EROD induction and biliary metabolite excretion following exposure to the water accommodated fraction of crude oil and to chemically dispersed crude oil

Immature Atlantic salmon (Salmo salar) were exposed to water accommodated fraction (WAF) of Bass Strait crude oil or to Corexit 9527-dispersed crude oil for 6 days, followed by a depuration period of 29 days. Serum sorbitol dehydrogenase (SDH) levels, indicator of liver damages, remained low during the experiment. Hepatic EROD activity was induced within 2 days following the onset of the exposure in both treatments, and persisted for 2-4 and 4-6 days after transfer to clean sea water in the WAF and dispersed oil treatment, respectively. Naphthalene-type metabolites, determined by fixed-wavelength fluorescence detection, appeared in the bile of the fish with 2 days' delay compared to EROD induction. In both treatments, EROD activity induction and levels of naphthalene-type metabolites in the bile were significantly related. The biliary levels of naphthalene-type metabolites were over 15 times higher in fish exposed to dispersed crude oil relative to fish exposed to the WAF of Bass Strait crude oil. BaP-type metabolites appeared only in the bile of the fish exposed to the WAF, possibly due to BaP-type compounds remaining associated with the dispersant in the water column or to an inhibition of Phase II detoxification enzymes by the dispersant. Bile metabolites as determined by fixed-wavelength fluorescence and EROD induction appear to be sensitive and complementary biomarkers of exposure to PAH.