Seasonal total methane depletion in limestone caves
Loading...
Date
2017-08-16
Journal Title
Journal ISSN
Volume Title
Publisher
Springer Nature
Abstract
Methane concentration in caves is commonly much lower than the external atmosphere, yet the cave CH4 depletion causal mechanism is contested and dynamic links to external diurnal and seasonal temperature cycles unknown. Here, we report a continuous 3-year record of cave methane and other trace gases in Jenolan Caves, Australia which shows a seasonal cycle of extreme CH4 depletion, from ambient ~1,775 ppb to near zero during summer and to ~800 ppb in winter. Methanotrophic bacteria, some newly-discovered, rapidly consume methane on cave surfaces and in external karst soils with lifetimes in the cave of a few hours. Extreme bacterial selection due to the absence of alternate carbon sources for growth in the cave environment has resulted in an extremely high proportion 2–12% of methanotrophs in the total bacteria present. Unexpected seasonal bias in our cave CH4 depletion record is explained by a three-step process involving methanotrophy in aerobic karst soil above the cave, summer transport of soil-gas into the cave through epikarst, followed by further cave CH4 depletion. Disentangling cause and effect of cave gas variations by tracing sources and sinks has identified seasonal speleothem growth bias, with implied palaeo-climate record bias. © 2017, The Author(s)
Description
Open Access. This article is licensed under a Creative Commons Attribution 4.0 International License. Author correction is attached - article has been updated to reflect the correction.
Keywords
Seasons, Methane, Limestone, Caves, Atmospheric chemistry, Geochemistry, Biogeochemistry
Citation
Waring, C. L., Hankin, S. I., Griffith, D. W. T., Kertesz, M. A., Kobylski, V., Wilson, N. L., Coleman, N. V., Kettlewell, G., Zlot, R., Bosse, M. & Bell, G. (2017). Seasonal total methane depletion in limestone caves. Scientific reports, 7(1), 1-12. doi:10.1038/s41598-017-07769-6