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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. KEOPS meeting, 2-3 March 2005, Marseille. SOIREE : In-situ artificial Fe fertilisation. Inside the patch. Boyd et al., 2000, Nature. Outside the patch. Importance of Fe recycling.

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KEOPS meeting, 2-3 March 2005, Marseille

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

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

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

  4. Experimental method - Principle 55Fediss 55Fediss 55Fepart 55Fediss 55Feeggs 55Fecop Fecal pellet production 55FeFP Net Production Assimilation Sloppy feeding Excretion FP Dissolution Eggs production 55Fediss 55Fe Gross Ingestion Excretion / Dissolution After Vincent (2002)

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

  6. Evolution of Fe in different compartments Copepods Particulate Fe Fecal pellets + eggs 20000 200000 60000 Temora longicornis Temora longicornis Calanus helgolandicus Calanus helgolandicus Temora longicornis 16000 50000 150000 Calanus helgolandicus Fe Fe 40000 12000 Fe 55 55 100000 55 dpm dpm 30000 dpm 8000 Temora longicornis 20000 50000 Calanus helgolandicus 4000 10000 0 0 0 0 5 10 15 20 25 0 5 10 15 20 25 0 5 10 15 20 25 Time (h) Time (h) Time (h) Dissolved Fe 20000 Organic DFe Inorganic-DFe 16000 Fe 12000 55 dpm 8000 4000 0 0 5 10 15 20 25 Time (h)

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

  8. II- To extend grazing experiments to microzooplankton community => dilution experiments, isolation of microzooplankton species 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 at least once at Kerguelen Plateau and once in the POOZ What do we plan to do during KEOPS? I- To apply grazing experiments to natural phyto- and mesozoo-plankton communities III- Without addition of 55Fe, 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 2- Mesozooplankton grazing experiments: net towing (200 µm-500 µm) 3- “Clean” radioactive container (laminar flow hood) 4- Access to the trace-metal clean container (cleaning and preparation) 5- A place with binocular for zooplankton sorting (in situ temperature) 6- Liquid scintillation counter 7- Deck-Incubators

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