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Why a study of the south east pacific?

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Why a study of the south east pacific ?

      The gyre displays the most extreme oligotrophic conditions of the world ocean (surface equivalent to the Med Sea).

      The area is dust (iron)-free:  Most extreme iron/ nitrate limitations of the tropical ocean”Pure” atmosphere : very good for ocean color sensor cal/val (SeaWiFS, MERIS, MODIS)

      Optics, biology, bio-geochemistry of the area remain largely unknown

  Unexpected features can be expected….      Adaptation to extreme conditions      New species/ untypical functional adaptation.

  SCORPIO (along 28°S and 43°S) and WOCE (32°S; 17°S) : hydrology and tracers of water masses

       The South East Pacific remain an under sampled ocean (call to participation in the SPG and boundaries)

  

Oligotrophy in the South Pacific Gyre (Olipac Cruise)

•Surface (0-100m) nitrate below detection limit

•Surface phosphate > 0.1 M)

•DCM very deep (>120 m, up to 150-160m)

•Extremely clear waters : Ze ~125m.

•In UV, Kd is extremely low <=> CDOM / and non-algal particles very low

•Prochlorococcus fluorescence very low in surface

•Very clear diurnal cycle in certain optical properties

•Very clear diurnal cycle in photochemical quantum efficiency (controlled by iron limitation) ???

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1

164°W 132°W 100°W 68°W4°N

20°S

44°S

26°S; 115°W 0.019 mg Chla m-3

Chavez et al., 1995

26°S; 115°W

0.019 mg Chla m-3

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1

164°W 132°W 100°W 68°W4°N

20°S

44°S

16°S; 150°W : 0.050 mg Chla m-3

SeaWiFS Nov. 1998SeaWiFS May 1998

Signorigni et al. 1999

SeaWiFS Nov. 1998

Signorigni et al. 1999

MeasurementsJan - Feb 1991

26°S; 115°W

0.019 mg Chla m-3

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1

164°W 132°W 100°W 68°W4°N

20°S

44°S

16°S; 150°W : 0.050 mg Chla m-3

Three main topics : the strengths

• From viruses to zooplankton• Variety of tools : molecular, pigments, microscopic….

• C, N, P, Si, Fe : investigated simultaneously (stocks and fluxes)

BIODIVERSITY

BIOGEOCHEMISTRY

BIO-OPTIC

• Cal/val for 4 satellites (SeaWiFS, MERIS, MOTIS-A, MODIS-T

• True N2 fixation measurements• Estimation of particle stock from ~0.5 m to mm• Aerosol measurements

• Study of the optical properties of untypical waters • Bio-optics vs bio-geochemistry.

                   

BIOSOPE : sponsors & international collaborations

• University of Concepcion (Ulloa / Farias / Grobb)

• IAEA (Miquel / Gasser)

• SCRIPPS (Stramski / Roemich)

• Rutgers (De Varga / Falkowski)

• University of Halifax (Lewis)

• Woods Hole (Repeta)

• NASA Greenbelt (Hooker)

• NOAA (Engler)

• University of Warwick (Scanlan)

• University of Hawaii

• USSC

UH/UCSC and BIOSOPE : proposition of collaborations

• Bob Bidigare- Analysis of photoheterotrophy pigments (BChl a and trans-retinal)- Flow cytometric enumeration of BChl a-containing bacteria

• Dave Karl- Analysis of phosphorus pool components (low-level phosphorus (MAGIC), particulate organic phosphorus and dissolved organic phosphorus)

• Grieg Steward- Genetic characterization of viruses

• Mike Rappé- Analysis of 16S rDNA diversity

• Jonathon Zehr- Analysis of nif gene diversity

Objectives of (short !)Presentations and of the meeting

• To refine the scientific objectives

• To develop unanticipated collaborations

• To establish the “final” scenario of the cruise

• To prepare the “document of preparation” for IFREMER

Location and duration of station

Succession of operations on station