The Forces Behind the Flux: Methane, Carbon Dioxide, and Nitrous Oxide Dynamics and Their Environmental Drivers in Restored Agricultural Wetlands

Abstract

Wetlands provide vital ecosystem services such as water filtration and flood mitigation but are also significant natural sources of greenhouse gases (GHGs), particularly methane (CH₄). This study examined seasonal and spatial patterns of CH₄, carbon dioxide (CO₂), and nitrous oxide (N₂O) emissions from seven restored agricultural wetlands in the Ontario portion of the Lake Erie Basin, focusing on diffusive and ebullitive flux pathways. Emissions were measured across four seasons, alongside water quality parameters used to identify key environmental drivers. Dissolved oxygen (DO) emerged as a strong driver of GHG fluxes, with lower DO concentrations consistently promoting higher CH₄, CO₂, and N₂O emissions. Duckweed cover also enhanced CH₄ production by creating anoxic conditions. GHG emissions peaked during summer months with heightened biological activity, while winter fluxes, though reduced, remained detectable, emphasizing the contribution of cold-season processes. N₂O emissions remained consistently low throughout the year. Across sites, methane emissions were generally low relative to natural temperate wetlands, except at one nutrient-enriched outlier (Site MA). Spatial variation within wetlands was minimal, suggesting that sampling from a single representative location may be sufficient for long-term monitoring. These findings show that restored agricultural wetlands can act as both carbon sinks and GHG sources depending on local biogeochemical conditions. By identifying major environmental controls on emissions, this study advances understanding of GHG dynamics in restored wetlands, informs efficient monitoring and modelling considerations, and strengthens national inventory and restoration policy development.