Entomofaunal diversity and involvement in the diagnosis of water quality in Afridougou's Drébot Lake used for drinking water supply in Gagnoa (Centre-West, Côte d'Ivoire)

The population of Gagnoa is growing, leading to the expansion of human activities such as agriculture, urbanisation and leisure activities around Drébot Lake, which is used to supply drinking water. These anthropogenic pressures are characterised by the discharge of toxic substances into this lake and the degradation of its ecological quality, which is still poorly understood. This study was carried out to provide the first data on the entomofauna and the ecological status of the water in Gagnoa's Drébot Lake. Sampling took place in February 2023 at 22 stations. Aquatic insects were collected using a turbid net (2.5 m2 of surface area sampled) and a Van Veen bucket (0.3 m2 of sediment per sample). Physico-chemical parameters were measured using a multiparameter. Spatial variations in physico-chemistry indicate that only transparency and depth varied significantly between sampling stations on Drébot Lake. The inventory revealed 317 insect individuals divided into 31 taxa, 19 families and 4 orders. The order Diptera (9 taxa) is the most diverse and the most abundant (141 individuals).Species richness is higher on the banks (28 taxa) than in open water (2 taxa).Predatory organisms dominate the trophic structure of the lake's insect population.The insect population was not very diversified, but balanced. Assessment of water quality using the Chironomidae index indicated that most of the sites surveyed have good quality water.