Acute Toxicity of the Water-soluble Fraction of Nigerian Crude Oil on Fiddler Crabs (Uca tangeri)
George Awudum Edum
World Bank Africa Centre of Excellence for Oilfield Chemicals Research, University of Port Harcourt, PMB 5323, Choba, Port Harcourt, Nigeria.
Leo C. Osuji
World Bank Africa Centre of Excellence for Oilfield Chemicals Research, University of Port Harcourt, PMB 5323, Choba, Port Harcourt, Nigeria, Petroleum and Environmental Chemistry Research Group, Department of Pure and Industrial Chemistry, University of Port Harcourt, East-West Road, PMB 5323, Choba, Port Harcourt, Nigeria and Institute of Natural Resources, Environment and Sustainable Development (INRES), University of Port Harcourt, PMB 5323, Choba, Port Harcourt, Nigeria.
Hart A. Ibitoru
Institute of Natural Resources, Environment and Sustainable Development (INRES), University of Port Harcourt, PMB 5323, Choba, Port Harcourt, Nigeria and Department of Animal and Environmental Biology, University of Port Harcourt, P.M.B. 5323, Choba Rivers State, Nigeria.
Mudiaga C. Onojake *
World Bank Africa Centre of Excellence for Oilfield Chemicals Research, University of Port Harcourt, PMB 5323, Choba, Port Harcourt, Nigeria, Petroleum and Environmental Chemistry Research Group, Department of Pure and Industrial Chemistry, University of Port Harcourt, East-West Road, PMB 5323, Choba, Port Harcourt, Nigeria and Institute of Natural Resources, Environment and Sustainable Development (INRES), University of Port Harcourt, PMB 5323, Choba, Port Harcourt, Nigeria.
*Author to whom correspondence should be addressed.
Abstract
Six hundred and thirty (630) healthy samples of adult Uca tangeri were obtained from Chicoco mud in the oil- prone Buguma creek, Rivers State, Nigeria by handpicking and were transported to the laboratory in plastic containers where acclimation was done for 48hours prior to analysis. The crabs were divided into six groups in a randomized complete block design and monitored for 28 days. The test organisms were treated to different concentrations of the water-soluble fraction (WSF) of Bonny Light crude oil. The WSF caused marked exposure risk to the littoral organism, (U. tangeri), and was observed to have elicited a concentration-dependent mortality on the test organism. At 5 mg/L, mortality ranged from 10% to 20%, showing the initial effects of the toxicants on crab survival. At 10 mg/L, mortality increased to 20% to 30%, and at 15 mg/L, it rose sharply to 40% to 60%, reflecting a more severe impact. The highest concentration tested, 25 mg/L, resulted in 100% mortality, marking a lethal concentration threshold for U. tangeri. The toxicity of the WSF points to the base constituents of the test compound as seen in the altered physico-chemistry of the organism’s simulated habitat. In the event of any spill affecting the littoral ecosystem, expedient reclamation and contingencies are recommended to avoid acute lethality of such organisms. This would also prevent bioaccumulation of serious hazards in the human food chain.
Keywords: Water soluble fraction (WSF), bonny light, crude oil, mortality, lethal concentration