Stabilization of mineral-associated organic carbon in Pleistocene permafrost

• Published in: Nature communications Vol. 14; no. 1; pp. 2120 - 8
• Main Authors: Martens, Jannik, Mueller, Carsten W., Joshi, Prachi, Rosinger, Christoph, Maisch, Markus, Kappler, Andreas, Bonkowski, Michael, Schwamborn, Georg, Schirrmeister, Lutz, Rethemeyer, Janet
• Format: Journal Article
• Language: English
• Published: London Nature Publishing Group UK 13.04.2023; Nature Publishing Group; Nature Portfolio
• Subjects: 140/131; 140/58; 704/106/47; 704/47/4112; 704/47/4113; Bioavailability; Biodegradation; Carbon; Carbon dioxide; Climate prediction; Decomposition; Emissions; Environmental changes; Environmental conditions; Greenhouse gases; Humanities and Social Sciences; Iron; Microbial degradation; Microorganisms; multidisciplinary; Occlusion; Organic carbon; Organic matter; Permafrost; Pleistocene; Science; Science (multidisciplinary); Sediments; Stabilization; Thawing
• ISSN: 2041-1723; 2041-1723
• DOI: 10.1038/s41467-023-37766-5

Ice-rich Pleistocene-age permafrost is particularly vulnerable to rapid thaw, which may quickly expose a large pool of sedimentary organic matter (OM) to microbial degradation and lead to emissions of climate-sensitive greenhouse gases. Protective physico-chemical mechanisms may, however, restrict microbial accessibility and reduce OM decomposition; mechanisms that may be influenced by changing environmental conditions during sediment deposition. Here we study different OM fractions in Siberian permafrost deposited during colder and warmer periods of the past 55,000 years. Among known stabilization mechanisms, the occlusion of OM in aggregates is of minor importance, while 33-74% of the organic carbon is associated with small, <6.3 µm mineral particles. Preservation of carbon in mineral-associated OM is enhanced by reactive iron minerals particularly during cold and dry climate, reflected by low microbial CO 2 production in incubation experiments. Warmer and wetter conditions reduce OM stabilization, shown by more decomposed mineral-associated OM and up to 30% higher CO 2 production. This shows that considering the stability and bioavailability of Pleistocene-age permafrost carbon is important for predicting future climate-carbon feedback. In ice-rich Siberian permafrost sediments deposited during the Pleistocene, 33-74% of the organic carbon is mineral-bound favoured by the presence of reactive iron, which can reduce microbial CO 2 production after thawing