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Seasonal total methane depletion in limestone caves

Journal Article


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Abstract


  • Methane concentration in caves is commonly much lower than the external atmosphere, yet the cave CH 4 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 CH 4 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 CH 4 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 CH 4 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.

Authors


  •   Waring, Chris (external author)
  •   Hankin, S (external author)
  •   Griffith, David W. T.
  •   Kertesz, Michael (external author)
  •   Kobylski, Victoria (external author)
  •   Wilson, Neil (external author)
  •   Coleman, Nicholas (external author)
  •   Kettlewell, Graham C. (external author)
  •   Zlot, Robert (external author)
  •   Bosse, Michael (external author)
  •   Bell, Graham (external author)

Publication Date


  • 2017

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), 8314-1-8314-12.

Scopus Eid


  • 2-s2.0-85027499731

Ro Full-text Url


  • http://ro.uow.edu.au/cgi/viewcontent.cgi?article=5992&context=smhpapers

Ro Metadata Url


  • http://ro.uow.edu.au/smhpapers/4942

Start Page


  • 8314-1

End Page


  • 8314-12

Volume


  • 7

Issue


  • 1

Place Of Publication


  • United Kingdom

Abstract


  • Methane concentration in caves is commonly much lower than the external atmosphere, yet the cave CH 4 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 CH 4 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 CH 4 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 CH 4 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.

Authors


  •   Waring, Chris (external author)
  •   Hankin, S (external author)
  •   Griffith, David W. T.
  •   Kertesz, Michael (external author)
  •   Kobylski, Victoria (external author)
  •   Wilson, Neil (external author)
  •   Coleman, Nicholas (external author)
  •   Kettlewell, Graham C. (external author)
  •   Zlot, Robert (external author)
  •   Bosse, Michael (external author)
  •   Bell, Graham (external author)

Publication Date


  • 2017

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), 8314-1-8314-12.

Scopus Eid


  • 2-s2.0-85027499731

Ro Full-text Url


  • http://ro.uow.edu.au/cgi/viewcontent.cgi?article=5992&context=smhpapers

Ro Metadata Url


  • http://ro.uow.edu.au/smhpapers/4942

Start Page


  • 8314-1

End Page


  • 8314-12

Volume


  • 7

Issue


  • 1

Place Of Publication


  • United Kingdom