Does Geochemical Legacy Select for Soil Microbial Members in Establishing Wetland Functions?
EMSL Project ID
50823
Abstract
Wetland restoration efforts are critical to enhance carbon sequestration in biomass and reestablish ecosystem vitality and functions. The success of such restoration efforts are frequently assessed in terms of microbial processes like reduced decomposition of soil organic matter, and development of chemically reduced soil environment resulting in iron reduction and methane production (methanogenesis). As such, how these key microbial communities and their activities are reinstated as a result of flooding an upland soil is poorly understood and their temporal and spatial dynamics have not been systematically studied. The mechanistic understanding of how the complex dynamics of microbial community development, metabolic expression and activity co-occur or compete in their local redox environment can greatly impact our predictive understanding of these processes generally in submerged environments, and specifically, in ecosystems undergoing rapid changes in historic hydrologic conditions. Wetlands are among the largest natural contributors to the global emission of methane. Methane producing microorganisms or methanogens have a very limited substrate range and their in situ activities are often linked to intermediary ecosystem metabolism, i.e., a complex food web of interconnected microorganisms that catalyze essential intermediary processes that ultimately drive methanogenesis. For example, fermentation products like short-chain fatty acids and alcohols can be utilized by both iron reducers and methanogens. Thus, methane production may be competing for intermediary substrates formed as a result of microbial metabolism located higher up in the redox ladder, a concept rarely tested in natural soils. We approach this scarcely studied paradox in the context of microbial community stability (insensitivity to disturbance, i.e. altered redox state) and recovery (a community's return to a pre-disturbance condition) and test its relevance to wetland restoration goals.
The energetic favorability of processes associated with alternative terminal electron acceptors (nitrate, sulfate, iron) govern wetland carbon flux and methane biogeochemistry. This study will provide data to establish mechanistic links between microbial metabolism to trace gas fluxes to landscape-scale changes in physical (water-level, temperature) and geochemical (redox potential, pH, electron acceptor profiles) properties. Since, organic substrates or metabolites form the primary currency of exchange for microbial growth and activity, understanding how redox potential impacts the net accumulation/consumption of these compounds might be key to quantitatively link process rates. By taking advantage of the high-resolution quantification (1 micrometer limits of detection) of the NMR capabilities at EMSL, we hope to provide a proof-of-principle for how redox chemistry affects microbial processes in natural soils. Use of stable isotope guided-NMR will be particularly advantageous due to the non-destructive nature of sample preparation, analysis, and above all preservation of low-molecular weight and volatile metabolite groups that are fundamental to answering our research questions. Additionally, we aim to gain insights in to the community metabolome as the above-mentioned microbial communities develop. This will enable discovery of other microbial communities/processes that might serve as limiting factors for successful establishment of the above targeted communities/functions. We propose to use the Gas-Chromatography Mass Spectrometry for high-resolution analysis using an untargeted approach and build on its larger library of metabolites.
Project Details
Project type
Large-Scale EMSL Research
Start Date
2019-10-01
End Date
2021-12-31
Status
Closed
Released Data Link
Team
Principal Investigator
Co-Investigator(s)