keops meeting, 2-3 march 2005, marseille obex 2: role of grazing on fe chemistry obj. 3.2.3:...
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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
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
0
2
4
6
8
10
12
Fe
flu
xe
s (
pM
d-1
)
1 2 3
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
0
4000
8000
12000
16000
20000
0 5 10 15 20 25
Time (h)
dp
m 55
Fe
Temora longicornisCalanus helgolandicus
Fecal pellets + eggs
0
10000
20000
30000
40000
50000
60000
0 5 10 15 20 25
Time (h)
dp
m 55
Fe
Temora longicornisCalanus helgolandicus
Particulate Fe
0
50000
100000
150000
200000
0 5 10 15 20 25
Time (h)
dp
m 55
Fe
Temora longicornisCalanus helgolandicus
0
4000
8000
12000
16000
20000
0 5 10 15 20 25
Time (h)
dp
m 55
Fe
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
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