Original Investigation of the Long-Term Ecotoxicological Consequences of Chronic Vessel-Source Pollution in the Mangrove Ecosystems of the Niger Delta

Chronic vessel-source pollution from bilge water discharges, antifouling leachates, and fuel transfer losses imposes cumulative ecotoxicological stress on mangrove ecosystems that are among the most biologically productive and economically significant in West Africa. This study conducts an original investigation of the long-term ecotoxicological consequences of chronic vessel-source pollution in mangrove ecosystems of the central Niger Delta, integrating chemical analysis, ecotoxicology, and ecological assessment methods across a ten-year retrospective and two-year prospective study design. Study sites were selected using GIS-based vessel traffic intensity mapping to create a pollution exposure gradient from high-traffic vessel anchorage areas to remote reference sites. Sediment core analysis, pore water chemistry, bioaccumulation studies in sentinel organisms including mangrove periwinkles and mudskippers, and vegetation health assessments using remote sensing indices were combined in a multivariate analysis framework. The study documents a statistically significant gradient of ecotoxicological effects corresponding to vessel traffic intensity, including elevated tissue hydrocarbon concentrations in sentinel organisms at high-exposure sites, reduced pneumatophore density in mangrove stands adjacent to vessel anchorages, and altered sediment infaunal community composition. The original theoretical contribution is a cumulative ecotoxicological stress index calibrated specifically for Niger Delta mangrove conditions, providing a quantitative tool for environmental impact assessment of vessel operations. Keywords: ecotoxicology, vessel-source pollution, Niger Delta, mangrove ecosystem, cumulative stress index