Structure and Dynamics of Pelagic Microalgae in Response to Anthropogenic Pressures: The Banco River Case

This study was conducted to understand the structure and dynamics of microalgae in order to assess the ecological health of the Banco River. This river, located in the south of Côte d'Ivoire, is subject to considerable influence due to anthropogenic activities. To achieve this objective, microalgae as well as environmental parameters were sampled. Microalgae sampling took place at four points from July 2020 to June 2021, covering four climatic seasons, using a 20 µm mesh plankton net. Water samples of 250 ml at each station were taken for the extraction of chlorophyll pigments. However, high chlorophyll contents were obtained at station B1 (53 µg/l). In total, 158 microalgae taxa belonging to 53 genera, 32 families, 22 orders, 09 classes and 6 phyla were listed. The Euglenophytes (36.70%) represent the largest phylum with 58 taxa, followed by Chlorophytes (28.48%) with 45 taxa. The population of station B2 is more diverse, with 147 taxa, compared to the other stations. The evolution of the density shows that station B1 constitutes the environment with the highest density (4.77 × 10^6 cell/l). The organic pollution index (3.25–3.75) showed that the stations of the Banco River are moderately polluted.