The Momarsat cruise was held from August 4th to August 24th 2024 on the R/V L’Atalante with the ROV VIctor6000 with Pierre-Marie Sarradin & Marjolaine Matabos as chief scientists. The main objective of the Momarsat series of cruises is the maintenance of the EMSO-Azores observatory. In its actual configuration, the infrastructure is composed of two Sea Monitoring Nodes (SEAMON). The first, SEAMON west, dedicated to large-scale geophysical studies, is moored in the center of the fossil lava lake. This node hosts an Ocean Bottom Seismometer (OBS), a pressure gauge (JPP) and a generic environmental measurement module (EGIM). The EGIM is equipped with a CTD, an optode, a turbidimeter, a hydrophone and an ADCP. The second, SEAMON east, is deployed at the base of the Eiffel Tower active edifice to study the links between faunal dynamics and physico-chemical factors. It is composed of an Aanderaa optode and a Wetlab turbidimeter. An ecological observatory module equipped with a HD video camera and two LED lights is located 10 meters away from the edifice. An array of four Ocean Bottom Hydrophones (Hydroctopus) is deployed south of the active edifice. The two SEAMON nodes and associated sensors were successfully recovered and redeployed.
The MoMARSAT experimental design also includes the recovery and/or deployment of autonomous instruments: 4 OBS, 7 autonomous current meters and a temperature probe array (29 autonomous probes deployed in smokers and diffusing areas), a sequential fluid sampler (DEAFS), 3 small autonomous video cameras, 10 biological and microbiological colonization devices. Site studies, including video surveys, sampling and monitoring of long-term colonization/perturbation experiments, were also performed during the cruises. The two pressure gauges (JPP) were retrieved this year for maintenance and replacement of their stands that were corroded. In situ sampling of rocks, fluids, fauna, microorganisms and the acquisition of imaging transects on targeted sites allow the multi-year monitoring of the ecosystem and complete the infrastructure data. These measurements are also used to calibrate/validate the measurements made by the instrumental array. This year, imagery surveys were conducted to map geological and biological features as well as scientific gears and dead weights at the vent field scale. These maps will be shared with the Azoreans government to inform marine protected area management (PROTECT project).
Therefore, the cruise was a real success! All objectives were fulfilled through 10 dives totaling over 230 hours of bottom time. A FB web page was dedicated to the cruise (https://www.facebook.com/CampagneMomarsat/).