Assessment of Sediment Quality in the Sangomar Marine Protected Area in Senegal Prior to Oil Development

Abstract

As Senegal embarks on the development of offshore oil resources, there is increasing concern regarding the potential environmental impacts on the adjacent sensitive coastal ecosystems. This study provides a critical baseline assessment of sediment contamination within the Sangomar Marine Protected Area (MPA), focusing specifically on the presence of heavy metals cadmium (Cd), lead (Pb), and mercury (Hg), and polycyclic aromatic hydrocarbons (PAHs), both known for their persistence and toxicity in marine environments. The investigation revealed that most contaminant concentrations remain below internationally recognized ecotoxicological thresholds, suggesting an overall low level of pollution in the area. However, a significant exception was identified at the Bakina station during the 2024 dry season, where cadmium concentrations reached a concerning hotspot value of 37.23 mg/kg, indicating localized pollution that may pose ecological risks. The PAHs contamination profile was dominated by 3- and 4-ring compounds such as fluoranthene, phenanthrene, and anthracene, consistent with pyrogenic sources likely stemming from atmospheric deposition of incomplete combustion products. While the Pollution Load Index (PLI) values generally indicate low to moderate contamination levels, the detection of localized contamination peaks highlights the vulnerability of the MPA, especially given the influence of seasonal hydrodynamics such as upwelling and the proximity of ongoing oil extraction activities. These findings underscore the urgent need for the establishment of comprehensive, long-term, and high-resolution environmental monitoring programs. Such initiatives will be essential to detect early signs of ecological degradation, support adaptive management, and safeguard the rich biodiversity and ecosystem services provided by this critical marine conservation area.