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Biogeosciences An interactive open-access journal of the European Geosciences Union
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Volume 13, issue 17 | Copyright

Special issue: Climate–carbon–cryosphere interactions in the...

Biogeosciences, 13, 4899-4914, 2016
https://doi.org/10.5194/bg-13-4899-2016
© Author(s) 2016. This work is distributed under
the Creative Commons Attribution 3.0 License.

Research article 06 Sep 2016

Research article | 06 Sep 2016

Source, transport and fate of soil organic matter inferred from microbial biomarker lipids on the East Siberian Arctic Shelf

Juliane Bischoff1,a, Robert B. Sparkes2,b, Ayça Doğrul Selver2,3, Robert G. M. Spencer4, Örjan Gustafsson5, Igor P. Semiletov6,7,8, Oleg V. Dudarev7,8, Dirk Wagner9, Elizaveta Rivkina10, Bart E. van Dongen2, and Helen M. Talbot1 Juliane Bischoff et al.
  • 1School of Civil Engineering and Geosciences, Newcastle University, Newcastle upon Tyne, UK
  • 2School of Earth and Environmental Sciences and Williamson Research Centre for Molecular Environmental Science, University of Manchester, Manchester, UK
  • 3Balıkesir University, Geological Engineering Department, Balıkesir, Turkey
  • 4Earth, Ocean and Atmospheric Science, Florida State University, Tallahassee, FL, USA
  • 5Department of Environmental Science and Analytical Chemistry (ACES) and the Bolin Centre for Climate Research, Stockholm University, Stockholm, Sweden
  • 6Pacific Oceanological Institute, Far Eastern Branch of the Russian Academy of Sciences, Vladivostok, Russia
  • 7International Arctic Research Center, University of Alaska, Fairbanks, USA
  • 8National Tomsk Research Polytechnic University, Tomsk, Russia
  • 9GFZ German Research Centre for Geosciences, Helmholtz Centre Potsdam, Section 5.3 Geomicrobiology, Telegrafenberg, Potsdam, Germany
  • 10Institute of Physicochemical and Biological Problems in Soil Science, Russian Academy of Sciences, Pushchino, Russia
  • anow at: The Lyell Centre, Heriot-Watt University, Edinburgh, UK
  • bnow at: School of Science and the Environment, Manchester Metropolitan University, Manchester, UK

Abstract. The Siberian Arctic contains a globally significant pool of organic carbon (OC) vulnerable to enhanced warming and subsequent release by both fluvial and coastal erosion processes. However, the rate of release, its behaviour in the Arctic Ocean and vulnerability to remineralisation is poorly understood. Here we combine new measurements of microbial biohopanoids including adenosylhopane, a lipid associated with soil microbial communities, with published glycerol dialkyl glycerol tetraethers (GDGTs) and bulk δ13C measurements to improve knowledge of the fate of OC transported to the East Siberian Arctic Shelf (ESAS). The microbial hopanoid-based soil OC proxy Rsoil ranges from 0.0 to 0.8 across the ESAS, with highest values nearshore and decreases offshore. Across the shelf Rsoil displays a negative linear correlation with bulk δ13C measurements (r2 = −0.73, p =  < 0.001). When compared to the GDGT-based OC proxy, the branched and isoprenoid tetraether (BIT) index, a decoupled (non-linear) behaviour on the shelf was observed, particularly in the Buor-Khaya Bay, where the Rsoil shows limited variation, whereas the BIT index shows a rapid decline moving away from the Lena River outflow channels. This reflects a balance between delivery and removal of OC from different sources. The good correlation between the hopanoid and bulk terrestrial signal suggests a broad range of hopanoid sources, both fluvial and via coastal erosion, whilst GDGTs appear to be primarily sourced via fluvial transport. Analysis of ice complex deposits (ICDs) revealed an average Rsoil of 0.5 for the Lena Delta, equivalent to that of the Buor-Khaya Bay sediments, whilst ICDs from further east showed higher values (0.6–0.85). Although Rsoil correlates more closely with bulk OC than the BIT, our understanding of the endmembers of this system is clearly still incomplete, with variations between the different East Siberian Arctic regions potentially reflecting differences in environmental conditions (e.g. temperature, pH), but other physiological controls on microbial bacteriohopanepolyol (BHP) production under psychrophilic conditions are as yet unknown.

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The Arctic contains a large pool of carbon that is vulnerable to warming and can be released by rivers and coastal erosion. We study microbial lipids (BHPs) in permafrost and shelf sediments to trace the source, transport and fate of this carbon. BHPs in permafrost deposits are released to the shelf by rivers and coastal erosion, in contrast to other microbial lipids (GDGTs) that are transported by rivers. Several further analyses are needed to understand the complex East Siberian Shelf system.
The Arctic contains a large pool of carbon that is vulnerable to warming and can be released by...
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