7 January 2012 - 11 March 2012, Cape Town – Punta Arenas

The cruise leg ANT-XXVIII/3 starts in Cape Town on 7 January 2012 and ends in Punta Arenas on 11 March 2012. During the cruise two research projects will be carried out:

1. “Eddy pump“, an interdisciplinary study of the physical, chemical and biological processes driving the carbon pumps in the Southern Ocean, in particular within the numerous embedded mesoscale eddies.

2. SYSTCO II (SYSTem COupling in the deep Southern Ocean II), a study on a) diversity, distribution and abundance of deep-sea organisms in relation to surface water productivity and sedimentation of organic material to the seafloor; b) ecology of deep-sea fauna, and c) DNA preservation in the water column and the deep-sea sediments and its possible use to study the eukaryotes diversity in the present and the past.

Both research projects complement each other and thus sampling will take place at numerous joint stations along the cruise track. A focus will be on studies in several mesoscale eddies, chosen to cover various oceanographic and biogeochemical/biogeographical regimes, especially:

(1) The region with enhanced eddy kinetic energy in the area south of 50°S at approx. 30°E, associated with a southward veering of the Polar Front at the eastern extent of the Weddell Gyre, which despite presumed enhanced iron supply from upwelling is assumed to be dominated by the diatom Fragilariopsis kerguelensis.

(2) The central Antarctic Circumpolar Current along the Polar Front at 0°E marked by transient phytoplankton blooms, presumably driven by pulses of iron supply through mesoscale upwelling events associated with a low to moderate level of eddy kinetic energy (EKE), and alternating between Chaetoceros and F. kerguelensis dominance.

(3) The `Chaetoceros Province’ in the wake of South Georgia and the Antarctic Peninsula marked by high long-term mean sea surface chlorophyll concentration, presumably fostered by lateral advection of iron from the shelf or by iron released from melting icebergs). En route between the main investigation sites, conventional hydrographic and biogeochemical station work will be performed, in particular across Drake Passage which features a strong south-north gradient of EKE but overall very low sea surface chlorophyll.