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Methane in Lakes: Variability in Stable Carbon Isotopic Composition and the Potential Importance of Groundwater Input

Schenk, Jonathan and Sawakuchi, Henrique O. and Sieczko, Anna K. and Pajala, Gustav and Rudberg, David and Hagberg, Emelie and Fors, Kjell and Laudon, Hjalmar and Karlsson, Jan and Bastviken, David (2021). Methane in Lakes: Variability in Stable Carbon Isotopic Composition and the Potential Importance of Groundwater Input. . 9 , 722215
[Research article]

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Abstract

Methane (CH4) is an important component of the carbon (C) cycling in lakes. CH4 production enables carbon in sediments to be either reintroduced to the food web via CH4 oxidation or emitted as a greenhouse gas making lakes one of the largest natural sources of atmospheric CH4. Large stable carbon isotopic fractionation during CH4 oxidation makes changes in C-13:C-12 ratio (delta C-13) a powerful and widely used tool to determine the extent to which lake CH4 is oxidized, rather than emitted. This relies on correct delta C-13 values of original CH4 sources, the variability of which has rarely been investigated systematically in lakes. In this study, we measured delta C-13 in CH4 bubbles in littoral sediments and in CH4 dissolved in the anoxic hypolimnion of six boreal lakes with different characteristics. The results indicate that delta C-13 of CH4 sources is consistently higher (less C-13 depletion) in littoral sediments than in deep waters across boreal and subarctic lakes. Variability in organic matter substrates across depths is a potential explanation. In one of the studied lakes available data from nearby soils showed correspondence between delta C-13-CH4 in groundwater and deep lake water, and input from the catchment of CH4 via groundwater exceeded atmospheric CH4 emissions tenfold over a period of 1 month. It indicates that lateral hydrological transport of CH4 can explain the observed delta C-13-CH4 patterns and be important for lake CH4 cycling. Our results have important consequences for modelling and process assessments relative to lake CH4 using delta C-13, including for CH4 oxidation, which is a key regulator of lake CH4 emissions.

Authors/Creators:Schenk, Jonathan and Sawakuchi, Henrique O. and Sieczko, Anna K. and Pajala, Gustav and Rudberg, David and Hagberg, Emelie and Fors, Kjell and Laudon, Hjalmar and Karlsson, Jan and Bastviken, David
Title:Methane in Lakes: Variability in Stable Carbon Isotopic Composition and the Potential Importance of Groundwater Input
Year of publishing :2021
Volume:9
Article number:722215
Number of Pages:15
Publisher:FRONTIERS MEDIA SA
Language:English
Publication Type:Research article
Article category:Scientific peer reviewed
Version:Published version
Copyright:Creative Commons: Attribution 4.0
Full Text Status:Public
Subjects:(A) Swedish standard research categories 2011 > 1 Natural sciences > 105 Earth and Related Environmental Sciences > Oceanography, Hydrology, Water Resources
Keywords:stable carbon isotope, methane, lake, groundwater, endmember
URN:NBN:urn:nbn:se:slu:epsilon-p-114447
Permanent URL:
http://urn.kb.se/resolve?urn=urn:nbn:se:slu:epsilon-p-114447
Additional ID:
Type of IDID
DOI10.3389/feart.2021.722215
Web of Science (WoS)000717647200001
ID Code:26226
Faculty:S - Faculty of Forest Sciences
Department:(S) > Dept. of Forest Ecology and Management
Deposited By: SLUpub Connector
Deposited On:29 Nov 2021 10:25
Metadata Last Modified:29 Nov 2021 10:31

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