The EPONTA program (biological oceanography) deals with the biogeochemistry of land fast ice in the vicinity of Dumont d'Urville, particularly with regard to the sympagic community on the ice underside and the platelet layer. Past cruises have revealed a high productivity of this community as well as complex nutrient regime. Preliminary data on the sedimentation rate revealed a strong particle flux from the fast ice long before the ice breaks up. The 2007 program will corroborate this information and we also intend to improve primary and secondary production measurements as well as particle flux estimates over a spatial and temporal gradient.

For a better understanding of the relationships between the sympagic biota and the polar environment, we propose to study during the cruise 2007-2008:

1) the Primary production on ice, using Micro-electrodes O2 (Micro-Optodes; Mock et al., 2002) and to relate this to the under ice irradiance levels using quantameter
2) obtain an estimate of the secondary production (macrozooplankton), by pumping and filtering the platelet ice and water under ice and obtaining images using a small mini ROV. This is expected to provide semi quantitative information on consumers such as krill and amphipods
3) the particulate flux along a northern transect of several km, using 4 sediment traps (Hydro-Bios-MST6) regularly spaced and positioned 5 m under the ice. This experiment will provide additional information on sedimentation (grazing packaging or in mass sedimentation) and the coast-to-offshore land mass effect or gradient
4) in order to evaluate the inter-annual variability, some biogeochemical measurements will be done on sea ice (major nutrients, Chloropigments, pH, alkalinity, S°/°°) as well as taxonomy and appropriate additional investigations such as calcium carbonate precipitation, ice thickness measurements etc.