https://doi.org/10.5194/bg-2021-167 Preprint. Discussion started: 23 June 2021 c Author(s) 2021. CC BY 4.0 License. Hydrogen and carbon isotope fractionation factors of aerobic methane oxidation in deep-sea water Shinsuke Kawagucci1 2, Yohei Matsui3 4, Akiko Makabe1, Tatsuhiro Fukuba5, Yuji Onishi1 6, Takuro Nunoura7, Taichi Yokokawa1 5 1 Super-cutting-edge Grand and Advanced Research (SUGAR) Program, Institute for Extra-cutting-edge Science and Technology Avant-garde Research (X-star), Japan Agency for Marine-Earth Science and Technology (JAMSTEC), Yokosuka 237-0061, Japan 2 Institute of Geochemistry and Petrology, ETH Zürich, Zürich 8092, Switzerland 3 Advanced Science-Technology Research (ASTER) Program, X-star, JAMSTEC, Yokosuka 237-0061, Japan 10 4 Department of Engineering Mechanics and Energy, University of Tsukuba, Tsukuba 305-0006, Japan 5 Institute for Marine-Earth Exploration and Engineering (MarE3), JAMSTEC, Yokosuka 237-0061, Japan 6 The Center for Ecological Research, Kyoto University, Otsu 520-2113, Japan 7 Research Institute for Marine Resources Utilization (MRU), JAMSTEC, Yokosuka 237-0061, Japan Correspondence to: Shinsuke Kawagucci (
[email protected]) 15 & Taichi Yokokawa (
[email protected]) Abstract. (248 words) Isotope fractionation factors associated with various biogeochemical processes are important in ensuring the practicality of isotope tracers in biogeosciences at large. Methane is a key component of the subsurface biosphere and a notable greenhouse gas, making the accurate evaluation of methane cycles, including microbial 20 methanotrophy, imperative. Although the isotope fractionation factors associated with methanotrophy been examined under various conditions, the dual-isotope fractionation factors of aerobic methanotrophy in oxic seawater column remain unclear.