Plattform Platform	Reise-Nr. Cruise-No.	Zeitraum Period	Projekt Project	Arbeitsgebiet Working area
Alkor	AL522	15.05.2019 - 30.05.2019		Arkona Basin Mecklenburg Bight Gdansk Bight Baltic Sea Gotland Basin Kiel Bight Bornholm Basin

Fahrtleiter Chief Scientist	Institut Institute	Auslaufhafen Port of departure	Einlaufhafen Port of return	Stationskarte Station map	Schiffsroute Trackchart
Reusch Thorsten	Helmholtz Centre for Ocean Research Kiel (GEOMAR)	Kiel	Kiel

Ziel der Reise / Objectives of Cruise:

Physical, chemical, biological research and fishery oceanography The AL522 cruise extended a long-term data series on (eco-)system composition and functioning of the Baltic Sea, with a focus on the deeper basins. The series has been collected in similar form since 1986. A key characteristic of the cruise is the integration of oceanographic and biological information to enhance understanding of environmental and (fish) population fluctuations, and evolutionary processes in this system. The resulting data- and sample sets support ongoing projects in the Research Unit Marine Evolutionary Ecology at GEOMAR, as well as the EU Horizon 2020 project GoJelly and several international collaborations. The spatial focus lay on the Bornholm Basin as most important spawning area of Baltic cod, but also included the Western Baltic Sea, Arkona and Gotland Basin, Gdansk Deep, and Stolpe Trench. Specific investigations included a detailed hydrological survey (oxygen, salinity, temperature) of the cruise area, plankton surveys (zoo- and ichthyplankton including gelatinous plankton, with the goal to determine the composition and the abundance and vertical and horizontal distribution of species, and to take samples for later measurements of nutritional condition), and pelagic fishery hauls. The latter served to determine stock structure, gonadal maturation, stomach contents, and egg production of sprat and cod, and to sample tissue and otolith samples for individual-level genetic and ecological analyses of cod. The abundance and distribution of fishes in the cruise area was also assessed with hydroacoustic methods. Additional cruise components were: (i) cod gonad and liver sampling for fecundity + parasite studies, (ii) vertically resolved plankton sampling for studies of plankton phenology (iii) depth-resolved sampling of microplastic using an neuston sledge (iv) sampling and experimental work of photosynthesis rates of different phytoplankton fractions (v) eDNA filter sampling to compare with traditional net based methods.

Messungen / Measurements