Hydrocarbon-induced changes to metabolic and detoxification enzymes of the Australian crimson-spotted rainbowfish (Melanotaenia fluviatilis).

ABSTRACT

The toxicity of petroleum hydrocarbons to marine aquatic organisms has been widely investigated; however, the effects on freshwater environments have largely been ignored. Selected biomarkers were measured in a freshwater species, the crimson-spotted rainbowfish (Melanotaenia fluviatilis). Fish were exposed to either a water-accommodated fraction (WAF) of crude oil or a dispersed crude oil water-accommodated fraction (DCWAF) for 3 days and were depurated for 14 days. Generally, biomarkers were altered following the short-term exposures but recovered after 14 days of depuration. Metabolic enzymes measured in gill tissue were citrate synthase and lactate dehydrogenase (LDH). As a result of WAF and DCWAF exposures, citrate synthase and LDH activities increased. Enzyme activities returned to control levels following depuration. Subsequent to the WAF exposure, hepatic ethoxyresorufin-O-deethylase (EROD) activity levels were higher than controls and they returned to control levels during depuration. For the DCWAF exposure, EROD was induced by a TPH (total petroleum hydrocarbons) concentration of 14.5 mg/L; however, after depuration the 14.5 mg/L TPH group had lower EROD activity than did controls. There were no changes in liver- to body-weight ratios or the histopathological organization of gill or liver tissues. As the majority of biomarkers returned to control levels after 14 days of depuration, rainbowfish were able to recover from short-term exposures to crude oil and dispersed crude oil.