Ntangyong I. L. auteur aut IRD Chaigneau Alexis auteur aut IRD Morel Y. auteur aut IRD Assogba A. auteur aut IRD Okpeitchaa V. O. auteur aut IRD Duhaut T. auteur aut IRD Stieglitz Thomas auteur aut IRD Van Beek P. auteur aut IRD Baloitcha E. auteur aut IRD Sohou Z. auteur aut IRD Houssou V. M. C. auteur aut IRD Ouillon Sylvain auteur aut IRD text journalArticle eng text/pdf born digital access This study, based on five years of monthly in situ data collected from 2018 to 2022, examines the seasonal and interannual fluctuations of suspended particulate matter (SPM) concentration in Nokoue Lagoon, Benin. Seasonally, SPM exhibits significant variations primarily influenced by changes in river discharge. During lowflow periods (December to May), SPM concentrations are relatively low (<15 mg L-1) throughout the lagoon. During this time, slight temporal variations are correlated with wind energy and likely associated with wind-induced resuspension of sediments. This is confirmed by slightly higher concentrations of SPM in the bottom layers compared to the surface. Resuspension appears to be lower in the west than in the east, likely due to the increased presence of acadjas (brush parks) in the west, reducing fetch and wind intensity, thus decreasing resuspension. At the onset of the river flood period (July-August), associated with the West African monsoon, increased river flow generates a significant turbid plume extending from the northeast of the lagoon to the Cotonou channel, connecting the lagoon to the Atlantic Ocean. SPM levels then increase considerably (>100 mg L-1), with a pronounced SPM gradient from the western to eastern regions of the lagoon. The less dense freshwater laden with sediment from the rivers flows over the denser saline water of the lagoon, leading to slightly higher SPM concentrations in the surface layers. Between September and November, SPM concentration gradually decreases as river flows reach their peak values. Thus, on a seasonal scale, the relationships between SPM and river discharge show a temporal lag, resulting in a clockwise hysteresis cycle. This is explained by the early mobilization of fine sediments during rising river flows, followed by reduced sediment availability and dilution effects as the flood peaks. On an interannual scale, SPM variations are relatively low with slight temporal shifts observed in the formation and expansion of the turbid plume and peak SPM levels. The total SPM mass in the lagoon ranges from 0.2 to 0.3 x 10(4) tonnes during low-flow periods to 20-30 x 10(4) tonnes at the onset of flooding. We also discuss uncertainties associated with SPM determination, estimated at approximately 5-15%. This study leverages a unique database in West Africa and provides valuable insights into the hydro-sedimentary dynamics of Nokoue Lagoon. specialized Suspended particulate matter Seasonal and interannual variability Lagoon Nokoue Resuspension Sediments BENIN ATLANTIQUE 032 062 304 108821 [12 ] 2024 0272-7714 https://www.documentation.ird.fr/hor/fdi:010091023 10.1016/j.ecss.2024.108821 0272-7714 [F B010091023] https://www.documentation.ird.fr/hor/fdi:010091023 https://www.documentation.ird.fr/intranet/publi/2024-08/010091023.pdf Accès réservé (Intranet de l'IRD) IRD - Base Horizon / Pleins textes 2024-08-28 2026-06-12 fdi:010091023 fre