1. Iron : Chemistry, sources and sinks.

2.  Iron is the limiting factor in the surface water of S.O.  HNLC conditions « Iron hypothesis » (Martin et al. 1990) (Petit et al. 1990)  Enhanced iron supply during glacial time  increase in productivity  This explains drawdown of atmospheric CO 2 during glacial times.

3.  Phytoplankton in the Antarctic deplete silicic acid Si(OH) 4 to a far greater extent than they do nitrate NO 3 -. (Pondaven et al. 2002)  This pattern can be reverse by the addition of iron which dramatically lower Si(OH) 4 :NO 3 - uptake ratios. Higher iron supply during glacial time would thus drive the Antarctic toward NO 3 - depletion with excess Si(OH) 4 remaining in surface waters. A switch from Si(OH) 4 to NO 3 - depletion in the glacial Southern Ocean

4. Winter mixing Upwelling Vertical diffusion Atmospheric « New Iron » in present Southern Ocean: Open ocean Kerguelen plateau ? ?

5. Continental margins are an important source of iron: Chlorophyll (mg m -3 ) Southern Ocean : Blain et al. 2000 St 28 St 19 St 27 Atlantic ocean Laes et al. GRL (2003).

6. Fe(III) ’ Fe(OH) 2 + Fe(OH) 3 Fe(OH) 4 - 0.1 nm 1 nm10 nm0.1 µm1 µm10 µm100 µm Soluble Fe Dissolved Fe Colloidal Fe Particulate Fe Fe Humic Fe Colloid Fe(II) ’ Fe 2+ FeCO 3 Alumino-silicate clays intracellular and extracellular Detritus FeL Iron distribution and speciation : 3 size fractions + Fe(II)/fe(III)+ ligands Iron chemistry :

7. IRON TEAM: Water Column : international team. LEMAR, LOB, NIOZ and ARC long experience in iron work have already work together at sea SAFE cruise in October 2004. On the Marion Dufresne: sampling and onboard analysis. To collect samples for other trace metal determination To provide clean seawater for OBEX Sediment : LGE and LSCE

8. Atmosphere : LOV and LISA  To determine the particles abundance of the area  To determine the size distribution in order to attempt a IRON FLUX calculation.  To determine the mineralogical composition.  To determine some geochemical tracers (Al, Pb, …) and elements of biogeochemical interest such as Fe and P.  To quantify dissolved iron originating from these particles in the surface seawater IRON TEAM:

9. Front tower Small front tower Meteo-platform the front tower seems the most appropriate place: feasibility? But more sophisticated