Acute Toxicity of the Water-soluble Fraction of Nigerian Crude Oil on Fiddler Crabs (Uca tangeri)

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.