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CROZEX- CROZet circulation, iron fertilization and EXport production experiment

CROZEX- CROZet circulation, iron fertilization and EXport production experiment. Three cruises on RRS Discovery: Leg 1 - 1 November 2004 to mid-Dec Leg 2 - mid-December to late Jan 2005 Leg 3 - benthic cruise not yet scheduled. CROZEX Main objectives and PIs. Circulation and mixing (Pollard)

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CROZEX- CROZet circulation, iron fertilization and EXport production experiment

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  1. CROZEX- CROZet circulation, iron fertilization and EXport production experiment • Three cruises on RRS Discovery: • Leg 1 - 1 November 2004 to mid-Dec • Leg 2 - mid-December to late Jan 2005 • Leg 3 - benthic cruise not yet scheduled

  2. CROZEXMain objectives and PIs • Circulation and mixing (Pollard) • Fe source, distribution (Statham) and speciation (Fones) • Phyto- (Lucas) and zooplankton (Fielding) biomass and community structure • Export flux (Sanders, Lampitt) • Benthic response to export (Billett)

  3. Indivat Basin P Antares Ridge

  4. Marion Dufresne core M4 M1 M3 M2

  5. Wide area bathym to show benthic sites

  6. OCCAM 1/4° OCCAM 1/12° • MODELLED CIRCULATION • • Only OCCAM 1/12 comes close • • All show N flow just E of CP • • and E flow at 45°S

  7. Niiler float pic Niiler surface drifter map with Crozet 1000m contour and Pollard ACC pathway overlaid

  8. Mixing and source of Fe • Sharp spatial onset of bloom at NE corner of Isle de l’Est • Mixing and entrainment in lee of island? • Source on Antares Ridge?

  9. SWIFS2

  10. SeaWiFS images

  11. Physical objectives & techniques • Determine circulation around CP • Find and delineate mixing areas, quantify mixing rates • Tools: hydrography (CTD, SeaSoar), LADCP, moorings (McLane Moored Profiler = M3, CMs), floats*, models (OGCMs, tides), altimetry *italics = needs funding

  12. Fe objectives • 3-D full depth total Fe distribution with respect to water masses - ‘age’ water • Identify shallow benthic source and determine pathways to the surface • Investigate speciation of iron and Fe complexing ligands close to sediment and changes during dispersion • Look in detail at transfer of iron from sediments to water column (PhD)

  13. Fe techniques • Towed Fe fish • Fe iron analyser (15 minutes per sample) • Fe friendly (Ti) rosette and CTD • Benthic Boundary Layer Sampler (BBLS) • Size fractionation - dissolved and soluble • Fe speciation and ligand concentration • Ra tracking of water masses (with WHOI) • Sediment cores (for PhD)

  14. Phytoplankton objectives • Biomass, community structure and distribution associated with the bloom • Rate of size-fractionated production • Rates of new and regenerated production • f-ratio calculation • Physiological response to Fe limited and replete regions • Detection of phytoplankton Fe limitation

  15. Phytoplankton techniques • 6+ samples from every CTD cast for size-fr chl, HPLC, POC/N, particle absorbance, preservation for taxa, cell carbon • C fixation (+Si uptake) - daily incubations • N uptake and C:N fixation/uptake rates • Ammonium regeneration and nitrification • P vs E (14C, 15N) from midday daily CTD • FRRF (profiles, underway, lab/incubations) • SDS-PAGE samples for flavodoxin

  16. Zooplankton objectives • Biomass, distribution and species composition • Microzooplankton and “microbial loop” processes • Mesozooplankton • Community (herbivorous) grazing rates • Control on primary production as alternative to Fe / nutrients / light? • Contribution to export? - eg. via particle transformation, faecal pellet production

  17. Zooplankton techniques • 2-4 vertical nets after every CTD cast • preserve for taxonomy, freeze for Carbon • pick for gut fluorescence • Daily gut evacuation rate experiment • OPC on SeaSoar (mesozooplankton) • Up to 8 LHPR tows • Flow cytometry & radioisotopes • (“microbial loop”)

  18. Export objectives • Quantify the export flux from above the seasonal thermocline • Estimate mid-water re-mineralisation • Assess detrital quality for benthic community • Quantify rain rate to the sea floor • Quantify burial rate

  19. Export techniques • f-ratio (see phytoplankton) • Seasonal euphotic zone nutrient deficits • 234Th and POC from CTD and SAPS (dedicated casts to 1000m every ~2 days) • Drifting pelagra traps (~4 day deployments) • 3 moored sediment traps at M1, M2, M4 • Cores from control and bloom sites

  20. Work on both/all legs • Casts for CTD, nutrients etc • Zooplankton nets after each CTD • Daily incubations (dawn CTD) and PvE (noon with profiled FRRF) • Casts with Ti rosette for Fe (~12) • Casts for 234Th followed by SAPS • Pelagra trap ~4 day deployments • CO2 underway and profiles • Occasional benthic trawls • Build time series at M1/4 and M2

  21. A possible cruise leg plan - CTDs

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