title: Methane fluxes show consistent temperature dependence across microbial to ecosystem scales.
abstract: Methane (CH4) is an important greenhouse gas because it has 25 times the global warming potential of carbon dioxide (CO2) by mass over a century. Recent calculations suggest that atmospheric CH4 emissions have been responsible for approximately 20% of Earth's warming since pre-industrial times. Understanding how CH4 emissions from ecosystems will respond to expected increases in global temperature is therefore fundamental to predicting whether the carbon cycle will mitigate or accelerate climate change. Methanogenesis is the terminal step in the remineralization of organic matter and is carried out by strictly anaerobic Archaea. Like most other forms of metabolism, methanogenesis is temperature-dependent. However, it is not yet known how this physiological response combines with other biotic processes (for example, methanotrophy, substrate supply, microbial community composition) and abiotic processes (for example, water-table depth) to determine the temperature dependence of ecosystem-level CH4 emissions. It is also not known whether CH4 emissions at the ecosystem level have a fundamentally different temperature dependence than other key fluxes in the carbon cycle, such as photosynthesis and respiration. Here we use meta-analyses to show that seasonal variations in CH4 emissions from a wide range of ecosystems exhibit an average temperature dependence similar to that of CH4 production derived from pure cultures of methanogens and anaerobic microbial communities. This average temperature dependence (0.96 electron volts (eV)), which corresponds to a 57-fold increase between 0 and 30°C, is considerably higher than previously observed for respiration (approximately 0.65 eV) and photosynthesis (approximately 0.3 eV). As a result, we show that both the emission of CH4 and the ratio of CH4 to CO2 emissions increase markedly with seasonal increases in temperature. Our findings suggest that global warming may have a large impact on the relative contributions of CO2 and CH4 to total greenhouse gas emissions from aquatic ecosystems, terrestrial wetlands and rice paddies.
authors.affiliation: Environment and Sustainability Institute, University of Exeter, Penryn, Cornwall, TR10 9EZ. UK.
authors.forename: Gabriel
authors.initials: G
authors.lastname: Yvon-Durocher
authors.affiliation: Department of Biological Sciences, Macquarie University, Sydney, NSW 2109, Australia.
authors.forename: Andrew P
authors.initials: AP
authors.lastname: Allen
authors.affiliation: Department of Thematic Studies - Water and Environmental Studies, Linköping University, SE-581 83 Linköping, Sweden.
authors.forename: David
authors.initials: D
authors.lastname: Bastviken
authors.affiliation: Max-Planck-Institute for Terrestrial Microbiology, Karl-von-Frisch-Strasse 10, 35043 Marburg, Germany.
authors.forename: Ralf
authors.initials: R
authors.lastname: Conrad
authors.affiliation: 1] Department of Ecology and Environmental Sciences, Umeå University, Linnaeus väg 6, SE-901 87 Umeå, Sweden [2] Department of Ecology and Genetics, Limnology, Uppsala University, Norbyvägen 18D, SE-752 36, Uppsala Sweden [3] Department of Ecology and Evolutionary Biology, Princeton University, Princeton, 106A Guyot Hall, New Jersey 08544, USA.
authors.forename: Cristian
authors.initials: C
authors.lastname: Gudasz
authors.affiliation: Département des sciences biologiques, Université du Québec à Montréal, Montréal, Province of Québec, H2X 3X8, Canada.
authors.forename: Annick
authors.initials: A
authors.lastname: St-Pierre
authors.affiliation: Earth Systems Research Center, Institute for the Study of Earth, Oceans, and Space, University of New Hampshire, Durham, New Hampshire 03824, USA.
authors.forename: Nguyen
authors.initials: N
authors.lastname: Thanh-Duc
authors.affiliation: Département des sciences biologiques, Université du Québec à Montréal, Montréal, Province of Québec, H2X 3X8, Canada.
authors.forename: Paul A
authors.initials: PA
authors.lastname: del Giorgio
mesh_terms: D000693:Anaerobiosis; D059001:Aquatic Organisms / Q000378:metabolism; D001105:Archaea / Q000378:metabolism*; D001272:Atmosphere / Q000737:chemistry; D057486:Carbon Cycle; D002245:Carbon Dioxide / Q000032:analysis; D019069:Cell Respiration; D017753:Ecosystem; D019015:Geologic Sediments / Q000382:microbiology; D057232:Global Warming; D017752:Greenhouse Effect; D008697:Methane / Q000032:analysis / Q000378:metabolism*; D012275:Oryza / Q000378:metabolism; D010788:Photosynthesis; D012621:Seasons; D013696:Temperature; D053833:Wetlands
chemical_list: D002245:Carbon Dioxide; D008697:Methane