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: Poseidon cruise 518 (leg 1 and 2) took place in the framework of the Horizon 2020 project STEMM-CCS of the EU. The project’s main goal is to develop and test strategies and technologies for the monitoring of subseafloor CO2 storage operations. In this context a small research-scale CO2 gas release experiment is planned for 2019 in the vicinity of the Goldeneye platform located in the British EEZ (central North Sea). Cruise POS518 aimed at collecting necessary oceanographic and biogeochemical baseline data for this release experiment. During Leg 1 ROV PHOCA was used to deploy MPI’s tool for high-precision measurements of O2, CO2 and pH in the bottom water at Goldeneye. In addition, ROV push cores and gravity cores were collected in the area for sediment biogeochemical analyses, and video-CTD casts were conducted to study the water column chemistry. The stereo-camera system and a horizontally looking multibeam echosounder, both, for determining gas bubble emissions at the seafloor were deployed at the Figge Maar blowout crater in the German Bight. Investigations were complemented by hydroacoustic surveys detecting gas bubble leakages at several abandoned wells in the North Sea as well as the Figge Maar. Surface water alkalinity as well as CH4, CO2, and water partial pressures in the air above the sea surface were measured continuously during the cruise. During Leg 2 three different benthic lander systems were deployed to obtain baseline data of oceanographic and biogeochemical parameters for a small research-scale CO2 gas release experiment planned for 2019. The first lander was equipped with an acoustic Doppler current profiler (ADCP), a CTD and an O2 optode. It was deployed for 6 days close to Goldeneye to obtain high resolution data which can be linked to the long-term measurements of the NOC-Lander. This lander is equipped with a suite of sensors to monitor temperature, conductivity, pressure, current speed and direction, hydro-acoustic, pH, pCO2, O2 and nutrients over a period of about 10 months with popup telemetry units for data transmission via IRIDIUM satellite telemetry every 3 months. Two short-term deployments of the Biogeochemical Observatory (BIGO) were conducted to study the molar ratio between oxygen and CO2-fluxes at the seafloor. Sediment cores obtained by gravity and multi corer were collected for sediment biogeochemical analyses and video-CTD casts were used to study the chemistry of the water column.

Description: Integrated Ocean Drilling Program Expedition 320/321, "Pacific Equatorial Age Transect" (Sites U1331–U1338), was designed to recover a continuous Cenozoic record of the equatorial Pacific by coring above the paleoposition of the Equator at successive crustal ages on the Pacific plate. These sediments record the evolution of the equatorial climate system throughout the Cenozoic. As we gained more information about the past movement of plates and when in Earth's history "critical" climate events took place, it became possible to drill an age transect ("flow-line") along the position of the paleoequator in the Pacific, targeting important time slices where the sedimentary archive allows us to reconstruct past climatic and tectonic conditions. The Pacific Equatorial Age Transect (PEAT) program cored eight sites from the sediment surface to basement, with basalt aged between 53 and 18 Ma, covering the time period following maximum Cenozoic warmth, through initial major glaciations, to today. The PEAT program allows the reconstruction of extreme changes of the calcium carbonate compensation depth (CCD) across major geological boundaries during the last 53 m.y. A very shallow CCD during most of the Paleogene makes it difficult to obtain well-preserved carbonate sediments during these stratigraphic intervals, but Expedition 320 recovered a unique sedimentary biogenic sediment archive for time periods just after the Paleocene/Eocene boundary event, the Eocene cooling, the Eocene–Oligocene transition, the "one cold pole" Oligocene, the Oligocene–Miocene transition, and the middle Miocene cooling. Expedition 321, the second part of the PEAT program, recovered sediments from the time period roughly from 25 Ma forward, including sediments crossing the Oligocene/Miocene boundary and two major Neogene equatorial Pacific sediment sections. Together with older Deep Sea Drilling Project and Ocean Drilling Program drilling in the equatorial Pacific, we can delineate the position of the paleoequator and variations in sediment thickness from ~150°W to 110°W longitude.

