New evidence for preservation of contemporary marine organic carbon by iron in Arctic shelf sediments

• Published in: Environmental research letters Vol. 18; no. 1; pp. 14006 - 14017
• Main Authors: Faust, Johan C, Ascough, Philippa, Hilton, Robert G, Stevenson, Mark A, Hendry, Katharine R, März, Christian
• Format: Journal Article
• Language: English
• Published: Bristol IOP Publishing 01.01.2023
• Subjects: Age; Barents Sea; Carbon; carbon isotopes; carbon sequestration; Iron; Isotopes; Lability; Marine sediments; marine shelf sediments; Minerals; OC-Fe; Organic carbon; Organic matter; Polar environments; radiocarbon; Sediments; Shelving; Stable isotopes; Arctic region
• ISSN: 1748-9326; 1748-9326
• DOI: 10.1088/1748-9326/aca780

Abstract The protection of organic carbon through association with iron minerals (Fe R ) is an important factor in its stabilisation, long-term storage, and burial efficiency in marine sediments. However, large uncertainties still exist concerning the sources, lability, age, and composition of the organic matter associated with Fe R in natural sediments. Therefore, the timing and environmental setting of the carbon-iron bonding process remain elusive. Here we use radiocarbon (Δ 14 C) and stable isotopes (δ 13 C) of downcore bulk sedimentary organic matter, benthic foraminifera and the organic carbon fraction bound to Fe R to interrogate the source and age of the organic carbon pool associated with Fe R in Arctic marine sediments. In the Barents Sea, we find that the organic carbon associated with Fe R is younger overall than the bulk organic matter and is probably marine derived. The comparison to other investigations of OC-Fe R origins reveals that in large parts of Arctic shelf regions Fe R associated organic carbon is radiocarbon enriched and has a higher δ 13 C org value compared to the bulk sediment, irrespective of sediment depth/age. Our findings suggest a rapid and preferential binding of fresh and marine organic matter with Fe R . Hence, labile organic matter prone to decomposition is protected and stabilised, underlining the potential of the organic carbon–iron association as an efficient carbon burial mechanism.