title: Utilization of ancient permafrost carbon in headwaters of Arctic fluvial networks.
abstract: Northern high-latitude rivers are major conduits of carbon from land to coastal seas and the Arctic Ocean. Arctic warming is promoting terrestrial permafrost thaw and shifting hydrologic flowpaths, leading to fluvial mobilization of ancient carbon stores. Here we describe (14)C and (13)C characteristics of dissolved organic carbon from fluvial networks across the Kolyma River Basin (Siberia), and isotopic changes during bioincubation experiments. Microbial communities utilized ancient carbon (11,300 to >50,000 (14)C years) in permafrost thaw waters and millennial-aged carbon (up to 10,000 (14)C years) across headwater streams. Microbial demand was supported by progressively younger ((14)C-enriched) carbon downstream through the network, with predominantly modern carbon pools subsidizing microorganisms in large rivers and main-stem waters. Permafrost acts as a significant and preferentially degradable source of bioavailable carbon in Arctic freshwaters, which is likely to increase as permafrost thaw intensifies causing positive climate feedbacks in response to on-going climate change.
authors.affiliation: Department of Geography, Northumbria University, Newcastle Upon Tyne NE1 8ST, UK.
authors.forename: Paul J
authors.initials: PJ
authors.lastname: Mann
authors.affiliation: Department of Earth Sciences, Geological Institute, ETH Zürich, 8092 Zürich, Switzerland.
authors.forename: Timothy I
authors.initials: TI
authors.lastname: Eglinton
authors.affiliation: 1] Department of Earth Sciences, Geological Institute, ETH Zürich, 8092 Zürich, Switzerland [2] Department of Physics, Laboratory for Ion Beam Physics, ETH Zürich, 8093 Zürich, Switzerland.
authors.forename: Cameron P
authors.initials: CP
authors.lastname: McIntyre
authors.affiliation: North-East Science Station, Pacific Institute for Geography, Far-Eastern Branch of Russian Academy of Science, Cherskiy, Republic of Sakha (Yakutia), Russia.
authors.forename: Nikita
authors.initials: N
authors.lastname: Zimov
authors.affiliation: North-East Science Station, Pacific Institute for Geography, Far-Eastern Branch of Russian Academy of Science, Cherskiy, Republic of Sakha (Yakutia), Russia.
authors.forename: Anna
authors.initials: A
authors.lastname: Davydova
authors.affiliation: 1] Department of Earth Sciences, Utrecht University, Heidelberglaan 2, 3584 CS Utrecht, The Netherlands [2] Arctic Centre, University of Groningen, PO Box 716, 9700 AS Groningen, The Netherlands.
authors.forename: Jorien E
authors.initials: JE
authors.lastname: Vonk
authors.affiliation: Woods Hole Research Center, Falmouth, Massachusetts 02540, USA.
authors.forename: Robert M
authors.initials: RM
authors.lastname: Holmes
authors.affiliation: Department of Earth, Ocean and Atmospheric Science, Florida State University, Tallahassee, Florida 32306, USA.
authors.forename: Robert G M
authors.initials: RG
authors.lastname: Spencer