Description: This cruise was conducted as part of the educational training of fishers in the framework of the transdisciplinary SeaRanger program which is scientifically accompanied by the Institute of marine ecosystem and fisheries Science (IMF) at the University of Hamburg (UHAM), the Christian-Albrechts University Kiel, Centre for Ocean and Society (CeOS), the Thuenen-Institute for Baltic Sea fisheries (TI-OF), and the German Centre for Integrative Biodiversity Research (iDiv) in the framework of the joint project SpaCeParti (Coastal Fishery, Biodiversity, Spatial Use and Climate Change: A Participative Approach to navigate the Western Baltic Sea into a Sustainable Future; Grant no. 03F0914) funded by the BMBF. In order to give the fishermen as realistic an application of the standard monitoring techniques as possible, the trip was planned in such a way that the training part was integrated into a scientific monitoring programme focussing on the spawning activity of fish in the Belt Sea. By sampling a standardised station grid contributing to the joint long-term sampling efforts in the Western Baltic Sea which are internationally coordinated by the WBCF (Western Baltic cod Forum), the fishers learned how plankton, fish and water samples are taken, preserved, and analysed and gained a comprehensive insight into the hydrography and fauna of the western Baltic. Similar to the previous cruise AL606 in January 2024 conducted by the IMF no cod larvae and generally less larvae compared to previous years were observed in the Bongo 500 μm net samples from the Plankton grid stations, potentially indicating a delayed spawning activity of fish in the Belt Sea potentially related to the comparably low water temperatures in winter 2023/24.

Description: MARIA S. MERIAN Cruise MSM106 was conceptualized as a joint research and curricular education cruise. The training component of MSM106 was part of the curriculum of the international Master program "Climate Change and Marine Sciences", which is currently being implemented at Universiade Técnica do Atlãntico (UTA) in Cabo Verde within the framework of the BMBF-funded WASCAL program ("West African Science Service Centre on Climate Change and Adapted Land Use"). Students from 12 West African countries participated in this cruise. Several modules of the curriculum were taught theoretically and practically at sea. Throughout the cruise West African students got involved in the different research components of MSM106. First, a mooring and an autonomous surface vehicle equipped with novel instrumentation for pCO 2 analysis got deployed at Nola Seamount near the Cabo Verdean Island Santo Antao to carry out a 3-month long test deployment. After ADCP and hydroacoustic biomass surveys near the archipelago an anticyclonic mode-water eddy near CVOO was investigated intensively (incl. CTD section, biogeochemical & ecological samplings). A full time-series sampling was conducted at CVOO as well. After this, daily stations along the transit towards Germany were carried out. Off Canary Islands the ESTOC time-series site was sampled, followed by another eddy survey off Portugal main land. The daily station scheme was continued along the transit to Bremerhaven. Off the Rhine River delta an extended sampling for microplastics has been conducted.

Description: Expedition SO294 served two scientific projects. The main program was designated towards the project CLOCKS: “Northern Cascadia: Extent of locked zone, prism deformation, slip-to-toe, and the edge of subduction”. The Cascadia subduction zone extending from northern California to the northern tip of Vancouver Island, remains unbroken by a megathrust earthquake since January 26, 1700, which is known from Tsunami records in Japan. The megathrust fault on the subducting Juan de Fuca (JdF) Plate is believed to be fully locked based on previous studies. We address several open questions on the state of locking of the megathrust by long-term monitoring experiments: nine short-period ocean bottom seismometers (OBS) were deployed combined with six ocean bottom pressure (OBP) gauges and six broad-band seismometers (deployed in a small sub-grid) allowing analyses of very low-frequency earthquakes and tremors. A set of eleven short- period OBS were deployed north of the Nootka Fault zone separating the JdF and Explorer Plates. The deeper structure of the subducting JdF Plate and the overlying North American plate was the target of an amphibious Magnetotelluric (MT) experiment. Along a 2D profile from the deformation front to the shelf off Vancouver Island, marine MT data were recorded for a month. A landward extension of the profile across Vancouver Island was recorded by the University of Alberta in the summer of 2022. These data are being jointly analyzed to identify and quantify hydration and dehydration processes, which play a major role in controlling seismicity. In order to image faulting and identify potential slip-to-toe events where the megathrust may have ruptured all the way to the deformation front, we acquired seismic data across the fragmented deformation front at the central northern Cascadia margin. Seismic data were also collected in the Winona Basin (Explorer Plate) to address the extent of subduction off northern Vancouver Island. These experiments were complemented by acquisition of heat-probe data measuring heat-flux. This will improve the thermal model used to define the limits of the locked zone by estimating the 125°C (upper limit) and 350°C (lower limit) isotherms. To study the recurrence rate of megathrust earthquakes on the Explorer Plate, we collected twelve cores at four slope failures. A secondary user project was added to SO294 to utilize the opportunity provided by the vessel operating off the West Coast of Canada. This project is a collaborative study between GEOMAR and Ocean Networks Canada (ONC) on potential CO2 storage in marine basalt complexes called CASCADIA CO2 (CCO2). ONC leads a project that aims at CO2 capture from the atmosphere and injection into oceanic crust in the Cascadia Basin, where boreholes from previous scientific drilling campaigns provided prior information on the physical properties of the basalt formations and overlying sediments. CCO2 studies the lateral variations of the basalt and its physical properties by the acquisition of seismic data on OBS optimized for the measurement of S-waves, a dataset yet missing in the assessments of the CO2 storage potential of basalt. In total, 22 OBS were deployed along two perpendicular profiles receiving seismic signals from the G-Gun array. Projects CLOCKS and CCO2 are accompanied by a mitigation program to protect marine mammals and other endangered species. Eight observers conducted continuous visual observations during daylight hours and 24h passive acoustic monitoring (PAM) during all seismic acquisition. An Infra-Red camera system was tested as identification tool for the presence of marine mammals.

