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S u r f a c e O c e a n

Primary production ( 14 C) and phosphate availability in the south Pacific ocean T. MOUTIN, P. RIMMELIN Laboratoire d ’Océanographie et de Biogéochimie Centre d ’Océanologie de Marseille. h n. CO 2. CO 2. POC. DOC. S u r f a c e O c e a n. Nutrients (N, P, Si, Fe). CO 2.

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S u r f a c e O c e a n

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  1. Primary production (14C) and phosphate availability in the south Pacific oceanT. MOUTIN, P. RIMMELINLaboratoire d ’Océanographie et de BiogéochimieCentre d ’Océanologie de Marseille

  2. hn CO2 CO2 POC DOC S u r f a c e O c e a n Nutrients (N, P, Si, Fe) CO2 Export production Biological pump : carbon transfert to the ocean interior by biological process CO2 : mineral carbon including carbonates POC : Particulate Organic Carbon DOC : Dissolved Organic Carbon Moutin, 2000 (Océanis)

  3. hn POC CO2 P Scientific objectives : To obtain reference measurements of primary production. To study phosphate availabilty, and its influence on planktonic community structure and on associated carbon fluxes.

  4. Primary production (JGOFS 14C method, 24-h of incubation duration) « Against » biological diversity, a « simple » method to compare phytoplankton productivity in the ocean Phytoplankton Productivity : Bangor, March 18th-22nd 2002

  5. Secondary objective concerning primary production : to validate the model established in the Mediterranean Sea for daily primary production rates (dawn-to-dawn) calculation. POMME cruises in the Eastern North Atlantic Ocean Phytoplankton Productivity : Bangor, March 18th-22nd 2002

  6. Meso-zooplankton Nano-micro phytoplankton DOC DOC export POC export Carbon flux Heterotrophic flagellates Micro- zooplankton Heterotrophic bacteria Pico- phytoplankton s u r f a c e o c e a n Si PO4 Regenerate production ------ +++++ New Production Conceptual scheme showing competitive absorbtion of phosphate by bacteria and phytoplankton and possible implications on the carbon cycle in a simple trophic chain model (Moutin 2000 from Thingstad et al., 1997 and Thingstad 1998). Phosphate flux

  7. Size fractionation (0.2, 0.6, 2 µm) Heterotrophic Bacteria Pico- phytoplankton Nano-micro phytoplankton PO4 Biomass (Particulate Phosphate, Chlorophylle a (who?), Bacterial Biomass ?) Carbon and phosphate uptakes 33P and 14C methods (Incubation duration << 24 h) Phosphate availabilty -Characteritics of the phosphacline (Concentration vs depth measurements by the classic and/or the MAGIC method (if PO4<100 nM)) -Turnover times measurements (=>Indirectly estimated orthophosphate concentration) -Dissolved Organic Phosphate concentration (labile DOP at surface only) Planktonic production (C & P) To study phosphate availabilty, and its influence on planktonic community structure.

  8. Primary production (JGOFS 14C method 24-h) Planktonik production (C & P) One profile each day number 2 for « three days » stations Needs : Radio-isotopes container CTD one hour before dawn 2.5 liters per depth (max 12 depth) in situ One profile each « one day » station Needs : 3 meters of working lab outside of the RA container CTD two hours before solar noon 4.5 liters per depth (max 9 depths) Deck incubators

  9. ? CHENAL BIOSOPE ALOHA : 2 d CHENAL : 4 h Lowest orthohosphate turnover time measured Comparison between ALOHA and Chenal des Loyauté Station (DIAPALIS Cruises) Van Den Broeck et al., MEPS, in press. P-limitation N-limitation Absence de Trichodesmium Présence de Trichodesmium SRP D. Karl et al., Nature 1997. Time ALOHA D. Karl JGOFS Conference ”Ocean Biogeochemistry: A New Paradigm”. 13-17 April 2000. Bergen Image composite Seawifs

  10. Collaborations : -Frede Thingstad : -to study the phosphate cycle in the upper photic zone of oligotrophic ocean. -France Van Wambeke : -to study bacterial production vs primary production and the role of heterotrophic bacteria in the DOP pool utilization. -Dave Karl : (in discussion) -to compare phosphate availabilities in the South and the North Pacific gyres (ALOHA station).

  11. PROSOPE Cruise « Expected » results ! Ionnian Sea Gibraltar Moutin, Thingstad, Van Wambeke, Marie, Slawyk, Raimbault & Claustre, 2002 (Limnol. Oceanogr.)

  12. 1 month 1 week 1 day 2.5 h Turnover times

  13. 1000.0 ENAO Apr 2001 100.0 ) ENAO Sep 2001 nM ] ( 10.0 4 [PO 1:1 1.0 0.1 0.1 1.0 10.0 100.0 1000.0 SRP ( nM ) { Océan Atllantique Nord Est 4 Mer Méditerranée 3 Pi (nM) déduites de T 2 1 Pi (nM) déduites de T 0 1 2 3 4 5 6 M IO Stations SRP (nM) Proposition d ’une méthode indirecte simple (Radio isotopique 33P) pour évaluer indirectement la concentration en orthophosphate (L.D. < 0.02 nM). Moutin, Thingstad, Van Wambeke, Marie, Slawyk, Raimbault & Claustre, 2002 (Limnol. Oceanogr.)

  14. 0,8 nM 2 nM 20 nM Limite de détection et sensibilité attendue Nécessite l ’achat d ’une centrifugeuse grand volume

  15. Container Radio-isotopes IFREMER

  16. Chlorophylle a µg l-1 Phosphate particulaire nM Absorption de phosphate nM h-1 Station "UPWELLING" au large du Maroc Station "M IO" en mer Ionienne Mission PROSOPE

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