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

• Published in: Environmental Research Letters
• Main Authors: Johan C Faust, Philippa Ascough, Robert G Hilton, Mark A Stevenson, Katharine R Hendry, Christian März
• Format: Article in Journal/Newspaper
• Language: English
• Published: IOP Publishing 2022
• Subjects: Barents Sea; OC-Fe; marine shelf sediments; radiocarbon; carbon isotopes; carbon sequestration; Environmental technology. Sanitary engineering; TD1-1066; Environmental sciences; GE1-350; Science; Q; Physics; QC1-999; Arctic; Foraminifera*
• Online Access: https://doi.org/10.1088/1748-9326/aca780; https://doaj.org/article/46f586e8c86246e3aa177ef163062227

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.