The effects of pulp and paper mill effluents on fish : a biomarker approach

Abstract

Physiological and biochemical biomarkers were studied in juvenile whitefish (Coregonus lavaretus L. s.l.) experimentally exposed to effluents from the pulp and paper industry. During 1991-1993, whitefish were caged in the recipient (Southern Lake Saimaa, Finland) of a bleached kraft pulp and paper mill. In 1992, the mill changed its processes and chlorine dioxide for the bleaching and activated sludge treatment was introduced. A comparative study (1993) showed considerably decreased effluent constituents in lake water. Thus, the bile accumulation of chlorophenolics (CPs) was only 0.5 %, and resin acids (RAs) 2 %, of that in 1991. Compared to the reference, whitefish liver 7-ethoxyresorufin O-deethylase (EROD) activity was 13-fold (1991) and 2-fold (1993) 3 km from the mill. The levels of plasma immunoglobulin M and blood hemoglobin were decreased in the exposed fish before, but not after, the mill renewals. Other parameters measured remained unchanged. The laboratory exposures (1992 and 1996) simulating real effluent concentrations confirmed the field observations well. In addition, 17ß-estradiol and testosterone were significantly decreased in fish exposed in the laboratory (1996). During 1995-1996 the area was extended to cover the whole of Southern Lake Saimaa, which has four pulp and paper mills. CPs and RAs accumulated at low levels in fish bile. EROD activity was 2- to 4-fold at sites 1-6 km from all the mills, whereas the cytochrome P450 1A1 (CYP1A1) gene was expressed only near one mill. The reproductive steroids, IgM, glucose or lactate were not changed, whereas vitellogenin gene was induced near one mill. However, the results indicate site specific inconsistency in the mixing and dispersion of effluents within the area, hindering the comparison of the mills. The selected biomarkers proved feasible and relevant in quantifying the effluent exposure and effects on fish, both in the laboratory and in the field. This study showed that the modernized mill processes and the advanced effluent treatment substantially reduced the load of harmful effluent constituents, diminishing biological impact on the receiving aquatic environments.