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https://doi.org/10.5194/bg-2019-144
© Author(s) 2019. This work is distributed under
the Creative Commons Attribution 4.0 License.
https://doi.org/10.5194/bg-2019-144
© Author(s) 2019. This work is distributed under
the Creative Commons Attribution 4.0 License.

Research article 06 May 2019

Research article | 06 May 2019

Review status
This discussion paper is a preprint. It is a manuscript under review for the journal Biogeosciences (BG).

Microbial community composition and abundance after millennia of submarine permafrost warming

Julia Mitzscherling1, Fabian Horn1, Maria Winterfeld2, Linda Mahler1, Jens Kallmeyer1, Pier Paul Overduin3, Lutz Schirrmeister3, Matthias Winkel4, Mikhail N. Grigoriev5, Dirk Wagner1,6, and Susanne Liebner1,7 Julia Mitzscherling et al.
  • 1GFZ German Research Centre for Geosciences, Helmholtz Centre Potsdam, Section 3.7 Geomicrobiology, 14473 Potsdam, Germany
  • 2Alfred Wegener Institute, Helmholtz Centre for Polar and Marine Research, Marine Geochemistry, 27570 Bremerhaven, Germany
  • 3Alfred Wegener Institute, Helmholtz Centre for Polar and Marine Research, Permafrost Research, 14473 Potsdam, Germany
  • 4GFZ German Research Centre for Geosciences, Helmholtz Centre Potsdam, Section 3.5 Interface Geochemistry, 14473 Potsdam, Germany
  • 5Siberian Branch, Russian Academy of Sciences, Mel’nikov Permafrost Institute, Yakutsk, Russia
  • 6University of Potsdam, Institute of Geosciences, 14476 Potsdam, Germany
  • 7University of Potsdam, Institute of Biochemistry and Biology, 14476 Potsdam, Germany

Abstract. Warming of the Arctic led to an increase of permafrost temperatures by about 0.3 °C during the last decade. Permafrost warming is associated with increasing sediment water content, permeability and diffusivity and could on the long-term alter microbial community composition and abundance even before permafrost thaws. We studied the long-term effect (up to 2500 years) of submarine permafrost warming on microbial communities along an onshore-offshore transect on the Siberian Arctic Shelf displaying a natural temperature gradient of more than 10 °C. We analysed the in-situ development of bacterial abundance and community composition through total cell counts (TCC), quantitative PCR of bacterial gene abundance and amplicon sequencing, and correlated the microbial community data with temperature, pore water chemistry and sediment physicochemical parameters. On time-scales of centuries, permafrost warming coincided with an overall decreasing microbial abundance while millennia after warming microbial abundance was similar to cold onshore permafrost and DOC content was least. Based on correlation analysis TCC unlike bacterial gene abundance showed a significant rank-based negative correlation with increasing temperature while both TCC and bacterial gene copy numbers showed a negative correlation with salinity. Bacterial community composition correlated only weakly with temperature but strongly with pore-water stable isotope signatures and depth, while it showed no correlation with salinity. Microbial community composition showed substantial spatial variation and an overall dominance of Actinobacteria, Chloroflexi, Firmicutes, Gemmatimonadetes and Proteobacteria which are amongst the microbial taxa that were found to be active in other frozen permafrost environments as well. We suggest that, millennia after permafrost warming by over 10 °C, microbial community composition and abundance show some indications for proliferation but mainly reflect the sedimentation history and paleo-environment and not a direct effect through warming.

Julia Mitzscherling et al.
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Julia Mitzscherling et al.
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Pore water chemistry, grain sizes and sediment temperature of 4 sediment cores from submarine permafrost at Mamontov Klyk Cape, Laptev Sea shelf J. Mitzscherling, F. Horn, M. Winterfeld, L. Mahler, J. Kallmeyer, P. P. Overduin, M. Winkel, M. N. Grigoriev, D. Wagner, and S. Liebner https://doi.pangaea.de/10.1594/PANGAEA.895292

Julia Mitzscherling et al.
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Short summary
Permafrost temperatures increased substantially at a global scale potentially altering microbial assemblages involved in carbon mobilization before permafrost thaws. We used submarine permafrost of the Arctic Shelf as natural laboratory to investigate the microbial response to long-term permafrost warming. Our work shows that millennia after permafrost warming by > 10 °C microbial community composition and population size reflect the paleo-environment rather than a direct effect through warming.
Permafrost temperatures increased substantially at a global scale potentially altering microbial...
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