Comparative study of acute toxicity of three Nigerian crude oils using oil in water dispersion (OWD) method on Clarias gariepinus (African catfish)
Oil industry activities such as exploration, transportation, storage, use and disposal, as well as oil spills are sources of major contamination problems in Niger Delta, which have significant deleterious effects on aquatic organisms. The study was to investigate LC50 values obtained from acute toxicity tests on C.gariepinus using Oil in Water Dispersion (OWD) of Ebok,Meji and Erha. The acute toxicity concentrations of Ebok(0, 4, 6, 8 and 10ml/l), Meji (0, 15, 20, 25, and 30 ml/l) andErha (37.5, 50, 62.5 and 75ml/l)were used to determine the 96h Lethal Concentration (LC50) respectively. The analysis of variance (ANOVA) showed that there was a significant difference (p<0.05) in the quantal response of C.gariepinus to different concentrations of Ebok, Meji and Erha crude oils at 24, 48, 72 and 96hours of exposure. These results showed that 96LC50 values for Ebok, Meji and Erha crude oils on C.gariepinus were 6.35 ml/l, 18.35 ml/l and 32.04ml respectively. These showed that Ebok was three times more toxic than Meji and five times more toxic than Erha while Meji crude oil was two times more toxic than Erha on C.gariepinus. Based on the acute toxicity tests, Ebok with lower API gravity is more toxic than other crude oils in C.gariepinus. All crude oils are toxic to aquatic organisms especially the fish; their discharge into the water bodies during crude oil exploration, transportation and storage should be discouraged for a safety environment.