Diversity And Spatial Distribution of Benthic Macroinvertebrates of The Sota River in Benin

Abstract

The management of running fresh waters requires a good knowledge of their state, their physico-chemical state and biological transformation. Benthic macroinvertebrates are recognized as a biological tool of choice for highlighting disturbances that affect aquatic ecosystems. This study aims to highlight the spatial distribution of macroinvertebrates bio-indicators of the water quality of the Sota river in northern Bénin. The collection of samples was carried out in April during the recession according to the sampling protocol of the Normalized Global Biological Index (IBGN). Thus, a Surber with a unit area of ​​1/20 m2 and a mesh size of 100 μm was used to harvest macroinvertebrates at four stations: Nassikonsi, Karani, Gbéssé and Koki. Twelve samples were taken per station. These are four samplings of macroinvertebrates in the dominant habitats, four samples taken from marginal habitats and four from complementary habitats. Before sampling, the physico-chemical parameters including temperature, pH, conductivity, transparency, depth and Total Dissolved Solid (TDS) were measured per station. The study identified 10,377 individuals of macroinvertebrates divided into 25 families and 11 orders. This community is made up of 98.17% Insects, 0.83% Shellfish, 0.44% Molluscs, 0.53% Worms and 0.03% Hydracarians. The Diptera order is the most important and constitutes 91.9% of the total richness of macroinvertebrates collected. The chironomidae (78.6%) and ceratopogonidae (13.1%) families are the most frequent and the most abundant. The low values ​​of the Shannon diversity and Piélou equitability indices recorded at the Gbesse and Karani stations reveal that the macroinvertebrate community of these stations is unbalanced and not very diversified. This situation could well be the result of the deterioration of the water quality of the Sota river.