Abstract:

This study assesses organic and nutrient pollution within the Urban Nature Reserve of the Grande Niaye of Pikine and Dependence (UNRGNPD), an urban wetland located in Dakar, Senegal. The findings reveal pronounced spatial heterogeneity: the Dependence exhibit elevated concentrations of ammonium and phosphates, reflecting the influence of domestic and agricultural discharges, whereas sulphates dominate in Technopole, associated with effluents from the wastewater treatment plant. Significant correlations between ammonium-phosphate and nitrate-sulphate concentrations confirm the multiple anthropogenic sources of pollution. The Organic Pollution Index (OPI) classifies all lakes as being subject to very high levels of pollution, with a mean Biological Oxygen Demand (BOD₅) of 23.36 mg/L, indicating a substantial risk of eutrophication. These pressures undermine fish biodiversity and threaten socio-economic activities such as fishing and market gardening. Seasonal and interannual variations further highlight the influence of climatic conditions on pollution dynamics. An integrated management approach combining discharge regulation, control of invasive species, and the implementation of nature-based solutions is essential to safeguard the ecosystem services of the UNRGNPD.