Impact of Leachates on the Structure of the Phytoplankton Population and the Water Quality in the Peri-Urban Stream Ntinetchoueh in a Mountainous Region (Bafoussam, West Cameroon)

Abstract

Landfill leachates represent a major threat to freshwater ecosystems, particularly in rapidly urbanizing regions of Sub-Saharan Africa. This study investigated the effects of leachates from the Banefo landfill (HYSACAM) on the physicochemical characteristics and phytoplankton community structure of the Ntinetchoueh stream (Bafoussam, West Cameroon) over a seasonal cycle (April 2023 to February 2024). Five sampling stations were monitored, including sites exposed to leachate discharge. Water quality analysis revealed a relatively low temperature (21.3?C ± 0.24?C), a slightly alkaline conditions (pH 7.8 ± 0.14), and a moderate mineralization (339.42 ± 54.6 μS/cm), coupled with elevated CO 2 (14.55 ± 6.35 mg/L) and nutrient concentrations, notably NH 4 + (0.8 ± 0.32 mg/L) and orthophosphates (0.88 ± 0.22 mg/L), indicating substantial organic pollution. At the impacted station (S3), leachate inputs significantly increased conductivity and nitrogenous compounds while reducing Dissolved Oxygen (O 2 ) and pH. A total of 57 phytoplankton species were identified across four major classes, with Bacillariophyceae dominating community structure (79% of total density). Synedra ulna was the most abundant species, while Oscillatoria sp. and Navicula cryptocephala were the only regular species, whereas Bacillariaceae exhibited the highest taxonomic diversity. Species richness peaked upstream of contamination (S2), while maximum cell densities were recorded during the dry season. The predominance of accessory taxa (70.17%) reflects high ecological sensitivity to environmental stress. Overall, leachate inputs drive nutrient enrichment and physicochemical alterations, leading to significant shifts in phytoplankton structure and a decline in aquatic biodiversity.