title: Deconstructing Methane Emissions from a Small Northern European River: Hydrodynamics and Temperature as Key Drivers.
abstract: Methane (CH4) emissions from small rivers and streams, particularly via ebullition, are currently under-represented in the literature. Here, we quantify the methane effluxes and drivers in a small, Northern European river. Methane fluxes are comparable to those from tropical aquatic systems, with average emissions of 320 mg CH4m-2d-1. Two important drivers of methane flux variations were identified in the studied system: 1) temperature-driven sediment methane ebullition and 2) flow-dependent contribution suspected to be hydraulic exchange with adjacent wetlands and small side-bays. This flow-dependent contribution to river methane loading is shown to be negligible for flows less than 4 m3s-1and greater than 50% as flows exceed 7 m3s-1. While the temperature-ebullition relationship is comparable to other systems, the flow rate dependency has not been previously demonstrated. In general, we found that about 80% of the total emissions were due to methane bubbles. Applying ebullition rates to global estimates for fluvial systems, which currently are not considered, could dramatically increase emission rates to ranges from lakes or wetlands. This work illustrates that small rivers can emit significant methane and highlights the need for further studies on the link between hydrodynamics and connected wetlands.
authors.affiliation: Aquatic Physics, Department F.-A. Forel, Section of Earth and Environment Sciences, Faculty of Science, University of Geneva , CH-1211 Geneva 4, Switzerland.|Chemical Analytics and Biogeochemistry, Leibniz-Institute of Freshwater Ecology and Inland Fisheries (IGB) , 12587 Berlin, Germany.|GEOMAR Helmholtz Centre for Ocean Research Kiel, RD2 Marine Biogeochemistry, 24148 Kiel, Germany.
authors.forename: Daniel F
authors.initials: DF
authors.lastname: McGinnis
authors.affiliation: Scripps Institution of Oceanography, La Jolla, California 92093, United States.
authors.forename: Nicole
authors.initials: N
authors.lastname: Bilsley
authors.affiliation: GEOMAR Helmholtz Centre for Ocean Research Kiel, RD2 Marine Biogeochemistry, 24148 Kiel, Germany.
authors.forename: Mark
authors.initials: M
authors.lastname: Schmidt
authors.affiliation: GEOMAR Helmholtz Centre for Ocean Research Kiel, RD2 Marine Biogeochemistry, 24148 Kiel, Germany.|Kongsberg Maritime Contros GmbH, 24148 Kiel, Germany.
authors.forename: Peer
authors.initials: P
authors.lastname: Fietzek
authors.affiliation: Chemical Analytics and Biogeochemistry, Leibniz-Institute of Freshwater Ecology and Inland Fisheries (IGB) , 12587 Berlin, Germany.|Institute of Biology, Freie Universität Berlin , 14195 Berlin, Germany.
authors.forename: Pascal
authors.initials: P
authors.lastname: Bodmer
authors.affiliation: Chemical Analytics and Biogeochemistry, Leibniz-Institute of Freshwater Ecology and Inland Fisheries (IGB) , 12587 Berlin, Germany.
authors.forename: Katrin
authors.initials: K
authors.lastname: Premke
authors.affiliation: Institute for Environmental Sciences, Environmental Physics, University of Koblenz-Landau , 76829 Landau, Germany.
authors.forename: Andreas
authors.initials: A
authors.lastname: Lorke
authors.affiliation: Chemical Analytics and Biogeochemistry, Leibniz-Institute of Freshwater Ecology and Inland Fisheries (IGB) , 12587 Berlin, Germany.
authors.forename: Sabine
authors.initials: S
authors.lastname: Flury
mesh_terms: D057446:Hydrodynamics; D060106:Lakes; D008697:Methane; D045483:Rivers; D013696:Temperature
chemical_list: D008697:Methane