EGU21-1030, updated on 02 Jun 2022
EGU General Assembly 2021
© Author(s) 2022. This work is distributed under
the Creative Commons Attribution 4.0 License.

Microbial utilization of terrigenous ancient carbon released to marine environments traced by compound specific radiocarbon dating

Manuel Ruben1,2, Florence Schubotz2,3, Hannah Marchant2,4, Jens Hefter1, Hendik Grotheer1, Matthias Forwick5, Witold Szczuciński6, and Gesine Mollenhauer1,2,3
Manuel Ruben et al.
  • 1Alfred-Wegener Institut, Marine Geoscience, Germany (
  • 2Universität Bremen, Bremen, Germany
  • 3MARUM, Bremen, Germany
  • 4Max-Plank Institute for Marine Microbiology, Bremen, Germany
  • 5UiT - The Arctic University of Norway, Tromsø, Norway
  • 6Adam Mickiewicz University, Poznań, Poland

Until two decades ago, ancient carbon was regarded as non-bioavailable substrate for organisms because it was synthesised, deposited, and once before (partially) degraded thousands to millions of years ago. Such aged organic matter is stored in terrestrial permafrost deposits or sedimentary bedrock, where it is locked up and remains disconnected from the active global carbon cycle. However, with changing climatic conditions, these organic matter reservoirs are being remobilised at faster rates by receding glaciers or permafrost thaw. During transport and after redeposition in newly formed sediments, the ancient carbon can be accessed by micro-organisms, but whether or not the micro-organisms can utilize the ancient carbon is highly debated.

Using a combined approach of lipid biomarker analysis, lipidology, and radiocarbon dating of bulk organic matter as well as single compounds targeting intact polar lipid fatty acids (IPL-FAs), our research demonstrates that microbial communities utilise supposedly non-bioavailable ancient carbon for biosynthesis in Arctic marine fjord sediments. The availability of ancient carbon to the sub-surface microbes represents a carbon source that has not been accounted for in today’s climate models. These implications are of major importance concerning the increased thawing of high latitude permafrost soils, permafrost mobilization and coastal erosion due to anthropogenic climate change, catalysing associated positive feedback loops. In future research, we will use this approach to study the utilization of ancient carbon derived from North American and Siberian permafrost soils in Arctic shelf sediments to assess its importance in the global carbon budgets.

How to cite: Ruben, M., Schubotz, F., Marchant, H., Hefter, J., Grotheer, H., Forwick, M., Szczuciński, W., and Mollenhauer, G.: Microbial utilization of terrigenous ancient carbon released to marine environments traced by compound specific radiocarbon dating, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-1030,, 2021.


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