The ecological effects of oil spill on environmental media and organisms (pelagic, bottom dwelling organism) in the riverine areas of Odidi and Egwa in the Niger Delta ecological zone of Delta State was investigated approximately six months after the spill. The content of petroleum hydrocarbons and heavy metals (lead, copper, zinc, iron and chromium) in the water, sediment, fish (Clarias gariepinus) and snail (Pachymelania byronensis) was evaluated to determine the effect oil spill had on the environmental matrix and the organisms. The mean concentration of total petroleum hydrocarbon (TPH) in the sample matrix (water, sediment) and organisms (fish and snail) from Odidi and Egwa Rivers was above the Department of Petroleum Resources (DPR) limits of 50 mg/L and 5000 mg/kg. The control level of TPH in the media and organisms was less than 5 mg/kg. The mean water concentrations of iron and chromium were above their respective DPR limits of 1.00 and 0.03 mg/L. The concentrations recorded for iron in Odidi and Egwa waters was 2.96 ± 0.01 mg/L and 2.95 ± 0.08 mg/L while chromium was 0.33 ± 0.01 mg/L and 0.34 ± 0.01 mg/L respectively. Similarly, the mean concentrations of heavy metals in the water, sediment, cat fish (Clarias gariepinus) and snail (Pahymelania byronensis) were all significantly different from the control station (P<0.05). In other to prevent the adverse effects on environmental components and organisms resulting from oil spill, immediate clean-up of the environment and remediation measures should be carried out to prevent the bioaccumulative effects that could result from long term exposure to crude oil spill / pollution. This is with the view of safe guarding environmental media, aquatic fauna and subsequently man, who constantly feed on these organisms.

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