Plattform Platform	Reise-Nr. Cruise-No.	Zeitraum Period	Projekt Project	Arbeitsgebiet Working area
Alkor	AL458	03.06.2015 - 19.06.2015	SFB 754 B09	Baltic Sea Gulf of Riga

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

Ziel der Reise / Objectives of Cruise:

AL458 aimed at studying the production, composition and degradation of particulate and dissolved organic matter along natural gradients of inorganic nutrients, oxygen and seawater CO2 in the Baltic Sea. The cruise track crossed the Southern Baltic Proper, the deep Gotland Basin and the Gulf of Riga. Sampling of depth profiles along transects was combined with onboard experiments that investigated (i) effects of oxygen concentration and organic matter composition on the bacterial turnover of dissolved organic matter (ii) effects of labile organic matter and nutrients on microbial activities under oxic and anoxic conditions (iii) degradation of halocarbons by microbial communities. The standard station program included a CTD cast and water sampling at different depths for biological and chemical measurements, Apstein net hauls (20 ?m, 300 ?m) and light profiles. Wednesday, 3.6.: We left Kiel at 8:30 in stormy weather and head towards the southern Baltic Sea. After safety instructions, first test station in the Fehmarn Belt. Thursday, 4.6.: The HELCOM station BY2 in the Arkona Sea is our first regular station. BY4 is sampled in the afternoon. Surface samples are taken to start the first experiment on halocarbon decomposition. Friday, 5.6.: The station program is conducted at OMTF0212 and BMPK2. Net samples indicate the dominance of dinoflagellates in the size fraction <20 ?m. A large number of copepods is caught in the net sample >300?m. At both stations oxygen at depth (>60m) is strongly reduced but no anoxia detected. Saturday, 6.6.: We entered to Polish EEZ in the night and conduct the full station program at Pl-P3 and K1. Sunday, 7.6.: In addition to the station program on BY10, water is sampled for filling of the sediment trap tubes. The traps are prepared for deployment the following day. Monday, 8.6.: At the Gotland Deep: The drifting sediment trap was successfully deployed of. It will collect particles over a period of 48h at the depth of 40, 60, 110 and 180m. BY15 is sampled with 9 depths in the afternoon. Tuesday, 9.6.: Station program at BY 11 with a high resolution sampling profile (0, 10, 20, 30, 40, 60, 70, 80, 110, 130, 150 190m). Wednesday, 10.3.: Successful recovery of the sediment trap in the morning. Afterwards, start of POM decomposition experiments with trap material. We continued our cruise track and entered the Gulf of Riga (St. 142) in the afternoon. Thursday, 11.3.: We continued our station program at the Gulf of Riga at 119. Second halocarbon decomposition experiment with water from 119 started. Around noon a Lativian pilot came on board to navigate to Riga. At the entrance of the river Daugawa we did one CTD deployment to estimate the contribution of the river inflow on biogeochemistry of the Gulf of Riga. Friday, 12.6.: An international workshop on marine research and management is held at the Faculty of Biology, University of Latvia, Riga. In the afternoon a reception was given on Alkor for 28 registered Latvian scientists and two representatives of the German embassy. Saturday, 13.6.: We left Riga in the morning and continued our field program in the Gulf of Riga at station 119. During the day the first experiment on DOM decomposition ended and samples were filtered and preserved for a variety of chemical and biological analyses. In the afternoon, the regular station program was conducted at station Gulf of Riga 2. Sunday, 14.6.: The station program was conducted at BY21. In addition four CTD cast were conducted to collect oxic water from 40m and anoxic water from 110m depth. This water was used for preparation of the 2nd trap deployment the following days as well as to start the 2nd experiment on DOM decomposition. Monday 15.6.: The trap was deployed in the morning at the Landsort Deep. Afterwards, BY31 was sampled with high resolution. Tuesday, 16.6.: The trap was successfully recovered at 04:00 UTC. We then headed to stations OMTF0240 and BY36 to continue our station prog

Messungen / Measurements