Project: Characteristics and extent of microbial anaerobic methane oxidation and sulfate reduction in the deep terrestrial subsurface over geological time scales

Recent discoveries indicate that methane consumption by microorganisms occurs in the deep crystalline bedrock – one of the least understood ecosystems on Earth. This study will answer fundamental questions related to past and present microbial methane consumption within the bedrock, including the geochemical prerequisites, continuity, and extent of the process.

Project information

Project manager
Henrik Drake
Vetenskapsrådet (the Swedish Research Council)
1 Jan 2018-31 Dec 2021
(Department of Biology and Environmental Science, Faculty of Health and Life Sciences)

More about the project

The release of the greenhouse gas methane to the atmosphere from terrestrial sources is mitigated by aerobic and anaerobic oxidation of the gas. Sulfate-dependent anaerobic microbial oxidation of methane (AOM) typically occurs in near-surface environments such as organic-rich marine sediments. Precipitation of 13C-depleted carbonate is a tracer of AOM in these environments.

Recent discoveries of extremely 13C-depleted carbonates deep in fractured crystalline rocks indicate that AOM occurs also here, in one of the least understood ecosystem on Earth. Several critical questions of AOM in this setting remain unanswered and include:

  • Is this previously unknown deep sink for methane spatially and temporally widespread in the continental crystalline crust?
  • What physicochemical conditions and nutrient/methane sources characterise these deep microbial processes?
  • What causes the associated uniquely large carbon and sulfur isotope variability?

To address these questions, coupled state-of-the-art micro-scale techniques for isotopic measurements, radiometric dating and detection of organic compounds within fine-grained subsurface minerals will be used along with spatially related gas and water data. The samples represent a wide variety sites (in Sweden, Finland and Greenland) and depths (down to 2.5 km) within the crust. The results will answer fundamental questions related to past and present microbial processes within the bedrock, in particular regarding methane consumption.

The project is related to the project Production and consumption of the greenhouse gas methane in the crystalline bedrock.