Assessing the contribution of sediment bioirrigation to the oxidative removal of methane from a fluvial wetland.
EMSL Project ID
60056
Abstract
Wetlands are among the largest natural sources of the greenhouse gas methane. While the net fluxes of methane to the atmosphere are relatively well understood, the amount of methane-derived carbon that is retained in the wetlands is less well constrained. We provide preliminary geochemistry and isotope-based evidence that a substantial amount of methane at our study site is oxidized to carbon dioxide or transformed into biomass before it is emitted to the atmosphere. Methane is thereby prevented from entering the climate system. Moreover, our findings suggest that the sediment burrows of widespread tube-dwelling Chironomid larvae are hotspots of methane oxidation. The sediment bioirrigation by myriads of insect ecosystem engineers could thus be responsible for the oxidation of substantial amounts of methane, and represent an overlooked methane sink.With the support of the FICUS program and the participating facilities we plan to investigate the methane oxidation of the “sediment burrow microbiome” at high resolution using isotopic, geochemical, and microbial data. We will study methanotrophic populations and pathways inside the burrow and burrow walls. The microorganisms inside the burrows were shown to impact the nitrogen and phosphorous cycle in wetlands, but to our knowledge their methanotrophic capabilities and contribution to methane oxidation was not investigated in detail. Furthermore, although it was shown that bioirrigation enhances sediment respiration in fluvial wetlands, it remains unclear how this affects the oxidation and removal of methane from these ecosystems. We thus aim to assess the contribution of bioirrigation to methane oxidation in the burrows and investigate whether the methanotrophic activity by the burrow microbiome changes under different oxygen conditions. We will also characterize the volume, organic matter content, 3D-structure and oxygen dynamics in the burrow to better understand this widespread habitat. Finally, we will identify sources and pathways of methane production and quantify methane fluxes for the studied ecosystem. To accurately describe the methane sources, sinks and emission we will measure diffusive and ebullitive fluxes throughout the pond and study the microbiome and metabolisms that are responsible for the methane production.
Together the expected results will improve our understanding of the origins, cycling and emission of methane from a fluvial wetland ecosystem. Our work seeks to illuminate key hydro-biogeochemical processes through which methanotrophic microbes and ecosystem engineering insects influence the cycling of carbon and the removal of methane. The stimulation of methane oxidation through bioirrigation and the resulting transformation of methane into biomass of higher trophic levels represents a process that has not been studied sufficiently and is not included in detail in biogeochemical models. Due to the abundance of methanogenic freshwater sediments in wetlands worldwide, as well as the widespread occurrence of Chironomids in such wetlands, this bioirrigation-stimulated methane oxidation could greatly improve our understanding of methane fluxes to the atmosphere. The generated data will be useful for a broad scientific community, particularly in biogeochemistry, environmental (micro)biology, and ecosystems science. In addition, the data will be useful to improve Earth System models and informative for stakeholders and policy makers in their decisions on land use.
Project Details
Project type
FICUS Research
Start Date
2021-10-01
End Date
2023-11-15
Status
Closed
Released Data Link
Team
Principal Investigator
Co-Investigator(s)
Team Members