Post-Oil Spill Ecosystem Recovery Assessment in Gokana Local Government Area, Rivers State

Post-oil spill ecosystem recovery is a complex and protracted process, and rigorous scientific assessments are essential for verifying the effectiveness of remediation programmes and informing compensation frameworks. This study assessed the status of ecosystem recovery in five creek communities in Gokana Local Government Area, Rivers State, South South Nigeria, following documented oil spills that occurred between 2018 and 2021. Biological, chemical, and physical assessments were conducted at remediated and reference sites. Benthic invertebrate communities were sampled using a Van Veen grab, and fish assemblages were surveyed using multi-mesh gill nets. Sediment and water samples were analysed for total petroleum hydrocarbons, polycyclic aromatic hydrocarbons, and heavy metals. Mangrove regeneration was assessed through aerial photography analysis and seedling density counts in 5 by 5 metre quadrats. Total petroleum hydrocarbon concentrations in sediment exceeded NOSDRA remediation certification thresholds at three of five remediated sites, indicating incomplete recovery. Benthic invertebrate diversity remained significantly lower at remediated sites compared to reference sites, with pollution-tolerant taxa still dominating. Fish species richness was 35 percent lower at remediated creek sites compared to unimpacted reference creeks. No natural mangrove regeneration was recorded at two sites where soil contamination remained above 10,000 milligrams per kilogram dry weight. Only one of five sites met criteria for full ecological certification. The study highlights inadequacies in the current NOSDRA-certified remediation process and calls for internationally validated bioremediation standards and independent third-party verification. Keywords: oil spill recovery, remediation assessment, Gokana, Rivers State, ecosystem rehabilitation.