Department of Biology

Aarhus University Seal / Aarhus Universitets segl

Bo Barker Jørgensen

Sub-seafloor biogeochemical processes and microbial life in the Baltic Sea

Research output: Contribution to journal/Conference contribution in journal/Contribution to newspaperReviewResearchpeer-review

DOI

The post-glacial Baltic Sea has experienced extreme changes that are archived today in the deep sediments. IODP Expedition 347 retrieved cores down to 100 m depth and studied the climate history and the deep biosphere. We here review the biogeochemical and microbiological highlights and integrate these with other studies from the Baltic seabed. Cell numbers, endospore abundance and organic matter mineralization rates are extremely high. A 100-fold drop in cell numbers with depth results from a small difference between growth and mortality in the ageing sediment. Evidence for growth derives from a D:L amino acid racemization model, while evidence for mortality derives from the abundance and potential activity of lytic viruses. The deep communities assemble at the bottom of the bioturbated zone from the founding surface community by selection of organisms suited for life under deep sediment conditions. The mean catabolic per-cell rate of microorganisms drops steeply with depth to a life in slow-motion, typical for the deep biosphere. The subsurface life under extreme energy limitation is facilitated by exploitation of recalcitrant substrates, by biochemical protection of nucleic acids and proteins and by repair mechanisms for random mismatches in DNA or damaged amino acids in proteins.

Original languageEnglish
JournalEnvironmental Microbiology
Volume22
Issue5
Pages (from-to)1688-1706
Number of pages19
ISSN1462-2912
DOIs
Publication statusPublished - May 2020

    Research areas

  • AARHUS BAY, ANAEROBIC OXIDATION, ARCHAEA, ARKONA BASIN, LANDSORT DEEP, METHANE PRODUCTION, SUBSURFACE SEDIMENTS, SULFATE-REDUCING BACTERIA, SULFUR CYCLE, VIRAL IMPACT

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