Second IFM-GEOMAR-HYPOX expedition to the eastern Gotland Basin (R/V ALKOR, leg AL-355)

From 29. May to 21. June R/V ALKOR is working in the eastern Gotland Basin in the central Baltic Sea. A major focus of the cruise, led by Dr. Olaf Pfannkuche from HYPOX partner IFM-GEOMAR, is to understand the role of open sea sediments of the Baltic Proper as sources and sinks for nitrogen, phosphorus, trace metals and carbon under low oxic to anoxic conditions. A lot of the work will be dedicated to in situ measurements of turnover and fluxes of nitrogen compounds, phosphate, iron, manganese and carbon in the benthic boundary layer at variable bottom water oxygen concentrations. In parallel to these measurements under natural conditions, the effects of variable oxygen availability in the bottom water on N-speciation and release of nutrients will be determined by in situ experiments. Further activities during the cruise comprise biological investigations (meiobenthos, epibenthos) and sea floor imaging. A lander observatory will be deployed at 97m for three weeks to measure currents and oxygen variability near the bottom and to take time lapse photos of the activity of bottom organisms. Major working sites will be in the eastern Gotland Basin of the Baltic Proper along a depth transect line in the Latvian EEZ. The transect line includes stations , which have been visited during a pre-study with R/V Poseidon (POS-369, July/August 2008) and during the first HYPOX Cruise with R/V Alkor (AL-346, Sept/Oct. 2009). These stations, ranging from shallow water (~ 60 m) to deepest part of the basin (~250 m), are representative for the Gotland Basin and include sites with both oxygenated and anoxic/sulfidic bottom water.


Fig. 1: R/V ALKOR: Tonnage 1322GT, Length 54,5m, Beam 12,5m, Scientific Crew 12. (Photo: IFM-GEOMAR)


Fig. 2: Map of ALKOR cruise No. 355: working area framed. (O. Pfannkuche, IFM-GEOMAR).


Fig. 3: Deployment of a GEOMAR-Lander from R/V ALKOR (Photo O. Pfannkuche, IFM-GEOMAR)

Text: Olaf Pfannkuche, IFM-GEOMAR