ABSTRACT
The adverse effect of crude oil on aquatic ecosystem is a modern day peril. This study investigated the acute toxicities of some Nigerian crude oil (Forcados, Bonnylight and Qua-Iboe) against Clarias gariepinus and the antioxidant enzyme response of the fish to the pollutants. The toxicity assessment was based on LC50 at 96 h. Static renewal bioassays were used to determine the toxicological effects of the 3 crude oils on the antioxidant enzymes of post juveniles Clarias gariepinus using the liver. The 96 h LC50 value for Qua Iboe was 18.966 mL L(-1), Forcados, 2.776 mL L(-1) and Bonny light, 3.948 mL L(-1), indicating that Forcados is the most toxic of the crude oils. Induction of the Glutathione-S-transferase (GST), Glutathione (GSH), Superoxide dismutase (SOD) and Catalase (CAT) in the liver of Clarias gariepinus exposed to Forcados and Bonny light for a period of 28 days was inhibited while it was enhanced in Qua-Iboe crude oil. Malondialdehyde (MDA) levels increased with increasing toxicity and exposure time. SOD, CAT, GSH, GST and MDA are reliable environmental biomarkers for crude oil induced oxidative stress in Clarias gariepinus and therefore useful biological indicators of environmental contamination in the aquatic ecosystem.
