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

• Published in: Biogeosciences
• Main Authors: Bischoff, Juliane, Sparkes, Robert B., Selver, Ayça Doğrul, Gustafsson, Orjan, Semiletov, Igor P., Dudarev, Oleg V., Wagner, Dirk, Rivkina, Elizaveta
• Other Authors: Mühendislik Fakültesi, orcid:0000-0001-7949-8056, orcid:0000-0003-0756-0150, orcid:0000-0001-5064-497X, orcid:0000-0003-1189-142X
• Format: Article in Journal/Newspaper
• Language: English
• Published: Copernicus Gesellschaft MBH 2016
• Subjects: Dialkyl Glycerol Tetraethers; Suspended Particulate Matter; Trap Mass-Spectrometry; Buor-Khaya Bay; Bacterial; Arctic; Arctic Ocean; Buor-Khaya; Khaya; lena delta; lena river; Swedish Polar Research Secretariat
• Online Access: https://hdl.handle.net/20.500.12462/6734; https://doi.org/10.5194/bg-13-4899-2016

Selver, Ayça Doğrul (Balikesir Author) 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. NERC Natural Environment Research Council NE/I024798/1 NE/I027967/1 Ministry of National Education - Turkey Swedish Royal Academy of Sciences through Knut and Alice Wallenberg Foundation Government of the Russian Federation 14 Z50.31.0012/03.19.2014 Russian Science Foundation (RSF) 15-17-20032 National Science Foundation (NSF) ANT-1203885/PLR-1500169 Knut & Alice Wallenberg Foundation Russian Academy of Sciences Swedish Research Council National Oceanic Atmospheric Admin (NOAA) - USA Russian Foundation for Basic Research (RFBR) Swedish Polar Research Secretariat Nordic Council of Ministers National Science Foundation (NSF) NERC Natural Environment Research Council NE/I024798/1 NE/I027967/1