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Abyssal plain communities rely on the overlying water column for a settling flux of organic matter. The origin and rate of this flux as well as the controls on its fine-scale spatial distribution following seafloor settlement are largely unquantified. This is particularly true across regions where anthropogenically-induced seafloor disturbance has occurred. Here, we observed, quantified and mapped a mass deposition event of gelatinous zooplankton carcasses (pyrosomes) in July-September 2015 across one such physically disturbed region in the Peru Basin polymetallic nodule province (4150 m). Seafloor in this area was disturbed with a plough harrow in 1989 (as part of the DISCOL experiment) causing troughs in the sediment. Other parts were disturbed with an epibenthic sled (EBS) during a cruise in 2015 resulting in steep-walled, U-shaped troughs. We investigated two hypotheses: a) gelatinous food falls contribute significantly to the abyssal plain carbon pump and b) physical seafloor disturbance influences abyssal distribution of organic matter. We combined optical and bathymetric seafloor observations, to analyze pyrosome distribution on seabeds with different levels of disturbance. 2954 pyrosome colonies and associated taxa were detected in > 14,000 seafloor images. The mean regional carbon (C) deposition associated with pyrosome carcasses was significant compared to the flux of particulate organic C (182 to 1543%), and the total respired benthic C flux in the DISCOL Experimental Area (39 to 184%). EBS-disturbed seafloor tracks contained 72 times more pyrosome-associated C than an undisturbed reference site, and up to 4 times more than an area disturbed in 1989. Deposited pyrosomes collected had a higher proportion of labile fatty acids compared to the sediment. We document the temporal and spatial extent of an abyssal food fall event with unprecedented detail and show that physical seafloor disturbance results in the accumulation of detrital material. Such accumulation may reduce oxygen availability and alter benthic community structure. Understanding both the relevance of large food falls and the fine scale topography of the seafloor, is necessary for impact assessment of technologies altering seafloor integrity (e.g. as a result of bottom-trawling or deep seabed mining) and may improve their management on a global scale.

ALKOR cruise AL583 took place as part of the EMFF (European Maritime and Fisheries Fund)‐funded projects BASTA (Boost Applied munition detection through Smart data detection in and AI workflows; https://www.basta‐munition.eu) and ExPloTect (Ex‐situ, near‐real‐time detection compound detection in seawater) (also EMFF‐funded). It was the continuation of the munition monitoring started within the BMBF‐funded project UDEMM (Environmental Monitoring for the Delaboration of Munition in the Sea; https://udemm.geomar.de/) and is already part of the new project CONMAR (https://conmar‐ munition.eu/) as part of the DAM mission sustainMare (https://www.sustainmare.de/). Additional sampling supported chemical analysis method development within the MarTERA project AMMOTRACe (Marine AMMunitiOn dump site exploration by surface‐ and underwater‐based laser mass spectrometric TRACing technology; https://www.geomar.de/en/ammotrace ). The original plan was to first work for one week in the North Sea and have a crew change after one week in Kiel and continue working in the Baltic Sea. This plan changed; ALKOR worked instead in Baltic Sea in support of for the Federal Public Prosecutor General and the Federal Police during the first week. The change of crew happened on 18th October in Kiel and the original Baltic Sea cruise was conducted as planned.

