Seasonal variability of methane in the rivers and lagoons of Ivory Coast (West Africa)

(CH4) in three rivers (Comoé, Bia and Tanoé) and five lagoons (Grand-Lahou, Ebrié, Potou, Aby and Tendo) of Ivory Coast (West Africa), during the four main climatic seasons (high dry season, high rainy season, low dry season and low rainy season). The surface waters of the three rivers were over-saturated in CH4 with respect to atmospheric equilibrium (2221–38719%), and the seasonal variability of CH4 seemed to be largely controlled by dilution during the flooding period. The strong correlation of CH4 con-centrations with the partial pressure of CO2 (pCO2) and dissolved silicate (DSi) confirm the dominance of a continental sources (from soils) for both CO2 and CH4 in these rivers. Diffusive air–water CH4 fluxes ranged between 25 and 1187 lmol m-2 day-1, and annual integrated values were 288 ± 107, 155 ± 38, and 241 ± 91 lmol m-2 day-1 in the Comoé, Bia and Tanoe ́ rivers, respectively. In the five lagoons, surface waters were also over-saturated in CH4 (ranging from 1496 to 51843%). Diffusive air–water CH4 fluxes ranged between 20 and 2403 lmol m-2 day-1, and annual integrated values were 78 ± 34, 338 ± 217