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

How bioavailable iron was retained in surface waters and/or within the biota?

Boyd et al., 2000, Nature Inside the patchOutside the patch

SOIREE : In-situ artificial Fe fertilisation

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Fe demand

Fe supply

d=1-3 d=5 d=12-13Bowie et al., 2001, Deep Sea Res. I

Importance of Fe recycling

Abraham et al., 2000, Nature

Fe speciation

Fe bioavailability

Diatom - Copepod

55FeThalassiosira 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. l’Helguen (UMR 7127, Roscoff), G. Slawyk (LOB, Marseille)

55Fe/32Si13C/15N

55Fe Gross

Ingestion

After Vincent (2002)

55Fediss

Excretion / Dissolution

Experimental method - Principle

55Fepart

55Fediss

Sloppy feeding FP Dissolution

Fecal pellet production

55FeFP

55Fedis

s

55Fediss

Excretion

55Feeggs

Eggs production

Assimilation

55FecopNet Producti

on

Analytical development for Fe speciation

55DFe

55Fe(II)

55Fe(III)

55Fe-L

various types of resins (8-HQ, C18)various pHvarious Fe ligands

FeL (DFOB)Fe (III) + Fe (II)

C18

MeOH FeL(Fe-DFOB)

SW pH 3 Fe (II) +

Fe(III)

Copepods

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Fe

Temora longicornisCalanus helgolandicus

Fecal pellets + eggs

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Temora longicornisCalanus helgolandicus

Particulate Fe

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Temora longicornisCalanus helgolandicus

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Organic DFeInorganic-DFe

Temora longicornisCalanus helgolandicus

Dissolved Fe

Evolution of Fe in different compartments

19% 21% 22% 39%

51% 7% 17% 25%

Temora longicornis

Calanus helgolandicus

55Fe Gross

Ingestion

After Vincent (2002)

Excretion / Dissolution

Relative impact of regeneration processes

Sloppy feeding FP Dissolution

Fecal pellet production

55FeFP

Excretion

55Feeggs

Eggs production

Assimilation

55FecopNet Producti

on

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 55Fe, same experiments to study the effect on porphyrine concentrations and DMS/DMSP and other biogenic gases

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