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Primary Production and Phosphate Availability in Pacific Ocean

Study phytoplankton productivity, phosphate influence on carbon fluxes, and validate primary production model. Utilize JGOFS 14C method for daily rates calculation. Investigate phosphate flux, carbon uptake, and microbial community dynamics.

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Primary Production and Phosphate Availability in Pacific Ocean

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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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