish to organochlorines. The liver EROD activity was noticeably lower in feral and caged fish near the mill indicating lesser impacts on the liver mixed function oxygenase (MFO) system. However, at the mill site, liver EROD activies in feral and caged fish still tend to be one to four times higher than at the reference sites. Significantly decreased plasma estradiol-17β and testosterone concentrations in perch and roach in the period of development of the gonads (autumn and winter) indicate that there were endocrine disrupting compounds present in the lake receiving ECF pulp and paper mill effluents. Cause-effect relationships, however, are difficult to establish.
Sulfate toxicity to early life stages of European whitefish (Coregonus lavaretus) in soft freshwater
