Compte-rendu opérationnel de la campagne Momarsat 2022. Zone de travail - Lucky Strike infrastructure de recherche– EMSO-Açores Navire Pourquoi Pas ? Submersible Nautile

The MoMARSAT cruise series ensures the annual maintenance of the EMSO-Azores observatory on the Lucky Strike vent field. This seabed observatory has been operating since 2010 and aims to acquire long time-series data (>10 years) on hydrothermal, tectonic, volcanic processes and the associated ecosystems of an active hydrothermal field located on the Mid-Atlantic Ridge. EMSO-Azores is part of the European network EMSO ERIC (European Multidisciplinary Seafloor and water column Observatory), supported in France by the Research Infrastructure (MESR) EMSO-FR whose management is ensured by a collaboration Ifremer-CNRS. The array includes an observatory infrastructure that comprises a surface buoy (BOREL) ensuring the transfer of data by satellite to a server on land. Two junction boxes (SEAMON) deployed on the bottom communicate acoustically with BOREL and through a cable to the connected instruments. In its current configuration (after MOMARSAT 2022 maintenance), the "connected" part of the observatory includes a surface weather station, a seismometer (OBS), a bottom pressure gauge, a biological observation module (TEMPO- with an HDTV camera and 2 projectors), an oxygen sensor and a turbidity sensor, a fluid sampler (DEAFS), an EMSO generic instrumentation module (EGIM) and four hydrophones (HYDROCTOPUS). The infrastructure also includes autonomous instruments that store their data internally: 4 OBSs, 2 pressure sensors placed on the bottom, 28 autonomous temperature probes deployed within smokers and on diffusion zones, 6 autonomous current meters placed on the bottom, 6 microbiological colonisers, 8 biological colonizers, 3 autonomous cameras (POMMEs); and an oceanographic mooring. These "unconnected" elements contribute to extend the spatial coverage of the area studied during each maintenance cruise. Maintenance operations include the replacement of the BOREL-SEAMON infrastructure and the connected instruments, their reconditioning on board and their redeployment. In situ sampling of rocks, fluids, fauna, microorganisms and the acquisition of imaging transects on targeted sites allow the multi-year monitoring of the system and complete the infrastructure data. These measurements are also used to calibrate/validate the measurements made by the instrumental fleet. This year, bottom operations was carried out by the manned submersible Nautile. In order to optimize ship time, a physical oceanography program to study the hydrodynamic circulation on this part of the ridge was implemented during nights (project MicroRiYo@Sea 3D). The coordination of maintenance operations and the initial data exploitation are handled by Mathilde Cannat (EMSO France manager) and Pierre Marie Sarradin (EMSO-Azores Regional team leader). The management of on-board operations is coordinated this year by Marjolaine Matabos, Pierre-Marie Sarradin and Laurent Gautier. The data acquired during the Momarsat cruises are available on the portal EMSO-Azores. The study area is part of Portugal's EEZ and is also a ¿Marine Protected Area¿ (OSPAR).