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 similar to 1,775 ppb to near zero during summer and to similar 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.
Original language | English |
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Article number | 8314 |
Pages (from-to) | 1-12 |
Number of pages | 12 |
Journal | Scientific Reports |
Volume | 7 |
DOIs | |
Publication status | Published - 16 Aug 2017 |
Externally published | Yes |
Bibliographical note
Copyright the Author(s) 2017. Version archived for private and non-commercial use with the permission of the author/s and according to publisher conditions. For further rights please contact the publisher.Correction: Waring, C.L., Hankin, S.I., Griffith, D.W.T. et al. Author Correction: Seasonal total methane depletion in limestone caves. Sci Rep 8, 6059 (2018). https://doi.org/10.1038/s41598-018-23872-8