Chlorophyll and other indicators of productivity in the Eastern Weddell Gyre between 0°E and 23°E - Preliminary Results of Polarstern Expedition ANT XX/2, Synpart projectWalter Geibert (1), Regina Usbeck (1), (2), Jill Schwarz (1), Claudia Hanfland (1), Adrian Webb (3) and Isabelle Ansorge (3)(1) Alfred Wegener Institute for Polar and Marine Research, Bremerhaven, Germany(2) Now Fa. Fielax, Company for Scientific Data Management, Bremerhaven, Germany(3) University of Cape Town, Dept. of Oceanography, Cape Town, South AfricaAuthor to whom correspondence should be addressed: wgeibert@awi-bremerhaven.deThe Weddell Gyre, extending from the Antarctic Peninsula to about 35°E, is one of the most dynamic regions with respect to the vertical exchange of heat, salt, and nutrients. Deep upwelling supplies large amounts of nutrients to the surface, which results in a large potential productivity, but the region south of the Polar Front is commonly described as a HNLC (High Nutrient, Low Chlorophyll) region, which is partly supported by satellite derived surface chlorophyll values and sediment accumulation rate data. Although the western part of the Weddell Gyre, the Weddell Sea, is relatively well described, there is a lack of data from the Eastern Weddell Gyre. Data from nearby areas as well as results from inverse modelling (Usbeck et al. 2002) point to unexpectedly high export of biogenic silica from the surface waters to intermediate depths. The Synpart project (Synoptical investigation of particle flux in the Eastern Weddell Gyre) was initiated in order to get a comprehensive impression of particle flux in this region. Therefore, the Synpart project comprises SeaWiFS satellite data of chlorophyll a, the measurement of vertical chlorophyll profiles, nutrient and oxygen data, and determination of Thorium export from the surface layer. In the near future, accumulation rates on sediment surface samples taken during ANT XX/2 will be determined via 230Th. Here we present preliminary results of the expedition that give an impression on one of the poorest known regions of the Southern Ocean.