Paleoecological Reconstruction of Sea Level Change and Ecosystem Shifts in the Niger Delta During the Holocene

Paleoecological records from the Niger Delta provide crucial context for interpreting present-day coastal change and projecting future ecosystem responses to sea level rise under climate change scenarios. This study reconstructed Holocene sea level change and associated ecosystem shifts in the western Niger Delta using sediment core analysis at two sites in Delta State. Sediment cores of up to 8 metres length were retrieved using a vibrocore system. Proxy-based paleoecological reconstructions were performed using pollen analysis, foraminifera assemblage analysis, ostracod assemblages, and stable carbon isotopes on organic matter fractions. Radiocarbon dating of discrete organic horizons was used to establish age-depth chronologies. Results revealed three distinct sedimentological units. The basal unit (approximately 9,000 to 6,000 years before present) contained freshwater pollen taxa and C3 plant stable carbon isotope signatures, indicating a prograding riverine delta. The middle unit (6,000 to 3,500 years before present) showed a marked transition to mangrove pollen dominance and increased foraminiferal abundance, consistent with marine transgression reaching its maximum extent. The upper unit (3,500 years before present to present) reflected renewed deltaic progradation with declining salinity indicators. Comparison of foraminiferal assemblages with modern analogues confirmed a sea level highstand approximately 0.8 metres above current levels at approximately 5,500 years before present. The reconstructed Holocene paleoecological trajectory provides natural analogue data for ecosystem and shoreline responses to projected sea level rise of 0.5 to 1.0 metres by 2100. Keywords: paleoecology, Holocene, Niger Delta, sea level reconstruction, foraminiferal analysis.