Description: During research cruise AL595 (31.5. - 20.6.2023) onboard research vessel ALKOR, investigations were carried out at the Grimsey Hydrothermal Field offshore Northern Iceland as part of the Helmholtz InnoPool project “High CO2 – metabolic responses and bioeconomic opportunities”. For the first time, the Hover-AUVs Anton and Luise were successfully operated at water depths of up to 400m, which is close to the maximum operational depth of 500m specified for these Girona 500 AUVs. AUV Anton was used to measure high resolution multibeam data with a horizontal resolution of approximately 40cm cov- ering a total area of ca. 1.4km2. AUV Luise acquired five photo-mosaics with sub-centimeter resolution covering a total area of ca. 5.000m2. In addition, both AUVs carried CTD probes, which will allow to investigate the local distribution of hydrothermal activity. Both high-resolution bathymetry and pho- togrammetry data yield new insights into the morphology and overall structure of the vent site and its surrounding, which will be valuable for the interpretation of geophysical data previously acquired in the working area. Sampling with a multicorer (three successful deployments), a 300cm long gravity corer (five successful deployments), a BIGO lander (two successful deployments) and casts with the CTD- rosette (seven deployments) generated fluid, pore-fluid and sediment samples to be analyzed by the working groups Geomicrobiology and Biogeochemistry, Marine Natural Products and Marine Geochem- istry at GEOMAR and at Matís (Iceland, Natural Products only). Lab work to be carried out in the home labs will yield insights into the physiological adaptation of microbial communities and individual microbes to very high CO2 concentrations and will explore microbial utilization of CO2 for establishing CO2-based bioeconomic value chains.