Methanotroph activity and connectivity between two seep systems north off Svalbard Provisionally Accepted

Tim De Groot^1* Dimitri Kalenitchenko^{2, 3} Manuel Moser² Claudio Argentino² Giuliana Panieri² Matteus Lindgren² Benedicte Ferré² Mette M. Svenning² Helge Niemann^{1, 2, 4*}

• ¹Royal Netherlands Institute for Sea Research (NIOZ), Netherlands
• ²UiT The Arctic University of Norway, Norway
• ³UMR7266 Littoral, Environnement et Sociétés (LIENSs), France
• ⁴Utrecht University, Netherlands

Understanding methane flux dynamics in Arctic cold seep systems and the influence of oceanic currents on microbial methane-oxidizing bacteria (MOB) is crucial for assessing their impact on Arctic methane emissions. Here, we investigate methane dynamics and associated microbial communities at two cold seep areas, Norskebanken and Hinlopen Trough, North of Svalbard. Methane concentrations and methane oxidation rates (MOx) were measured in bottom and surface waters, with higher values observed in bottom waters, particularly at Hinlopen Trough. Dominant water column MOB clusters were Milano-WF1B-03 and Methyloprofundus. Methane availability drove MOx activity, as indicated by higher concentrations in bottom waters and sediments where MOx was elevated, too. Sediment MOB communities varied among locations, with Hinlopen featuring higher diversity and abundance. Similarities between sediments and water column MOBs suggests potential recruitment from sediments, possibly via a bubble shuttle mechanism. In addition, bottom water MOB community composition also showed similarities between the Norskebanken and Hinlopen seeps implying an exchange of water column microbes between the two seep areas, which may likely be driven by the regional current regime.