For more a decade scientists at the Max Planck Institute for Marine Microbiology and their colleagues at MARUM and the University of Aarhus have investigated microbial life from this habitat.
The samples were taken during the Ocean Drilling Program (ODP) in 2002. (www-odp.tamu.edu).
The international drilling vessel JOIDES Resolution
This “Deep Biosphere”, reaching several hundred meters below the seafloor, is exclusively inhabited by microbes and is generally considered as stable. Nevertheless, only little is known about how this system developed over millennia and how this microbial life influences the cycling of carbon in the oceans.
In a new study appearing in the Proceedings of the National Academy of Sciences (PNAS) Dr. Sergio Contreras, a palaeoceanographer, and his Bremen colleagues use a careful examination of drill-cores from the continental shelf of Peru to actually show how surprisingly dynamic this deeply buried ecosystem can be.
Below the sea floor, consortia of two different domains of microorganisms (archaea and bacteria) tap the energy of methane, which they oxidize by using sulfate. This process is known as the anaerobic oxidation of methane (AOM) and has been intensively studied by Bremen researchers. Methane, also produced by archaea, emerges from deeper layers of the sediment, while sulfate diffuses slowly from the water column into the sediment.
Both reactants meet at the so-called methane oxidation front. Only at this front are concentrations of sulfate and methane high enough for the microbial turnover to take place, and here the AOM process leaves behind mineral and biological fossil signatures. For example, archaeol, a constituent of the archaeal cell membrane, is an extremely stable molecule that is preserved over thousands to millions of years. Minerals such as barite (barium sulfate) and dolomite (magnesium calcium carbonate) also precipitate at this methane oxidation front due to microbial activity.Migration of the methane oxidation front
The geologist Dr. Patrick Meister highlights the implications of this finding: „The detected traces provide the key to the history of the sub-seafloor microbial activity and its dynamic interaction with climate and oceanography for of the past 100,000 years. If we look further back in time, such as over the past million years” speculates Meister, “we might find even more drastic changes of microbial activity in the deep biosphere“. Such ongoing research efforts between geologists and microbiologists, along with access to deep sediment samples within the framework of the Integrated Ocean Drilling Program (IODP), should continue to provide insight into the interactions between climate and the deep biosphere.
Further InformationenDr. Patrick Meister, +49 421 2028832, email@example.com
doi/10.1073/pnas.1305981110Institutes and Universities
Organic Geochemistry Group, MARUM - Center for Marine Environmental Sciences & Department of Geosciences, University of Bremen, D-28359 Bremen, Germany
Department of Bioscience, Center for Geomicrobiology, Aarhus University, Ny Munkegade 116, 8000 Aarhus C, Denmark.
Dr. Manfred Schloesser | Max-Planck-Institut
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