Relationships between Phytoplankton Structure and Environmental Variables in an African Tropical Reservoir

Relationships between phytoplankton communities and environmental factors were studied from samples collected from July 2020 to February 2021 in the Korhogo reservoir. Taxonomic composition, diversity and abundance of phytoplankton were studied at 5 stations in relation to physical and chemical factors. Based on the values for trophic states, Korhogo Reservoir was eutrophic. Phytoplankton taxonomic identification revealed 78 taxa, mainly, Euglenophyta (47.43% of taxa), Chlorophyta (29.49% of taxa). The highest densities were recorded during the dry season, then, the lowest densities during the rainy season and mainly at the end of the rainy season with some specific taxa like Microcystis aeruginosa, Merismopedia tenuissima and Trachelomonas volvocinopsis. Shannon diversity index values (H?) were generally high during the dry season, and low during the rainy season and particularly at the end of the rainy season, at all sampling sites. Regarding Evenness (E), the recorded values varied between 0.54 at station St2 at the end of the rainy season and 0.88 at station St5 during the dry season. No Significant differences (pgreater than0.05) in these indexes were recorded between seasons and sampling sites. The redundancy analysis (RDA) demonstrated a little relationship between environmental variables and abundant taxa, suggesting that other parameters were responsible for this high abundance.