Seasonal and interannual variability of salinity in a large West-African lagoon (Nokoué Lagoon, Benin)

Nokoué Lagoon in the South of Benin is a large intermittent coastal water body West Africa, which supports one largest inland fisheries region. The seasonal and interannual variability its salinity was studied, based on 3 years monthly surveys (Dec 2017–Dec 2020). This dataset allows us to identify fine-scale structures better understand salinization/desalinization processes at scales. During rainy season from May November, under influence freshwater inflows rivers northern shores, lagoon desalinizes zero October–November. dry December April, effect ocean tide, becomes progressively saltier, reaching typical salinities ∼25 April. On average, saltier southwestern part fresher towards river's mouths. Vertical stratification beginning main season. displays very marked variation with mean surface (bottom, respectively) 25 (25) April 2018 2020, respectively, against 16 (18) 2019. In absence river inflow data, box model shows that average sensitive small changes (or discharge), observed differences induced by variations 10–15 m3 s−1 during salinization phase, suggests ∼30% seawater entering flood-tides remains trapped enhances salinity. also indicates complete desalinization occurs for greater than ∼50–60 s−1. general mixing time scale 30–40 days.