Influence Steeping of the Cassava Tubers on the Physico-Chemical Quality of Water and the Population of the Benthic Macroinvertebrates of River Pala in Central African Republic (CAR)

The aim of this study was to determine the influence of steeping of cassava tubers on the structure of Benthic Macroinvertebrates (BM) community in Central African Republic (CAR) in relation to the physicochemical quality of the water of Pala stream. The data were collected from May 2015 to April 2016 on a monthly frequency in 5 selected sampling stations of the upstream towards the downstream on the river. The physicochemical analyses were carried out using standard methods while the benthic macro fauna was collected using a net with a mesh size of 150 m on a total surface of approximately 6 m2 per station. The physicochemical analyses revealed a satisfactory water quality of the stations not located downstream from the point of steeping of the cassava tubers and a deterioration of the ecological quality in the stations located downstream from the point of steeping. A total of 2982 Benthic Macroinvertebrates, belonging to 79 taxa were identified and counted. Arthropods were the most diversified with 54 taxa and more abundant (53.11 %), followed by Molluscs (23 taxa, 37.79 % of abundance) and Annelids (2 taxa, 9.10 % of abundance). The station P5in the potamal area, which is the only station not directly located downstream from the steeping of the cassava tubers harbours the majority of Arthropods, dominated by Insects. In fact, the presence of oligotrophic characteristic crustaceans is confirming the auto purification capacity of the river due to a weak disturbance related to anthropic activities. In the rhythral and potamalstations downstream from the steeping of the cassava tubers, the strong abundance of Molluscs and the presence of Annelids, all polluotolerants, indicate the water quality degradation due to this practice of steeping.