Long-Term Ecological and Public Health Consequences of Oil Contamination in Mangrove Ecosystems in Cross River State, South South Nigeria

Mangrove ecosystems in Cross River State support critical ecological services and the livelihoods of thousands of coastal communities, yet the long-term consequences of cumulative oil contamination on both ecosystem function and community health outcomes remain inadequately characterized and theoretically underdeveloped. This dissertation integrates ecological health and planetary health frameworks to investigate the long-term consequences of oil contamination in mangrove ecosystems along a seventy-kilometre coastline in Cross River State. The research employed a longitudinal comparative design with three assessment time points over five years, combining satellite imagery analysis, ecosystem services quantification, sediment and water toxicology, benthic community assessments, and community health surveys administered to 1,200 residents across twelve fishing communities. Economic valuation of lost ecosystem services was conducted using benefit transfer and hedonic pricing methods. Results demonstrated progressive degradation of mangrove canopy cover in oil-contaminated zones at an annual rate of 3.4 percent, compared to 0.6 percent in control zones. Polycyclic aromatic hydrocarbon concentrations in sediment and fish tissues showed temporal increases despite the absence of new spill events, indicating remobilization from sediment reservoirs. Dietary fish consumption in contaminated communities was found to contribute to PAH intake levels associated with excess cancer risk. Community health data showed rising rates of dermatological conditions, gastrointestinal illness, and reported infertility over the study period. The dissertation makes original contributions to planetary health theory, ecosystem services valuation, and long-term community health impact assessment in oil-contaminated coastal environments. Keywords: oil contamination, mangrove ecosystems, public health, Cross River State, planetary health.