Plattform Platform	Reise-Nr. Cruise-No.	Zeitraum Period	Projekt Project	Arbeitsgebiet Working area
Alkor	AL553	15.04.2021 - 24.04.2021		Mecklenburg Bight Baltic Sea Kiel Bight Bornholm Basin

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

Ziel der Reise / Objectives of Cruise:

Physical, chemical, biological research and fishery oceanography This multidisciplinary cruise extended a 35-year long-term data series on ecosystem composition and functioning of the pelagic systems of the Baltic Sea. A key characteristic of the cruise is the integration of oceanographic and biological information to enhance understanding to enhance the causal understanding of changes in the structure and function of food webs and the population structure and biological characteristics of fish stocks, as well as 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 of AL553 lay on the Bornholm Basin as most important spawning area of Baltic cod, but also included additional sampling in the Western Baltic Sea. 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 dietary tracer, nutritional condition and genetic analyses), and pelagic fishery hauls. The latter served to determine stock structure, gonadal maturation and liver parasite infestation of cod, and to sample tissue and otolith samples for individual-level genetic and ecological analyses. The abundance and distribution of fishes in the cruise area was also assessed with hydroacoustic methods. Additional cruise components were: (i) cod gonad sampling for fecundity studies, (ii) vertically resolved phytoplankton and zooplankton sampling for studies of plankton phenology, (iii) sampling of pelagic fishes and plankton commmunities for eDNA assessments, (iv) sampling of marine viruses.

Messungen / Measurements