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Influence of water column stratification and mixing patterns on the fate of methane produced in deep sediments of a small eutrophic lake
Author(s) -
Vachon Dominic,
Langenegger Timon,
Donis Daphne,
McGinnis Daniel F.
Publication year - 2019
Publication title -
limnology and oceanography
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.7
H-Index - 197
eISSN - 1939-5590
pISSN - 0024-3590
DOI - 10.1002/lno.11172
Subject(s) - hypolimnion , epilimnion , water column , eutrophication , environmental science , methane , environmental chemistry , stratification (seeds) , hydrology (agriculture) , atmospheric sciences , chemistry , oceanography , geology , nutrient , biology , seed dormancy , germination , botany , geotechnical engineering , dormancy , organic chemistry
Methane (CH 4 ), a potent greenhouse gas, is produced in and emitted from lakes at globally significant rates. The drivers controlling the proportion of produced CH 4 that will reach the atmosphere, however, are still not well understood. We sampled a small eutrophic lake (Soppensee, Switzerland) in 2016–2017 for CH 4 concentrations profiles and emissions, combined with water column hydrodynamics to investigate the fate of CH 4 produced in hypolimnetic sediments. Using a mass balance approach for the periods between April and October of both years, net CH 4 production rates in hypolimnetic sediments ranged between 11.4 and 17.7 mmol m −2 d −1 , of which 66–88% was stored in the hypolimnion, 13–27% was diffused to the epilimnion, and 6–7% left the sediments via ebullition. Combining these results with a process‐based model we show that water column turbulent diffusivity ( K z ) had a major influence on the fate of produced CH 4 in the sediments, where higher K z values potentially lead to greater proportion being oxidized and lower K z lead to a greater proportion being stored. During fall when the water column mixes, we found that a greater proportion of stored CH 4 is emitted if the lake mixes rapidly, whereas a greater proportion will be oxidized if the water column mixes more gradually. This work highlights the central role of lake hydrodynamics in regulating CH 4 dynamics and further suggests the potential for CH 4 production and emissions to be sensitive to climate‐driven alterations in lake mixing regimes and stratification.

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