Biological Assessment of Coral Reef Ecosystems and Their Degradation in the Gulf of Guinea, Delta State

This study assesses the biological condition and degradation status of coral reef formations in shallow coastal waters of Delta State, located in Nigeria's South South geopolitical zone and bordering the Gulf of Guinea. Coral reef systems along the Nigeria-Cameroon coast are poorly known internationally and have not been subject to standardised biological monitoring despite their unique biogeographic position and increasing pressure from oil spill pollution, coastal development, and sedimentation. Underwater visual census surveys were conducted by trained SCUBA divers at eight reef sites across two survey periods. Transects recorded coral cover by category, reef fish abundance and species composition, and macroinvertebrate diversity. Water quality including turbidity, salinity, temperature, and dissolved hydrocarbon levels was measured at each site. Mean live hard coral cover across all sites was 18.4 percent, significantly lower than the 30 percent threshold considered indicative of healthy reef condition. Sites closest to oil infrastructure had the lowest live coral cover (8.2%) and highest macroalgal dominance. Reef fish species richness averaged 22 species per transect, with fish biomass significantly lower at degraded sites. Evidence of bleaching was recorded at four sites. The study delivers a baseline condition assessment for Delta State coastal reefs and recommends establishment of a formal reef monitoring programme, inclusion of reef sites within Environmental Impact Assessment studies for offshore oil operations, and declaration of two sites with the highest coral cover as Marine Protected Areas. Keywords: coral reef, degradation, Gulf of Guinea, Delta State, reef fish.