Dissolved Organic Matter in the Arctic: What Does it Look Like, Why Does it Matter?
P.I.:
Claudia M. Boot
Proposal # 0852077
Claudia M. Boot has been awarded a Postdoctoral Fellowship in Polar Science to study dissolved organic matter in the Arctic. She will conduct her research under the mentorship of Dr. Josh Schimel (University of California Santa Barbara) and Dr. Matt Wallenstein (Colorado State University). Dr. Boot?s research will determine the major components of dissolved organic matter in the three vegetation types (tussock tundra, wet meadow, and shrub tundra), document seasonal variability of those components, and determine the molecular characteristics responsible for the variation. The results will improve models of carbon cycling in the Arctic. The fellowship will introduce Dr. Boot to Arctic research, and she will bring new chemical techniques to the laboratories of her mentors.
The aims of my National Science Foundation Office of Polar Programs postdoctoral fellowship were to learn how season and vegetation influence the composition of dissolved organic matter in an Arctic ecosystem, and to enhance my skills as an independent research scientist. Attached images illustrate the collection and processing of frozen Arctic soils. It is important to understand dissolved organic matter (DOM) dynamics because the solution state of this material mediates it biogeochemical cycling, either transferring elements such as carbon (C) from the soil back into the atmosphere (flux), or from the soil solution state to the solid state where it will typically be stored long-term. The balance of the transfer of C from soil to the atmosphere is sensitive to environmental variables such as temperature and moisture (seasonal influences) and also dependent upon different plant groups (vegetation). The overall chemical composition of DOM is one of the determining factors of storage versus flux, however the chemical make of DOM is exceedingly complex and the analytical tool necessary for probing its chemical characteristics have only just begun to emerge. Understanding DOM composition in the Arctic is particularly important because Arctic soils store huge amounts of C, and they are warming at a faster rate than the rest of the planet. The research supported by this funding has yielded results from two DOM chemical characterization methods, mass spectrometry (MS)-based metabolomics, and fluorescence excitation emission matrices (EEMs). This is the first application of metabolomics to Arctic ecosystem DOM and I found that the seasonal variables are stronger drivers of the chemical makeup of DOM than vegetation based ones, with a particularly large shift in the chemical makeup at the summer to winter transition (Figure 1). The data provided from the fluorescence EEMs data are somewhat contrary with vegetation type the major descriptor of the chemical composition from all seasonal collections. These data suggest that the metabolomics analysis may be a better descriptor of the microbially-derived, small molecular weight (less than 1000 amu) compounds characteristics of the DOM, while the fluorescence EEMs data may be a better indicator of large molecular weight (greater than 1000 amu) plant contribution to the DOM pool. The application of these descriptive tools has enhanced our knowledge of the complex DOM pool and how different components of it may be sensitive to different drivers. Through the funding provided by the OPP postdoctoral fellowship my analytical and collaborative skills have been sharpened leading to many additional collaborations with other junior and senior scientists alike. It is collaboration and transfer of knowledge at this nexus that advances our state of understanding and ability to ask (and answer) the most relevant questions to public interests today. The data collected and analyses supported by this fellowship will serve as the backbone for continued research on better understanding the drivers of DOM dynamics and how its chemical composition will feedback on patters of storage and flux for the global C balance.
