FOSL Summary: If exposed to a mixture of crude oil and Corexit 9500, an enzyme -- capable of biotransforming polycyclic hydrocarbons into carcinogenic or mutagenic compounds -- increases up to 1200% when in warmer water.
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The influence of water temperature on induced liver EROD activity in Atlantic cod (Gadus morhua) exposed to crude oil and oil dispersants, Ecotoxicology and Environmental Safety, January 15, 2011:
Juvenile Atlantic cod were exposed to either the water-accommodated fraction (WAF) or the chemically enhanced water-accommodated fraction (CEWAF) of Mediterranean South American (MESA), a medium grade crude oil at three different temperatures.
Two concentrations of each mixture were tested, 0.2% and 1.0% (v/v) at 2, 7 and 10 °C [Fahrenheit = 35.6, 44.6, and 50 degrees]
Corexit 9500 was the chemical dispersant tested.
The liver enzyme ethoxyresorufin-O-deethylase (EROD) was measured during a 72-h exposure.
The WAF of oil had significant (P<0.05) effect on enzyme activity compared to controls at only one sampling time: 48 h at 10 °C.
Exposure of CEWAF of oil resulted in significantly (P<0.05) elevated EROD activity compared to controls.
The level of EROD induction was temperature related with higher induction being observed in cod exposed to CEWAF at higher temperatures.
Total polycyclic aromatic hydrocarbon (PAH) concentrations in exposure water were significantly higher in chemically dispersed mixtures.
While PAH concentrations were lower in the 2 °C water compared to 7 or 10 °C (8.7 vs 11.9 μg mL−1), the level of EROD induction was approximately 9 and 12 times lower at 2 °C compared to 7 or 10 °C, respectively, suggesting the metabolic rate of the cod plays a role in the enzyme response.
These data suggest the risk of negative impacts associated with exposure to chemically dispersed oil may be affected by water temperature and that risk assessment of potential effects of WAF or CEWAF should consider the effects of water temperature on the physiology of the fish as well as the effectiveness of dispersants.
Definition of Ethoxyresorufin O-Deethylase [EROD], Sensagent Dictionary:
A liver microsomal cytochrome P-450 monooxygenase capable of biotransforming xenobiotics such as polycyclic hydrocarbons and halogenated aromatic hydrocarbons into carcinogenic or mutagenic compounds. They have been found in mammals and fish. This enzyme, encoded by CYP1A1 gene, can be measured by using ethoxyresorufin as a substrate for the ethoxyresorufin O-deethylase activity.