TY  - JOUR
A1  - Tang, Kam W.
A1  - McGinnis, Daniel F.
A1  - Frindte, Katharina
A1  - Bruchert, Volker
A1  - Grossart, Hans-Peter
T1  - Paradox reconsidered: Methane oversaturation in well-oxygenated lake waters
JF  - Limnology and oceanography
N2  - The widely reported paradox of methane oversaturation in oxygenated water challenges the prevailing paradigm that microbial methanogenesis only occurs under anoxic conditions. Using a combination of field sampling, incubation experiments, and modeling, we show that the recurring mid-water methane peak in Lake Stechlin, northeast Germany, was not dependent on methane input from the littoral zone or bottom sediment or on the presence of known micro-anoxic zones. The methane peak repeatedly overlapped with oxygen oversaturation in the seasonal thermocline. Incubation experiments and isotope analysis indicated active methane production, which was likely linked to photosynthesis and/or nitrogen fixation within the oxygenated water, whereas lessening of methane oxidation by light allowed accumulation of methane in the oxygen-rich upper layer. Estimated methane efflux from the surface water was up to 5 mmol m(-2) d(-1). Mid-water methane oversaturation was also observed in nine other lakes that collectively showed a strongly negative gradient of methane concentration within 0-20% dissolved oxygen (DO) in the bottom water, and a positive gradient within >= 20% DO in the upper water column. Further investigation into the responsible organisms and biochemical pathways will help improve our understanding of the global methane cycle.
Y1  - 2014
U6  - https://doi.org/10.4319/lo.2014.59.1.0275
SN  - 0024-3590
SN  - 1939-5590
VL  - 59
IS  - 1
SP  - 275
EP  - 284
PB  - Wiley
CY  - Waco
ER  -