Spatio‐temporal distribution of phytoplankton in four coastal rivers of southeastern of Ivory Coast (Soumié, Eholié, Ehania and Noé)

Spatio‐temporal dynamics of phytoplankton and their relation to abiotic environmental factors in four rivers of south‐eastern Ivory Coast (Soumié, Eholié, Ehania and Noé) was analysed from July 2003 to March 2005. The pelagic zone of each river was sampled upstream and downstream. Phytoplankton abundance was higher in Noé River (154.3 10⁴ cells l⁻¹) and lower in Eholié river (23.05 10⁴ cells l⁻¹). Dominant taxa were Microcystis aeruginosa (Kütz.) Lemmerm. and Aphanocapsa incerta (Lemmerm.) Cronberg & Komárek. In general, minimum densities of phytoplankton were observed during the rainy season, while maximum were observed in dry season in the whole stations of the rivers studied, such periods corresponding to low and high concentrations of nitrates. Among the rivers surveyed, Eholié river seems to be the least disturbed because of its higher species diversity. Seasonality fluctuations of algae abundance appear to be influenced by the flow of water and nitrate levels. This work is a useful starting point for future research on micro algae in Ivory Coast.