Terrestrial Organic Matter Contributes to CO2 Production From Siberian Shelf Sediments

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Author(s)Sauerland, Lewis
Author(s)Ray, Nicholas
Author(s)Martens, Jannik
Author(s)Tesi, Tommaso
Author(s)Dudarev, Oleg
Author(s)Gustafsson, Örjan
Author(s)Semiletov, Igor
Author(s)Wild, Birgit
Date Accessioned2025-01-10T20:23:07Z
Date Available2025-01-10T20:23:07Z
Publication Date2025-01-01
DescriptionThis article was originally published in Journal of Geophysical Research: Biogeosciences. The version of record is available at: https://doi.org/10.1029/2024JG008226. © 2025. The Author(s). This is an open access article under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/4.0/), which permits use, distribution and reproduction in any medium, provided the original work is properly cited.
AbstractArctic climate warming is causing permafrost thaw and erosion, which may lead to enhanced inputs of terrestrial organic matter into Arctic Ocean shelf sediments. Degradation of terrestrial organic matter in sediments might contribute to carbon dioxide production and bottom water acidification. Yet, the degradability of organic matter in shallow Arctic Ocean sediments, as well as the contribution of terrestrial input, is poorly quantified. Here, potential organic matter degradation rates were investigated for 16 surface sediments from the Kara Sea, Laptev Sea, and the western East Siberian Sea and compared with physicochemical sediment properties including molecular biomarkers, stable and radioactive carbon isotopes, and grain size. Aerobic oxygen and carbon dioxide fluxes, measured in laboratory incubations of sediment slurry, showed high spatial variability and correlated significantly with organic carbon content as well as with the amount and degradation state of terrestrial organic matter. The dependency on terrestrial organic matter declined with increasing distance from land, indicating that the presence of terrestrial organic matter is likely a constraining factor for organic matter degradation in shallow shelf seas. However, sediment oxygen consumption rates, measured in incubations of intact sediment cores, also exhibited substantial spatial variability but were not related to organic carbon content or terrestrial influence. Oxygen consumption of intact sediments may be more strongly influenced by in situ redox conditions. Together with previous observations, our findings support that terrestrial organic matter is easily degradable in shelf sea sediments and might substantially contribute to aerobic carbon dioxide production and oxygen consumption. Plain Language Summary The Arctic climate is warming rapidly, which is leading to thawing of frozen deposits on land. These deposits contain large amounts of terrestrial organic matter that is being eroded and deposited into shallow ocean sediments. The breakdown of terrestrial organic matter in sediments might contribute to carbon dioxide release into the ocean water. There is insufficient knowledge on how fast this breakdown is happening and which parameters influence it. We investigated organic matter breakdown rates for sediment samples taken from shallow Siberian seas and compared them with sediment properties. Oxygen consumption and carbon dioxide release were measured in laboratory experiments and showed high variability between different samples. The release was related to the amount of terrestrial organic matter and its state of decomposition. This relationship decreased strongly for sediments further away from land. During a second incubation experiment, using intact sediment cores, oxygen consumption rates were measured and also showed high variability between samples. Oxygen consumption rates were not related to organic matter content. These findings support previous observations that terrestrial organic matter breaks down rapidly in shallow Arctic Ocean sediments and might also substantially contribute to the release of carbon dioxide and consumption of oxygen from the seawater. Key Points - Carbon dioxide fluxes from sediment slurry incubations showed high variability and were dependent on the input of terrestrial organic matter - Pronounced variability in oxygen consumption of intact sediment cores could not be explained by the input of terrestrial organic matter
SponsorWe thank the scientific team and the crew of the ISSS-2020 expedition, as well as Draupnir Einarsson (Stockholm University) for developing the core incubation setup. The work was funded by the Swedish Research Council VR (Grants 2018-05489 and 2021-01750 to B.W., 2021–06670 to J.M., and 2017-01601 to Ö.G.), the Swedish Research Council for Sustainable Development (Formas) (Grant 2018-01547 to B.W.), the Carl Trygger Foundation (Grant CTS 20: 470 to B.W.) and the European Research Council (ERC-AdG CC-Top, Grant 695331 to Ö.G.). The field work was supported by the Russian Science Foundation (Grant 21-77-30001 to I.S.), with additional support from the Ministry of Science and Higher Education of the Russian Federation (Grant “Priority-2030”, SakhGU and by Grant FEFF-2024-0004, SakhGU). The ship charter of the R/V Akademik Mstislav Keldysh was funded by Grant 121021500057-4 (POI), and by Grant “Priority-2030” (TGU) from the Ministry of Science and Higher Education of the Russian Federation.
CitationSauerland, L., Ray, N., Martens, J., Tesi, T., Dudarev, O., Gustafsson, Ö., et al. (2025). Terrestrial organic matter contributes to CO2 production from Siberian shelf sediments. Journal of Geophysical Research: Biogeosciences, 130, e2024JG008226. https://doi.org/10.1029/2024JG008226
ISSN2169-8961
URLhttps://udspace.udel.edu/handle/19716/35713
Languageen_US
PublisherJournal of Geophysical Research: Biogeosciences
dc.rightsAttribution 4.0 Internationalen
dc.rights.urihttp://creativecommons.org/licenses/by/4.0/
Keywordssediment CO2 release
Keywordssediment O2 consumption
Keywordsmolecular biomarkers
KeywordsLaptev Sea
KeywordsKara Sea
KeywordsEast Siberian Sea
TitleTerrestrial Organic Matter Contributes to CO2 Production From Siberian Shelf Sediments
TypeArticle
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