Production of Ancient Dissolved Organic Carbon in Arctic Ocean Sediment: A Pathway of Carbon Cycling in the Extreme Environment
Wenjing Fu, Yuanzhi Qi, Yanguang Liu, Xuchen Wang, Ellen R. M. Druffel, Xiaomei Xu, Peng Ren, Shuwen Sun, Di Fan
Abstract
Abstract We report quantitative carbon isotope evidence showing that porewater dissolved organic carbon (DOC) is produced from different sources in Arctic Ocean sediments, resulting in dramatic changes in both δ 13 C and Δ 14 C values of DOC. The very low δ 13 C (−42.7‰) and Δ 14 C (−947‰) values measured for porewater DOC indicate that bacteria consume methane hydrate‐derived OC and convert a significant fraction of this δ 13 C depleted and old OC (44–97%) into DOC in the sediments of the Arctic Ocean. We suggest that the production of extremely old, methane‐derived porewater DOC (5,430–23,600 years) in Arctic Ocean sediment is an important pathway for carbon cycling that provides not only a necessary energy source for microbial communities in this extreme environment but also an ancient DOC source that could flux and contribute to the old and biologically recalcitrant DOC found in the deep ocean.