Biogeography of Deep-Sea Benthic Communities in the Eastern Gulf of Guinea: A Nigerian Perspective

The deep-sea benthic communities of the eastern Gulf of Guinea represent one of the least explored marine biogeographic provinces on the Atlantic Ocean floor, yet they face growing disturbance pressure from deepwater hydrocarbon development in Nigerian offshore blocks. This dissertation provides the first systematic biogeographic characterisation of deep-sea benthic communities in the Nigerian exclusive economic zone at depths from 500 to 3,500 metres, investigating community structure, endemism patterns, connectivity with Atlantic deep-sea provinces, and vulnerability to disturbance. Macrofaunal and meiofaunal communities are sampled from 32 sites using box corers and epibenthic sledge deployments during three oceanographic cruises in 2022 to 2024. Organisms are identified to species level using morphological and molecular (COI and 16S barcoding) methods, with novel species descriptions submitted for taxonomic validation. Environmental drivers of community composition (depth, sediment grain size, organic carbon flux, oxygen concentration, bottom current velocity) are measured at each site. Multivariate ordination and gradient forest modelling identify the primary environmental gradients structuring community turnover across the study area. Connectivity with Atlantic deep-sea communities is assessed using population genetic analysis (microsatellite markers) for three numerically dominant taxa. A multi-criteria vulnerability assessment scores each major habitat type against sensitivity, resilience, and exposure metrics to produce a disturbance vulnerability map for Nigerian deep-sea areas relevant to oil and gas regulatory decisions. The dissertation establishes the empirical foundation for evidence-based deep-sea environmental management in Nigerian waters. Keywords: deep-sea benthic communities, biogeography, Gulf of Guinea, taxonomy, vulnerability assessment