CROZEX-%20CROZet%20circulation,%20iron%20fertilization%20and%20EXport%20production%20experiment

1
(No Transcript)
2
(No Transcript)
3
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

4
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)

5
(No Transcript)
6
Indivat Basin
P
Antares Ridge
7
Marion Dufresne core
M4
M1
M3
M2
8
Wide area bathym to show benthic sites
9
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 45S

10
Niiler float pic
Niiler surface drifter map with Crozet 1000m
contour and Pollard ACC pathway overlaid
11
(No Transcript)
12
Mixing and source of Fe

• Sharp spatial onset of bloom at NE corner of Isle
  de lEst
• Mixing and entrainment in lee of island?
• Source on Antares Ridge?

13
SWIFS2
14
SeaWiFS images
15
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
16
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)

17
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)

18
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

19
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 CN 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

20
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

21
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)

22
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

23
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

24
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

25
(No Transcript)
26
A possible cruise leg plan - CTDs