Document Type
Article
Department/Program
Virginia Institute of Marine Science
Publication Date
2014
Journal
Limnology And Oceanography
Volume
59
Issue
1
First Page
275
Last Page
284
Abstract
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.
DOI
10.4319/lo.2014.59.1.0275
Keywords
Carbon-Isotope Fractionation; Methanosarcina-Barkeri; Fresh-Water; Methanogenesis; Emissions; Hydrogen; Oxidation; Acetate; Column; Budget
Recommended Citation
Tang, KW; McGinnis, DF; Frindte, K; Bruchert, V; and Grossart, HP, Paradox reconsidered: Methane oversaturation in well-oxygenated lake waters (2014). Limnology And Oceanography, 59(1), 275-284.
10.4319/lo.2014.59.1.0275