Description: The research cruise M187 with the RV METEOR sailed January 25 th to March 4 th 2023 from Walvis Bay to Walvis Bay (Namibia), with a focus on investigating the biogeochemical gradients that exist between the Benguela Upwelling zone and the South Atlantic Subtropical Gyre. In order to achieve this, the two specific foci of the research cruise were to (i) track upwelling filaments as they advect offshore and interact with the subtropical gyre, and (ii) perform a high-resolution transect from upwelling sites to the subtropical gyre. On the research cruise, two filaments were successfully mapped from cold water upwelling sites near or over the Namibian shelf through to warmer waters offshore. This was followed by a transect of twelve stations outwards into the subtropical gyre, reaching a maximum westward position of 5 °W. Sampling stations were conducted to a maximum depth of 1000 m and involved an array of deployments to investigate the biogeochemistry of the water column. Further nutrient addition bioassay experiments were conducted throughout the research cruise to assess the nutrients (co-)limiting to phytoplankton growth. Collectively our research will shed light on key mechanisms establishing the major oceanic biogeochemical gradients between upwelling and subtropical gyre regions, so that they can be included in models used to predict the impacts of climate change.

Description: 5 – 25 July 2023, Kiel (Germany) – Tallinn (Estonia) – Kiel (Germany) CYANO-OC

Description: The main goal of cruise MSM61 was to install an autonomous multidisciplinary observatory at the summit of Senghor Seamount off the Cape Verdean archipelago. A suite of different mobile and moored instrument platforms equipped with physical, biological and biogeochemical instruments was deployed during the cruise in order to investigate spatio-temporal variability of physical and biogeochemical conditions and how these affect the local ecosystem at this openocean seamount. The research program further included hydrographic work, biological and biogeochemical sampling as well as video transects in the meso- and bathypelagic zones both at Senghor Seamount and at the Cape Verde Ocean Observatory (CVOO).

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.

Description: April 16 – May 13, 2023 Walvis Bay (Namibia) – Walvis Bay (Namibia) BANINO

Description: The research cruise M182 (MOSES Eddy-III) concludes a trilogy of research cruises conducted in the frame of the Helmholtz Association's Modular Observation Solutions for Earth Systems (MOSES) infrastructure, aiming at a comprehensive multi- and interdisciplinary study of ocean eddies in the northern tropical Atlantic. As an integral part of the BMBF-funded project "Role of eddies in the carbon pump of eastern upwelling systems - Demonstration Case Canary Current System" (REEBUS), launched in 2019, this study focuses on investigating the multi- layered influence of eddies on the lateral transport of biogeochemical properties and the carbon pump within deep-sea ecosystems. Ocean eddies have a significant impact on the physical, biogeochemical and biological aspects of coastal upwelling regions. Given the profound socio- economic impact of coastal upwelling areas, REEBUS takes a multidisciplinary approach to investigate the influence of ocean eddies on these systems. This expedition is motivated by the objective of acquiring novel insights into the functional dynamics of eddies, specifically elucidating their role in the CO2 source and sink functions inherent to eastern boundary upwelling systems. Furthermore, our investigative efforts encompassed a thorough examination of the biological carbon pump within both the designated upwelling areas and their associated oligotrophic regions. The synthesis of data from all REEBUS cruises, coupled with the inclusion of data from prior expeditions (MOSES Eddy-I and II) within this geographical region, promises to yield a high scientific potential.