EVALUATION OF BIOMARKERS FOR EXPOSURE OF FISH TO EUCALYPT-BASED PULP-MILL EFFLUENT AND FOR DETERMINATION OF ROUTES OF EXPOSURE

Biomarkers have been used extensively to assess the impacts of pine-ba sed pulp mill effluent on fish species in the Northern Hemisphere; how ever, little research has been performed to evaluate the use of biomar kers to assess the effects of eucalypt-based pulp mill effluent. Conse quently, this series of experiments had two aims: to evaluate (1) the use of biomarkers for detecting exposure to eucalypt-based pulp mill e ffluent and (2) the use of biomarkers to determine the significance of the route of exposure. To determine the effects of eucalypt-based pul p mill effluent in the receiving water the contribution of dietary exp osure was measured, both alone and in conjunction with water column ex posure. Common jollytails (Galaxias maculatus) and Tasmanian blennies (Parablennius tasmanianus) were exposed to low levels (0.5-1%) 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 obta ined indicated that eucalypt-based pulp mill effluent had a minor effe ct on fish at concentrations that are found in the receiving water. Fi sh exposed by both routes showed minimal changes in liver structure an d ultrastructure, a three- to fourfold increase in ethoxyresorufin-O-d eethylase (EROD) activity, and no detectable induction of cytochrome P 4501A1. EROD induction, histopathology, and ultrastructure of the live r 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 eff luent. By exposing the fish to the effluent by only one route, the imp acts of the effluent may be underestimated in many instances. (C) 1998 by John Wiley & Sons, Inc.