Physiological Disturbances in Fish Exposed to Bleached Kraft Mill Effluents

Physiological methods, previously used as health indicators in laboratory investigations on fish exposed to environmental pollutants, have been applied to feral fish inhabiting coastal waters polluted by bleached kraft mill effluents (BKME). The results show that BKME affect important physiological functions and thereby the state of health of the fish in the receiving body of water. Typical symptoms were reduced gonad growth, enlarged liver, strong induction of enzymes in the hepatic mixed function oxidase system, elevated content of ascorbic acid in liver tissue, altered carbohydrate metabolism, disturbed ion balance and marked effects on the red and white blood cell pattern. Good agreement was found between the toxic effects detected in fish exposed to BKME in nature and those observed in laboratory investigations. The toxic effects were most pronounced in fish living up to 4.5 km from the discharge source, but some disturbances could be observed even in fish caught 8-10 km from the kraft pulp plant. This indicates that the area of influence where the BKME exert biological effects is much larger than was previously considered.