Plattform Platform	Reise-Nr. Cruise-No.	Zeitraum Period	Projekt Project	Arbeitsgebiet Working area
Poseidon	POS476_477	17.10.2014 - 24.10.2014		Baltic Sea Gotland Basin

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

Ziel der Reise / Objectives of Cruise:

The combined cruises Poseidon 476-77 are follow up cruises of ALKOR 422 which was carried out in Latvian waters in 2013 in the same working area. Our general investigations focus on redox-dependent nutrient, nitrogen and trace metal cycles in the benthic boundary layer of the suboxic to anoxic eastern Gotland Basin. We aim to study release rates and inventories of phosphate and iron under varying degrees of bottom water oxygenation and to quantify source/sink mechanisms of the benthic boundary layer for nitrogen species and trace metals under changing oxygen conditions to assess potential feedbacks on upper mixed layer processes. While Alkor 422 was carried out in summer we wanted to study the changing of oxygen conditions in fall and winter. The natural gradient of bacterial mats (Beggiatoa ssp.), which are indicators of the suboxic zone were investigated during the expedition by studying various stations from anoxic to anoxic water (autumn situation). Two instruments were employed for our investigation the towed video/still-camera system OFOS (Ocan Floor Observation System) and a TV-controlled CTD/Rosette water sampler. Two small bottom observatories were deployed at 96m and 123m for nine months to monitor changes in: CTD, turbidity, chlorophyll, oxygen and currents during the winter and spring situation. The observatories will be retrieved in July 2015 with R/V Poseidon.

Messungen / Measurements

Verankerungen / Moorings