1. KEOPS meeting, 2-3 March 2005, Marseille OBEX 2: Role of grazing on Fe chemistry Obj. 3.2.3: Feedback of biological activity on Fe speciation

2. How bioavailable iron was retained in surface waters and/or within the biota? Boyd et al., 2000, Nature Inside the patch Outside the patch SOIREE : In-situ artificial Fe fertilisation Bowie et al., 2001, Deep Sea Res. I Importance of Fe recycling Abraham et al., 2000, Nature Fe speciation Fe bioavailability

3. Diatom - Copepod 55 Fe Thalassiosira weissflogii, ~ 10 µm Temora longicornis, ~ 1 mm Calanus helgolandicus, ~ 2.5 mm 24h Fecal pellets ~ 200 µm LEMAR : G. Sarthou, M. Gallinari, O. Ragueneau, A. Leynaert, M. Barreau Collaborations : D. Vincent (MREN, Wimereux), S. lHelguen (UMR 7127, Roscoff), G. Slawyk (LOB, Marseille) 55 Fe/ 32 Si 13 C/ 15 N

4. 55 Fe Gross Ingestion After Vincent (2002) 55 Fe diss Excretion / Dissolution Experimental method - Principle 55 Fe part 55 Fe diss Sloppy feeding FP Dissolution Fecal pellet production 55 Fe FP 55 Fe diss Excretion 55 Fe eggs Eggs production Assimilation 55 Fe cop Net Production

5. Analytical development for Fe speciation 55 DFe 55 Fe(II) 55 Fe(III) 55 Fe-L various types of resins (8-HQ, C18) various pH various Fe ligands FeL (DFOB) Fe (III) + Fe (II) C18 MeOH FeL (Fe-DFOB) SW pH 3 Fe (II) + Fe(III)

6. Copepods 0 4000 8000 12000 16000 20000 0510152025 Time (h) dpm 55 Fe Temora longicornis Calanus helgolandicus Fecal pellets + eggs 0 10000 20000 30000 40000 50000 60000 0510152025 Time (h) dpm 55 Fe Temora longicornis Calanus helgolandicus Particulate Fe 0 50000 100000 150000 200000 0510152025 Time (h) dpm 55 Fe Temora longicornis Calanus helgolandicus Evolution of Fe in different compartments

7. 19% 21%22%39% 51%7%17%25% Temora longicornis Calanus helgolandicus 55 Fe Gross Ingestion After Vincent (2002) Excretion / Dissolution Relative impact of regeneration processes Sloppy feeding FP Dissolution Fecal pellet production 55 Fe FP Excretion 55 Fe eggs Eggs production Assimilation 55 Fe cop Net Production

8. What do we plan to do during KEOPS? I- To apply grazing experiments to natural phyto- and mesozoo-plankton communities II- To extend grazing experiments to microzooplankton community => dilution experiments, isolation of microzooplankton species at least once at Kerguelen Plateau and once in the POOZ IV- To extend experiments to bacterial degradation/solar irradiance (OBEX3) and to viral lysis (OBEX4) => radiolabelled bacteria with and without viruses => radiolabelled phytoplankton with and without viruses III- Without addition of 55 Fe, same experiments to study the effect on porphyrine concentrations and DMS/DMSP and other biogenic gases

9. What do we need during KEOPS? 1- Clean seawater (Go-Flo): ~ 40 L / experiment various size-fractionations: 0.02-0.2-0.8-2-20-200-500 µm 3- Clean radioactive container (laminar flow hood) 2- Mesozooplankton grazing experiments: net towing (200 µm-500 µm) 7- Deck-Incubators 5- A place with binocular for zooplankton sorting (in situ temperature) 4- Access to the trace-metal clean container (cleaning and preparation) 6- Liquid scintillation counter