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Why a study of the south east pacific ?

Why a study of the south east pacific ?. 1. 6. 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:

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Why a study of the south east pacific ?

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  1. Why a study of the south east pacific? 1 6

  2. 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: • ØMost extreme iron/ nitrate limitations of the tropical ocean • Ø”Pure” atmosphere : very good for ocean color sensor cal/val (SeaWiFS, MERIS, MODIS) • ·Optics, biology, bio-geochemistry of the area remain largely unknown • ØUnexpected features can be expected…. • §Adaptation to extreme conditions • §New species/ untypical functional adaptation. • ØSCORPIO (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) 1 6

  3. Oligotrophy in the South Pacific Gyre (Olipac Cruise) • Surface (0-100m) nitrate below detection limit • Surface phosphate > 0.1 mM) • 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) ???

  4. 164°W 132°W 100°W 68°W 4°N 20°S 44°S 26°S; 115°W 0.019 mg Chla m-3 1 6

  5. Chavez et al., 1995

  6. 164°W 132°W 100°W 68°W 4°N 20°S 44°S 16°S; 150°W : 0.050 mg Chla m-3 26°S; 115°W 0.019 mg Chla m-3 1 6

  7. SeaWiFS May 1998 SeaWiFS Nov. 1998 Signorigni et al. 1999

  8. SeaWiFS Nov. 1998 Measurements Jan - Feb 1991 Signorigni et al. 1999

  9. 164°W 132°W 100°W 68°W 4°N 1 6 20°S 44°S 16°S; 150°W : 0.050 mg Chla m-3 26°S; 115°W 0.019 mg Chla m-3

  10. BIODIVERSITY BIOGEOCHEMISTRY BIO-OPTIC 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) • True N2 fixation measurements • Estimation of particle stock from ~0.5 mm to mm • Aerosol measurements • Cal/val for 4 satellites (SeaWiFS, MERIS, MOTIS-A, MODIS-T • Study of the optical properties of untypical waters • Bio-optics vs bio-geochemistry.

  11. 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 BIOSOPE : sponsors & international collaborations

  12. 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

  13. Location and duration of station Succession of operations on station 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

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