Description: Cruise SO210 with RV SONNE to the active continental margin off Chile was conducted by shiptime exchange with RV METEOR. Funds for mobilizing the research team were provided by the German Science Foundation (DFG) in conjunction with the Collaborative Research Centre (SFB) 574 of the University of Kiel. In the first years, the SFB 574 investigated the pathways and fluxes of volatiles through the erosive subduction zone off Central America. For comparison, the studies were extended to the accretionary margin off Central Chile. Cruise SO210 is the last cruise conducted in the framework of SFB 574 and based on investigations of previous SFB-cruises on the RVs VIDAL GORMAZ and JAMES COOK. The first leg of cruise SO210 was dedicated to long gravity coring for volcanic ash layers from the erruptive Southern Volcanic Zone (SVZ) of the Andes that were either deposited as fallouts onto the incoming Nazca Plate or transported down the slope and across the Chile Trench. Eight gravity cores of 12 m length were retrieved seaward of the Chile Channel on the outer rise of the Nazca Plate. The second goal for coring was the description and dating of previously mapped submarine landslides as well as retrieval of slide-related material for geo-technical experiments. As the deployment frame for long coring had to be removed on the second leg we continued coring for mass-wasting and geochemistry with short cores. Ten gravity cores of 3 or 6 m barrel length were retrieved upslope of slides, the glide plane and redeposited material downslope of the slide evacuation area. This sampling activity was supported by detailed acoustic surveys with Parasound and multibeam to remap critical areas for mass wasting in search for events, e.g. triggered by the recent Mw 8.8 Maule Earthquake, such as flanks of submarine canyons or previously detected submarine slides and to fill data gaps in the existing bathymetric data. The major activity of the entire cruise was dedicated to the search and detailed sampling of manifestations of fluid discharge activity on the Chilean forearc. A total of 11 deployments with the video sled OFOS and 12 dives by the ROV KIEL 6000 were conducted for ground-truthing of information which indicated possible seep activity and has been obtained during previous cruises to the Chilean forearc. In five working areas we found manifestations of fluid discharge. In these areas the survey was followed by an intense sampling of bottom water, sediments, carbonates, mega and meiofauna and the deployment of instrumentation on the seafloor. The goal of these deployments was to measure in situ seabed methane emission rates and associated fluxes of sulfide and major electron acceptors such as oxygen at seep sites along the Chilean margin and to understand its controls. This was accompanied by CTD casts to trace oxygen and the fate of methane discharge in the water column. Sediment cores obtained by multicorer or ROV were used for the geochemical characterization of the pore water and microbiological studies which include turnover rate measurements, molecular studies, flow through experiments and sampling of active sediments. Authigenic carbonates obtained by TV-Grab or ROV were sampled for fauna, biomarker studies and investigations to reconstruct the growth structures, calcification processes and fluid-pathway systematic. The sampling of sediments and carbonates recovered a unique fauna with 79 different taxa, several of them appear to be species new to science.

Description: The AL561 cruise was conducted in the framework of the project APOC (“Anthropogenic impacts on Particulate Organic Carbon cycling in the North Sea”). This collaborative project between GEOMAR, AWI, HEREON, UHH, and BUND is to understand how particulate organic carbon (POC) cycling contributes to carbon sequestration in the North Sea and how this ecosystem service is compromised and interlinked with global change and a range of human pressures include fisheries (pelagic fisheries, bottom trawling), resource extraction (sand mining), sediment management (dredging and disposal of dredged sediments) and eutrophication. The main aim of the sampling activity during AL561 cruise was to recover undisturbed sediment from high accumulation sites in the Skagerrak/Kattegat and to subsample sediment/porewater at high resolution in order to investigate sedimentation transport processes, origin of sediment/POC and mineralization processes over the last 100- 200 years. Moreover, the actual processes of sedimentation and POC degradation in the water column and benthic layer will be addressed by sampling with CTD and Lander devices. In total 9 hydroacoustic surveys (59 profiles), 4 Gravity Corer, 7 Multicorer, 3 Lander and 4 CTD stations were successfully conducted during the AL561 cruise.

Description: In the marine environment elevated electrical conductivities may be caused by sulfide mineralizations within the seafloor as well as hot saline pore fluids. Such conductive targets may be studied with suitable electromagnetic systems like the novel coil-system MARTEMIS1, which we previously used to investigate a known zone of sediment covered mineralization at the Palinuro Seamount (cruises POS483 & POS509) and in the vicinity of the TAG hydrothermal mound at the Mid Atlantic Ridge (cruise JC138). Both the Palinuro site as well as the sites in the vicinity of the TAG hydrothermal mound (Shinkai, Double Mound, MIR) are hydrothermally inactive and, thus, allowed to study, how the responses of an inductive EM system is influenced and shaped by mineralizations within the seafloor without having to consider the effect of of heated pore fluids. In the interpretation of the collected data at these inactive sites we learned that the MARTEMIS system is able to detect conductivity anomalies in the vicinity of mineralizations. (...)

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.