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 Sebastian, Papadaki, Sonia, Hendry, Katharine R., Doyle, Katherine A., März, Christian
• Format: Text
• Language: English
• Published: Springer Science and Business Media LLC
• Subjects: envir; archeo; Arctic; Barents Sea
• Online Access: https://doi.org/10.1038/s41467-020-20550-0; https://archimer.ifremer.fr/doc/00675/78755/80923.pdf; https://archimer.ifremer.fr/doc/00675/78755/80924.pdf; https://archimer.ifremer.fr/doc/00675/78755/80925.pdf; https://archimer.ifremer.fr/doc/00675/78755/80926.pdf; https://archimer.ifremer.fr/doc/00675/78755/80927.xlsx

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.