Transformation of organic matter in a Barents Sea sediment profile: coupled geochemical and microbiological processes

Mark Stevenson*, Johan Faust, Felipe Sales De Freitas, Luiza Andrade, Neil Grey, Karen Tait, Katharine Hendry, Robert Hilton, Sian Henley, Allyson Tessin, Peter Leary, Sonia Papadaki, Ailbe Ford, Christian Maerz, Geoffrey Abbott

*Corresponding author for this work

Research output: Contribution to journalArticle (Academic Journal)peer-review

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Abstract

Process-based, mechanistic investigations of organic matter transformation and diagenesis directly beneath the sediment–water interface (SWI) in Arctic continental shelves are vital as these regions are at greatest risk of future change. This is in part due to disruptions in benthic–pelagic coupling associated with ocean current change and sea ice retreat. Here, we focus on a high-resolution, multi-disciplinary set of measurements that illustrate how microbial processes involved in the degradation of organic matter are directly coupled with inorganic and organic geochemical sediment properties (measured and modelled) as well as the extent/depth of bioturbation. We find direct links between aerobic processes, reactive organic carbon and highest abundances of bacteria and archaea in the uppermost layer (0–4.5 cm depth) followed by dominance of microbes involved in nitrate/nitrite and iron/manganese reduction across the oxic-anoxic redox boundary (approx. 4.5–10.5 cm depth). Sulfate reducers dominate in the deeper (approx. 10.5–33 cm) anoxic sediments which is consistent with the modelled reactive transport framework. Importantly, organic matter reactivity as tracked by organic geochemical parameters (n-alkanes, n-alkanoic acids, n-alkanols and sterols) changes most dramatically at and directly below the SWI together with sedimentology and biological activity but remained relatively unchanged across deeper changes in sedimentology.
Original languageEnglish
Article number 20200223
Number of pages22
JournalPhilosophical Transactions of the Royal Society A: Physical and Engineering Sciences
Volume378
Issue number2181
Early online date31 Aug 2020
DOIs
Publication statusPublished - 2 Oct 2020

Keywords

  • Barents sea
  • carbon cycling
  • microbial processes
  • geochemistry
  • marine sediment
  • organic matter reactivity

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