EGU General Assembly 2022
© Author(s) 2022. This work is distributed under
the Creative Commons Attribution 4.0 License.

Biological sulfate reduction in deep subseafloor sediment of Guaymas Basin

Toshiki Nagakura1, Florian Schubert1, Jens Kallmeyer1, and the IODP Exp. 385 Scientists*
Toshiki Nagakura et al.
  • 1GFZ German Research Centre for Geosciences, Geomicrobiology, Germany (
  • *A full list of authors appears at the end of the abstract

Sulfate reduction is the quantitatively most important process to degrade organic matter in anoxic marine sediment and has been studied intensively in a variety of settings. Guaymas Basin, a young marginal ocean basin, offers the unique opportunity to study sulfate reduction in an environment characterized by organic-rich sediment, high sedimentation rates, and high geothermal gradients (100-958°C km-1). We measured sulfate reduction rates (SRR) in samples of the International Ocean Discovery Program (IODP) Expedition 385 using incubation experiments with radiolabeled 35SO42- carried out at in-situ pressure and temperature. Site U1548C, outside of a circular hydrothermal mound above a hot sill intrusion (Ringvent), has the highest geothermal gradient (958°C km-1) of all eight sampling sites. In near-surface sediment from this site, we measured the highest SRR (387 nmol cm-3 d-1) of all samples from this expedition. At Site U1548C SRR were generally over an order of magnitude higher than at similar depths at other sites. Site U1546D also had a sill intrusion, but it had already reached thermal equilibrium and SRR were in the same range as nearby Site U1545C, which is minimally affected by sills. The wide temperature range found in the stratigraphic section at each drill site leads to major shifts in microbial community composition with very different temperature optima. At the transition between the mesophilic and thermophilic range around 40 to 60°C, sulfate-reducing activity appears to be decreased, particularly in more oligotrophic settings but shows a slight recovery at higher temperatures.

IODP Exp. 385 Scientists:

Andreas P. Teske; Daniel Lizarralde; Tobias W. Höfig; Ivano W. Aiello; Janine L. Ash; Diana P. Bojanova; Martine Buatier; Virginia P. Edgcomb; Christophe Y. Galerne; Swanne Gontharet; Verena B. Heuer; Shijun Jiang; Myriam A.C. Kars; Ji-Hoon Kim; Louise M.T. Koornneef; Kathleen M. Marsaglia; Nicolette R. Meyer; Yuki Morono; Raquel Negrete-Aranda; Florian Neumann; Lucie C. Pastor; Manet Peña-Salinas; Ligia L. Pérez Cruz; Lihua Ran; Armelle Riboulleau; John A. Sarao; Florian Schubert; S. Khogenkumar Singh; Joann M. Stock; Laurent M.A.A. Toffin; Wei Xie; Toshiro Yamanaka; Guangchao Zhuang

How to cite: Nagakura, T., Schubert, F., and Kallmeyer, J. and the IODP Exp. 385 Scientists: Biological sulfate reduction in deep subseafloor sediment of Guaymas Basin, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-2525,, 2022.


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