The release of petroleum hydrocarbons into the environment from well blowouts, pipeline leaks, shipping accidents and tank washing poses an ongoing threat to marine ecosystems. Distinguishing the source of oil contamination in exposed biota can be relatively straightforward if samples of the oil are available but, in their absence, such discrimination in fish poses a major challenge. The use of biomarker analysis provides a useful tool to describe sub-lethal effects of toxicant exposure. In this study we describe the responses of 12 biomarkers in Lates calcarifer (Asian seabass) following chronic exposure to heavy fuel oil (HFO) and to Montara, a typical Australian medium crude oil (MCO).
Thirty-six juvenile fish were exposed to 1%w/w crude oil via diet for 33 days using a static renewal experimental design. A suite of biomarkers was measured: acetyl choline esterase (AChE), DNA damage (as serum 8-oxo-dG), heat shock protein (HSP70), ethoxyresorufin deethylase activity (EROD), biliary polycyclic aromatic hydrocarbon (PAH) metabolites, foraging ability, liver histological morphology, and physiological parameters (Fulton’s condition factor, hepatosomatic index and haematocrit).
Biliary PAH metabolites varied between test groups corresponding to the PAH profiles of the respective oils. EROD activity was significantly increased (p = 0.01) in fish exposed to HFO (2.08 pmol/min/mg.pr) compared to controls (0.96 pmol/min/mg.pr) but not MCO-exposed fish (0.99 pmol/min/mg.pr), reflecting the absence of EROD-inducing high molecular weight PAHs in MCO. Fish exposed to HFO displayed reduced foraging ability, possibly associated with the significantly decreased (p <0.05) AChE concentration in brain tissue in fish exposed to MCO (0.86ng/mg.pr) and HFO (0.69ng/mg.pr) compared to negative controls (0.90ng/mg.pr).
Using principal components analysis (PCA) it was possible to differentiate between fish exposed to HFO from those exposed to MCO. Inferences can be made about the composition of an oil based on the biomarker profiles in exposed fish.