Biomarkers have been used extensively to assess the impacts of pine-based pulp mill effluent on fish species in the Northern Hemisphere; however, little research has been performed to evaluate the use of biomarkers to assess the effects of eucalypt-based pulp mill effluent. Consequently, ( ) this series of experiments had two aims: to evaluate 1 the use of biomarkers for detecting exposure to ( ) eucalypt-based pulp mill effluent and 2 the use of biomarkers to determine the significance of the route of exposure. To determine the effects of eucalypt-based pulp mill effluent in the receiving water the contribution of dietary exposure was measured, both alone and in conjunction with water column ( ) ( ) exposure. Common jollytails Galaxias maculatus and Tasmanian blennies Parablennius tasmanianus ( ) were exposed to low levels 0.5α1% of pulp mill effluent via the food chain, or via the water column or combined food chain and water column. Selected biomarkers were used to detect any sublethal effects caused by exposure to the effluent.
Results obtained indicated that eucalypt-based pulp mill effluent had a minor effect on fish at concentrations that are found in the receiving water. Fish exposed by both routes showed minimal changes in liver structure and ultrastructure, a three-to fourfold increase in ethoxyresorufin-O-deethyl-( ) ase EROD activity, and no detectable induction of cytochrome P4501A1. EROD induction, histopathology, and ultrastructure of the liver were proven to be useful biomarkers for the detection of exposure to low levels of eucalypt-based pulp mill effluent. Further, the results obtained from that series of bioassays have implications in relation to the methodologies used for assessing the effects of any complex effluent. By exposing the fish to the effluent by only one route, the impacts of the effluent may be underestimated in many instances.