Ecological status of Chari-Logone River Complex using Benthic Macroinvertebrates and Physico-Chemical Variables

Abstract

This study aims to inventory benthic macroinvertebrates within the Chari-Logone River complex, two tributary rivers of Lake Chad for assessing the ecological status. The organisms were sampled monthly, from February to July 2023, at six stations following the multihabitat approach developed by stark using a kick net of 500 µm mesh porosity. Physico-chemical analyzes revealed water of average ecological quality with Temperature ​​ (22.6 - 30.12 °C), pH (5.48 - 8.10 UC), Conductivity (86 - 240 µS/cm), Oxygen (54 - 95.20 %), Turbidity (14 - 72 FTU), color (130 - 570 Pt-Co) or Orthophosphates ​​(0.1 - 3.7 mg/L). Thus, 28 taxa belonging to 2 phyla (Arthropods, Molluscs), 5 classes (Gastropods, Bivalves, Hexapods, Crustaceans and Arachnids), 12 orders and 21 families were identified. Most of these organisms are characteristic of polluted urban streams. Only the species Melanoides tuberculata, Melanoides nodicincta and Glabbiella tchadiensis were respectively omnipresent, regular and constant. All species identified as least recurrent in this study were polluo-tolerant organisms. The Chari-Logone River complex is disturbed, but ecological conditions seem to be restoring downstream from the city of N’Djamena with the appearance of Crustacea (Caridina africana), recognised as polluo-sensitive. The physico-chemical variables selected in this study are limited to have precise information on water quality since the organisms identified were pollutant-tolerant.