Trophic status of Yamoussoukro lakes and ecological impacts of anthropogenic activities

Abstract

Eutrophication, the natural aging process of an aquatic system, can be accelerated by enrichment of nutrient, particularly nitrogen and phosphorus, from anthropogenic discharges. This study aimed to determine the trophic status and assess the ecological impact of the Yamoussoukro lakes. To achieve this, first of all, the physicochemical pollution parameters were determined using the AFNOR, and HACH methods. Then, the trophic status of the lakes was assessed using the Organisation for Economic Co-operation and Development (OECD) grid. Finally, the phytoplankton biomass of these lakes was quantified as well as their coverage rates using the traveling inventory method. The results obtained reveal that the waters of these lakes were moderately oxygenated and loaded with biodegradable organic matter. Chlorophyll-a levels were high in almost all lakes (>10 μg/L). All the lakes waters studied in the town of Yamoussoukro could be classified as hypereutrophic. This eutrophication is manifested by an increased proliferation of invasive aquatic plants occupying more than half of the surface area of the lakes (from 50% to 100% coverage rate) with the main species being Nelumbo nucifera (Lotus).