Acute Toxicity of Water Accommodated Fractions (WAFs) of three Nigerian Crude Oils to Clarias gariepinus (Burchell, 1822)

Abstract

Abstract

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 objective of this study was to report LC values 50 obtained from acute toxicity tests on the African Catfish, C. gariepinus exposed to Water Accommodated Fraction (WAF) –heavy (Ebok), light (Meji) and medium (Erha) crude oils. Acute toxicity concentrations of 0%, 2%, 4%, 6% and 8%, 0%, 15%, 20%, 25% and 30% and 0%, 40%, 60%, 80% and 100% were used to determine the 96h Lethal Concentration (LC ) of 50 heavy, light and medium crude oils respectively. The analysis of variance (ANOVA) showed that there was a significant (p<0.05) difference in the quantal response of C. gariepinus to different concentrations of the various crude oil types at 24, 48, 72 and 96 hours exposure. These results showed that 96LC values for heavy, light and medium crude oils on C. 50 gariepinus were 0.028 mg TPH/l, 0.177 mg TPH/l and 0.742 mg TPH/l respectively. The 96LC of WAF showed that the heavy crude oil was six times more toxic than light and twenty 50 six times more toxic than medium and on toxicity categorization, the heavy, light and medium crude oils were very highly toxic, highly toxic and highly toxic on C. gariepinus. Based on the 0 acute toxicity tests, heavy with lower API (<22.3 C) gravity was more toxic than other crude oils on C. gariepinus. All crude oils are toxic to aquatic organisms especially the fish; their discharge into the water bodies during crude oil exploration, transportation, storage and even sabotage should be discouraged to protect the environment.