Wetlands play an important role in the global carbon cycle, yet their contribution to greenhouse gas emissions depends strongly on subsurface redox conditions and hydrological setting. Mediterranean wetlands are characterized by pronounced spatial heterogeneity and seasonal variability, complicating the interpretation of carbon cycling processes.
This study focuses on biogeochemical processes in the sediments across several inland wetland sites in Israel. Among the sites studied, the Ein Afek Nature Reserve included an assessment of spatial and temporal dynamics. Sediment cores and porewater profiles were collected at four sampling locations representing varying hydrological and ecological settings, including spring, open-water areas, and vegetated margins. Geochemical characteristic included measurements of dissolved inorganic carbon (DIC), sulfate, iron, manganese, and methane (CH₄).
Results from Ein Afek indicate that redox processes are active throughout the wetland but vary markedly between habitats and seasons. Open-water locations are generally dominated by iron and manganese reduction. In contrast, littoral sediments that contains elevated organic-matter consistently exhibit more advanced redox conditions and clear methane production, regardless of seasonality.
Sulfate decrease with depth was observed across all the profiles indicative of active redox process throughout the site. Surprisingly, in several sediment profiles, sulfate concentrations show an increase at depth. Moreover, at some locations this trend persists across seasons. This pattern cannot be explained only by in situ microbial consumption and suggests that advective and/or diffusion transport of sulfate from deeper source or lateral flow paths contributes to porewater chemistry in parts of the wetland.
These findings highlight the need to consider hydrological transport alongside sedimentary redox processes when evaluating carbon sequestration potential and greenhouse gas production in wetland systems.