Millennial scale persistence of organic carbon bound to iron in Arctic marine sediments

• Published in: Nature Communications
• Main Authors: Faust, Johan C, Tessin, Allyson, Fisher, Ben J, Zindorf, Mark, Papadaki, Sonia, Hendry, Katharine R, Doyle, Katherine A, März, Christian
• Format: Article in Journal/Newspaper
• Language: English
• Published: 2021
• Subjects: Barents Sea; geochemical sediment composition; carbon cycle; Arctic Ocean; pore water chemistry; reactive iron and manganese; redox boundary; Arctic
• Online Access: https://hdl.handle.net/1983/bf9455b5-58d7-4a66-a91a-b51fab606437; https://research-information.bris.ac.uk/en/publications/bf9455b5-58d7-4a66-a91a-b51fab606437; https://doi.org/10.1038/s41467-020-20550-0; https://research-information.bris.ac.uk/ws/files/272694977/s41467_020_20550_0.pdf

Burial of organic material in marine sediments represents a dominant natural mechanism of long-term carbon sequestration globally, but critical aspects of this carbon sink remain unresolved. Investigation of surface sediments led to the proposition that on average 10-20% of sedimentary organic carbon is stabilised and physically protected against microbial degradation through binding to reactive metal (e.g. iron and manganese) oxides. Here we examine the long-term efficiency of this rusty carbon sink by analysing the chemical composition of sediments and pore waters from four locations in the Barents Sea. Our findings show that the carbon-iron coupling persists below the uppermost, oxygenated sediment layer over thousands of years. We further propose that authigenic coprecipitation is not the dominant factor of the carbon-iron bounding in these Arctic shelf sediments and that a substantial fraction of the organic carbon is already bound to reactive iron prior deposition on the seafloor.