Investigation of Oil Spill Impacts on Mangrove Ecosystems in Bayelsa State

This study investigates the environmental impacts of crude oil spills on mangrove ecosystem health in Bayelsa State, South South Nigeria. The Niger Delta hosts one of the largest mangrove forests in the world, and chronic oil spill contamination from pipeline failures, equipment corrosion, and oil theft has severely degraded extensive areas of this critical ecosystem over decades of petroleum production. Field assessments were conducted in three oil-impacted mangrove sites and one reference site in the Nembe and Ogbia Local Government Areas. Parameters assessed include percentage canopy cover, tree mortality rates, benthic sediment total petroleum hydrocarbon concentrations, dissolved oxygen in tidal creek water, and benthic invertebrate community diversity using the Shannon-Weiner diversity index. Visual scoring of oiling severity was conducted across the study areas. Results show that oiled mangrove sites exhibit 45 to 78 percent reductions in canopy cover compared to the reference site, with Rhizophora racemosa and Avicennia africana showing the highest mortality. Sediment total petroleum hydrocarbon concentrations range from 2,800 to 18,500 milligrams per kilogram at heavily impacted sites, far exceeding intervention action levels. Benthic invertebrate diversity is severely reduced at all contaminated sites. Dissolved oxygen in affected tidal creeks is suppressed below 2 milligrams per litre, indicating anoxic conditions. The study concludes that ecological recovery requires both active remediation and protection from recontamination. Keywords: oil spill, mangrove ecosystem, Niger Delta, petroleum hydrocarbons, Bayelsa State.