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Lookup NU author(s): Dr Juliane Bischoff, Dr Rob Spencer, Dr Helen Talbot
This work is licensed under a Creative Commons Attribution 4.0 International License (CC BY 4.0).
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 delta C-13 measurements to improve knowledge of the fate of OC transported to the East Siberian Arctic Shelf (ESAS). The microbial hopanoid-based soil OC proxy R'(soil) ranges from 0.0 to 0.8 across the ESAS, with highest values nearshore and decreases offshore. Across the shelf R'(soil) displays a negative linear correlation with bulk delta C-13 measurements (r(2) = -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 R'(soil) 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 R'(soil) 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 R'(soil) 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.
Author(s): Bischoff J, Sparkes RB, Selver AD, Spencer RGM, Gustafsson O, Semiletov IP, Dudarev OV, Wagner D, Rivkina E, van Dongen BE, Talbot HM
Publication type: Article
Publication status: Published
Journal: Biogeosciences
Year: 2016
Volume: 13
Issue: 17
Pages: 4899-4914
Online publication date: 10/08/2016
Acceptance date: 10/08/2016
Date deposited: 11/11/2016
ISSN (print): 1726-4170
ISSN (electronic): 1726-4189
Publisher: Copernicus GmbH
URL: http://dx.doi.org/10.5194/bg-13-4899-2016
DOI: 10.5194/bg-13-4899-2016
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