Peatlands Versus Permafrost: Landscape Features as Drivers of Dissolved Organic Matter Composition in West Siberian Rivers

Author:

Starr Sommer F.1ORCID,Frey Karen E.2ORCID,Smith Laurence C.3ORCID,Kellerman Anne M.1ORCID,McKenna Amy M.45ORCID,Spencer Robert G. M.1ORCID

Affiliation:

1. National High Magnetic Field Laboratory Geochemistry Group and Department of Earth, Ocean, and Atmospheric Science Florida State University Tallahassee FL USA

2. Graduate School of Geography Clark University Worcester MA USA

3. Department of Earth, Environmental, and Planetary Sciences Brown University Institute at Brown for Environment and Society Providence RI USA

4. National High Magnetic Field Laboratory FT‐ICR MS Group National High Magnetic Field Laboratory Tallahassee FL USA

5. Department of Soil and Crop Sciences Colorado State University Fort Collins CO USA

Abstract

AbstractWest Siberia contains some of the largest soil carbon stores on Earth owing to vast areas of peatlands and permafrost, with the region warming far faster than the global average. Organic matter transported in fluvial systems is likely to undergo distinct compositional changes as peatlands and permafrost warm. However, the influence of peatlands and permafrost on future dissolved organic matter (DOM) composition is not well characterized. To better understand how these environmental drivers may impact DOM composition in warming Arctic rivers, we used ultrahigh resolution Fourier‐transform ion cyclotron resonance mass spectrometry to analyze riverine DOM composition across a latitudinal gradient of West Siberia spanning both permafrost‐influenced and permafrost‐free watersheds and varying proportions of peatland cover. We find that peatland cover explains much of the variance in DOM composition in permafrost‐free watersheds in West Siberia, but this effect is suppressed in permafrost‐influenced watersheds. DOM from warm permafrost‐free watersheds was more heterogenous, higher molecular weight, and relatively nitrogen enriched in comparison to DOM from cold permafrost‐influenced watersheds, which were relatively enriched in energy‐rich peptide‐like and aliphatic compounds. Therefore, we predict that as these watersheds warm, West Siberian rivers will export more heterogeneous DOM with higher average molecular weight than at present. Such compositional shifts have been linked to different fates of DOM in downstream ecosystems. For example, a shift toward higher molecular weight, less energy‐rich DOM may lead to a change in the fate of this material, making it more susceptible to photochemical degradation processes, particularly in the receiving Arctic Ocean.

Funder

National Science Foundation

National Aeronautics and Space Administration

Division of Materials Research

National High Magnetic Field Laboratory

Division of Chemistry

Publisher

American Geophysical Union (AGU)

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