Assessment of the Overall Ecotoxicity Associated with the Bioavailable Fraction of Trace Metals in Surface Sediments Along the Senegalese Coast on Aliivibrio fischeri

Bioavailable trace metals in sediments can be a significant source of contamination for aquatic organisms. The present study aims to evaluate the overall toxicity of the bioavailable fraction of Pb and Cd in sediments from the Senegalese coast on the bacterium Aliivibrio fischeri. Surface sediment samples were collected at five sites (Rufisque, Soumbedioune, Saint-Louis, Hann, and Kayar) on the Senegalese coast during the dry and wet seasons, and trace metals content were determined by flame atomic absorption spectrophotometry. The results revealed a high level of contamination at the Rufisque and Soumbedioune sites, mainly related to lead and more pronounced during the dry season. In contrast, cadmium had the highest bioavailable fraction, exceeding 80% during the dry season at the Soumbedioune, Rufisque, and Saint-Louis sites, suggesting an anthropogenic origin for these metals. The results of the test carried out on the marine bacterium Aliivibrio fischeri confirm this observation by highlighting a proven higher toxicity of sediments during the dry season at the Soumbedioune site, followed by Rufisque, compared to the Kayar control site. Ultimately, this work has shown that even though lead contributes more to sediment contamination, the harmful effects on aquatic life are more related to cadmium due to its higher bioavailability. These effects are more pronounced in the dry season and at Soumbedioune due to the discharge of domestic and industrial wastewater without prior treatment.