Mine Monitoring in the German Baltic Sea 2021; Dumped munition monitoring - AL567, 17th – 31st October 2021, Kiel (Germany) – Kiel (Germany), „MineMoni‐III 2021“

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