Full-scale evaluation of methane production under oxic conditions in a mesotrophic lake.
basic_science · Level V
Where this comes from
- Record sourced from PubMed, PMID 29162809.
- Also identified by DOI 10.1038/s41467-017-01648-4 and PMC identifier 5698424.
- Licence recorded as CC BY.
- The licence permits redistribution, so the abstract is shown in full and the full text is available from the publisher.
Abstract
Oxic lake surface waters are frequently oversaturated with methane (CH<sub>4</sub>). The contribution to the global CH<sub>4</sub> cycle is significant, thus leading to an increasing number of studies and stimulating debates. Here we show, using a mass balance, on a temperate, mesotrophic lake, that ~90% of CH<sub>4</sub> emissions to the atmosphere is due to CH<sub>4</sub> produced within the oxic surface mixed layer (SML) during the stratified period, while the often observed CH<sub>4</sub> maximum at the thermocline represents only a physically driven accumulation. Negligible surface CH<sub>4</sub> oxidation suggests that the produced 110 ± 60 nmol CH<sub>4</sub> L<sup>-1</sup> d<sup>-1</sup> efficiently escapes to the atmosphere. Stable carbon isotope ratios indicate that CH<sub>4</sub> in the SML is distinct from sedimentary CH<sub>4</sub> production, suggesting alternative pathways and precursors. Our approach reveals CH<sub>4</sub> production in the epilimnion that is currently overlooked, and that research on possible mechanisms behind the methane paradox should additionally focus on the lake surface layer.