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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) - PowerPoint PPT Presentation
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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
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)
P Indi
vat B
asin
Antar
es R
idge
Marion Dufresne core
M1 M4
M2
M3
Wide area bathym to show benthic sites
• MODELLED CIRCULATION • • Only OCCAM 1/12 comes close• • All show N flow just E of CP• • and E flow at 45°S
OCCAM 1/4° OCCAM 1/12°
Niiler float pic
Niiler surface drifter map with Crozet 1000m contour and Pollard ACC
pathway overlaid
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?
SWIFS2
SeaWiFS images
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
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)
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)
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
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
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
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”)
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
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
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
A possible cruise leg plan - CTDs
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