Carbon Flux Dynamics in Freshwater Wetlands of the Hadejia-Nguru Wetland Complex, North East Nigeria

Freshwater wetlands are globally significant carbon sinks and sources, yet their carbon flux dynamics in semi-arid West African systems remain poorly characterised. This study measured carbon flux dynamics, including carbon dioxide and methane exchange, in three wetland vegetation types within the Hadejia-Nguru Wetland Complex of North East Nigeria over a hydrological year. Static chamber methods were used to measure soil carbon dioxide and methane fluxes at monthly intervals across emergent macrophyte, open water fringe, and seasonally flooded grassland habitats. Dissolved inorganic carbon in surface and pore waters was determined alongside water table depth, soil temperature, and organic carbon content as controlling variables. Seasonal variation in carbon flux was analysed in relation to inundation extent and vegetation phenology. Results showed strong seasonal patterns, with highest methane fluxes during peak inundation in the emergent macrophyte zones and lowest in seasonally flooded grasslands. Carbon dioxide uptake was greatest during the active growing season across all vegetation types. Annual net carbon balance varied by habitat, with emergent macrophyte zones functioning as net greenhouse gas sources when methane fluxes were expressed in carbon dioxide equivalents. Soil organic carbon content and water table depth were the strongest predictors of flux magnitude. The study provides baseline carbon flux data essential for including Hadejia-Nguru wetlands in Nigerian national greenhouse gas inventories and REDD-plus accounting frameworks. Keywords: carbon flux, freshwater wetlands, methane, Hadejia-Nguru, greenhouse gas.