17. - 31.03.2023

ALKOR cruise AL567 took place as part of the EMFF (European Maritime and Fisheries Fund)‐funded project BASTA (Boost Applied munition detection through Smart data 3etection3n and AI workflows; https://www.basta‐munition.eu) and ExPloTect (Ex‐situ, near‐real‐time 3etection compound 3etection in seawater) (also EMFF‐funded). It was the continuation of the munition monitoring started within the BMBF‐ funded project UDEMM (Environmental Monitoring for the Delaboration of Munition in the Sea; https://udemm.geomar.de/). In previous cruises (POS530 MineMoni I in 2018 and AL548 MineMoni II in 2020) data was gathered for a broad baseline study in the German Baltic Sea. Within UDEMM, expertise was developed to detect, exactly locate and monitor munition (e.g. torpedoes, sea mines, ground mines) on the seafloor using optical and hydroacoustic means. In addition, chemical analyses of dissolved contaminants in the water and sediments was performed. Results indicate a moderate contamination level on regional and coastal scale, but proof higher levels of explosive‐type compounds for specific local areas. Data acquired during this cruise are used in BASTA for the development of AUV‐based and AI‐supported munition detection. On the other hand, the project ExPloTect (Ex‐situ, near‐real‐time exPlosive compound deTection in seawater) (also EMFF‐funded) addresses the need for a more effective quasi in‐situ sampling approach to detect explosive compounds in seawater on board of a ship. A prototype system was used and successfully tested for the first time during this cruise. The main focus of the cruise was placed onto the already known dumpsites Kolberger Heide and Lübeck Bight, Falshöft (Schleswig‐Holstein) and Trollegrund (Mecklenbu rg‐Vorpommern). In each area high‐ resolution multibeam mapping was performed and contact lists, indicating potential munition objects, were produced right after acquisition on board. Based on that data, AUV surveys were conducted to ground‐truth possible contacts via detailed photograph and magnetometer mapping. This was complemented with towed video profiles, SubBottom Profiler (VLIZ Institute) and towed gradiometer surveys (g‐tec SA). The transits to and between those sites were planned along former constraint routes during WWII. These routes were main targets of the British Air Force and mines and bombs can be expected along these ways. During transits water samples were taken with on a CTD‐ (conductivity, temperature, depth) rosette‐mounted Niskin bottles in regular distances, in order to obtain a comprehensive understanding of munition compounds (inter alia trinitrotoluene (TNT)) measurements across the German Baltic Sea. The cruise was supported by the 3rd Minensuchgeschwader vessel ‘Bad Rappenau’. During 2 days, work was performed in cooperation between the research vessel ALKOR and the naval unit with their AUV REMUS 100 conducting high resolution sidescan surveys over several pre‐defined targets. In addition, navy divers recovered mussel moorings for the toxicological institute of the UKSH. The pre‐planned identification of munition objects via navy divers did unfortunately fail due to low visibility conditions.

This open access book presents the results of three years collaboration between earth scientists and data scientists, in developing and applying data science methods for scientific discovery. The book will be highly beneficial for other researchers at senior and graduate level, interested in applying visual data exploration, computational approaches and scientifc workflows.

Kampfmittel im Meer stellen aufgrund des von ihnen ausgehenden Risikos für die Bevölkerung und die bereits eintretende Belastung der Umwelt eine enorme Herausforderung dar. Von besonderer Bedeutung sind hierbei Belastungsschwerpunkte wie das Versenkungsgebiet Kolberger Heide. Dieser Beitrag beschreibt mögliche Maßnahmen, um mit solchen Belastungsschwerpunkten umzugehen. Hierzu gehören die Einrichtung von Sperrgebieten, die Etablierung eines Monitoring-Programms, die Durchführung historischer Recherchen sowie technischer Erkundungsarbeiten, die Räumung von Kampfmitteln und an die Öffentlichkeit gerichtete Informationskampagnen. Anschließend wird untersucht, wie diese Maßnahmen bislang in der Kolberger Heide Anwendung finden. Zuletzt werden mögliche zukünftige Maßnahmen vorgeschlagen.

31.05. - 10.07.2022, Mindelo - Pt. Delgada

31.05. - 10.07.2022, Mindelo - Pt. Delgada

The abyssal seafloor in the Clarion-Clipperton Zone (CCZ) in the NE Pacific hosts the largest abundance of polymetallic nodules in the deep sea and is being targeted as an area for potential deep-sea mining. During nodule mining, seafloor sediment will be brought into suspension by mining equipment, resulting in the formation of sediment plumes, which will affect benthic and pelagic life not naturally adapted to any major sediment transport and deposition events. To improve our understanding of sediment plume dispersion and to support the development of plume dispersion models in this specific deep-sea area, we conducted a small-scale, 12-hour disturbance experiment in the German exploration contract area in the CCZ using a chain dredge. Sediment plume dispersion and deposition was monitored using an array of optical and acoustic turbidity sensors and current meters placed on platforms on the seafloor, and by visual inspection of the seafloor before and after dredge deployment. We found that seafloor imagery could be used to qualitatively visualise the redeposited sediment up to a distance of 100 m from the source, and that sensors recording optical and acoustic backscatter are sensitive and adequate tools to monitor the horizontal and vertical dispersion of the generated sediment plume. Optical backscatter signals could be converted into absolute mass concentration of suspended sediment to provide quantitative data on sediment dispersion. Vertical profiles of acoustic backscatter recorded by current profilers provided qualitative insight into the vertical extent of the sediment plume. Our monitoring setup proved to be very useful for the monitoring of this small-scale experiment and can be seen as an exemplary strategy for monitoring studies of future, upscaled mining trials. We recommend that such larger trials include the use of AUVs for repeated seafloor imaging and water column plume mapping (optical and acoustical), as well as the use of in-situ particle size sensors and/or particle cameras to better constrain the effect of suspended particle aggregation on optical and acoustic backscatter signals.

31.05. - 10.07.2022, Mindelo - Pt. Delgada 2. Wochenbericht 06. - 12.06.2022