Multi-parameter oceanographic survey on the Continental Shelf of Bénin during the Warm Season

Abstract

The objective of the study was to characterize the oceanographic parameters of the Continental Shelf of Bénin. The survey carried out during the warm season (February 2024) has provided insight into various oceanographic parameters such as temperature, salinity, oxygen, and water masses, which were essential for primary production, the first step in marine biological productivity. Using an oceanographic campaign integrating high-resolution CTD (Conductivity Temperature Depth) measurements, the results indicated surface temperatures range from 29 to 30 °C, dropping rapidly to 19-24 °C at a depth of 35 m. The stratification of the water column, influenced by winds and seasonal variations, affected vertical mixing and temperature distribution. Surface salinity fluctuated between 33.5 PSU and 34.4 PSU, increasing to 36 PSU with depth. Oxygen concentrations peaked between 10 and 30 meters before gradually decreasing beyond 40 m. The distribution of fluorescence showed variable concentrations across different regions and depths. Finally, the TS diagram identified the surface layer (Tropical Surface Water - TSW), the Subtropical Underwater (STUW) at 40 m and the South Atlantic Central Water (SACW) below 100 m, three distinct water masses, characterized by temperatures below 19 °C and decreasing salinity. These data collected for the warm season on the continental shelf of Bénin, highlight the crucial role of stratification driving the dynamics pelagic ecosystems. They provide a valuable foundation for modelling the impacts of climate change on fishery resources in the Gulf of Bénin.