GENETIC TOXICITY OF PULP-MILL EFFLUENT ON JUVENILE CHINOOK SALMON (ONCORHYNCHUS-TSHAWYTSCHA) USING FLOW-CYTOMETRY

On-site bioassays were conducted at the furthest upstream pulp mill on the Fraser River in British Columbia Uncontaminated river water was u sed to dilute treated effluent as discharged from the final diffuser p ond. A single cohort of juvenile (8-10gm) chinook salmon (Oncorhynchus tshawTtscha) was divided into an hypoxic group receiving 65% oxygen s aturated water and a normoxic group receiving ambient 88% oxygen satur ated water. Both groups were exposed over a period of 30 days to efflu ent concentrations of 2%, 4%, 8%, and 16%, while the controls received uncontaminated river water. This range of concentrations spanned thos e encountered by wild juvenile salmon overwintering in the upper Frase r River mainstem. The blood when analyzed by flow cytometry showed sig nificant concentration-dependent clastogenic damage in both the normox ic and hypoxic groups starting at the 4% concentration. A concentratio n-response curve was determined from the hypoxic data set. Genetic imp lications of mutagenic damage to natural populations of chinook salmon are discussed along with the utility of the flow cytometer in detecti ng genotoxic damage. (C) 1997 IAWQ.