Tricho

Ship

R/V Oceanus

Vehicles

Cruise Party

Dennis McGillicuddy: Chief Scientist, Principal Investigator
Woods Hole Oceanographic Institution Bigelow 209A, MS#11 Woods Hole, Ma. USA 02543
+1 508 289 2683
mcgillic@whoi.edu

Departure: Woods Hole on Oct 1, 2010

Arrival: Bridgetown, Barbados on Oct 21, 2010

Supporting documentation:

»Tricho_cruise_planning_July_5.pdf

Operations Area:

Lat/Lon:

Depth Range: min / max (m)

Will the vessel be operating within 200 NM of a foreign country? yes
Are visas or special travel documents required? no

Science objectives

The diazotroph Trichodesmium spp. constitutes a major pathway of nitrogen flow into marine planktonic ecosystems, but estimates of its impact on global nitrogen budgets vary widely. Sampling is made difficult by the fragility of the organism with the consequence that Trichodesmium spp. are difficult to manipulate in both field and laboratory experiments. Optical methods that sample the organism nondestructively are thus appealing. A recent transatlantic survey using the Video Plankton Recorder (VPR) revealed unexpectedly high abundance of Trichodesmium spp. at depth, suggesting the vertical distribution of the organism within the euphotic zone may be more uniform than previously thought (Davis, C.S. and McGillicuddy, D.J., 2006. Transatlantic Abundance of the N2-Fixing Colonial Cyanobacterium Trichodesmium. Science, 312: 1517-1520). Application of a simple bio-optical model of productivity to the observed profile of abundance suggests the depth-integrated nitrogen fixation rate could be three to five times higher than that based on the canonical profile of exponential decrease in abundance with depth. However, the observations described in Davis and McGillicuddy (2006) come from a latitude range where Trichodesmium spp. are not especially abundant. This raises a key question: is there a similar vertical distribution in waters further to the south, where Trichodesmium spp. are an order of magnitude more abundant overall? If so, are the deep populations actively fixing nitrogen? If so, the implications for the global nitrogen budget would be substantial.

To answer these questions, we will undertake two cruises to survey the waters of the southern Sargasso Sea and tropical Atlantic, where Trichodesmium spp. are commonly found in high abundance. Along-track VPR measurements will document the abundance and distribution of the organism on the scale of meters to thousands of kilometers. Standard hydrographic station work will provide for comparison of VPR-based estimates with microscope counts, as well as some additional in situ optical methods. A combination of nifH gene expression assays and direct determinations of N2-fixation rates will be made to assess whether or not the deep populations are actively fixing nitrogen. These observations will be synthesized in the context of an eddy-resolving numerical model. This will permit investigation of the mechanisms controlling the vertical and horizontal distribution and abundance of Trichodesmium spp. at multiple scales, including the enigmatic association of relative maxima in abundance with anticyclonic eddies (also described in Davis and McGillicuddy, 2006). Moreover, integration of these observations into the numerical model will facilitate revised estimates of nitrogen fixation by Trichodesmium spp. in the North Atlantic.

Science Activities

Departing from Woods Hole, we will set a course for BATS 31 40N, 64 10W.  VPR will be deployed upon crossing the shelf break.  XBTs will be deployed hourly.  VPR will be recovered each day at 0930 so CTD station work can begin promptly at 1000.  Upon completion of CTD/pump station work, VPR will be redeployed and underway sampling will recommence.

After sampling at BATS, we will proceed southward along 64W to 20N, then turning southeastward to 10N, 45W.  Alongtrack sampling is flexible, and we will adjust our course according to satellite altimetry and SST / ocean color imagery.

Pre-cruise planning meeting: Visit WHOI

JULY 14 @ 1400 hrs at 38 Water St. 2nd floor conference room.

Stations:

Funding Agency: NSF #OCE-0925284

- added NSF #OCE-0925284 on Jun 24, 2010 6:21 AM by
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R/V Oceanus

Shipboard Equipment

ADCP 150 kHz
ADCP 75 kHz
Bathymetry System 12 kHz
Bathymetry System 3.5 kHz
Deionized Water System
Fume Hood
Sippican XBT System (Mark 21)
Science Underway Seawater System

CTD/Water Sampling

911+ Rosette 24-position, 10-liter bottle Rosette with dual T/C sensors
Biospherical underwater PAR (1000m depth limit) with reference Surface PAR
SBE43 oxygen sensor
Seapoint STM turbidity sensor
Wet Labs C*Star transmissometer (660nm wavelength)
Wet Labs ECO-AFL fluorometer

Critical CTD Sensors: 

CTD-Related Equipment

ECO/AFL and STM sensor (WHOI owned)

Hydrographic Analysis Equipment

Salt Bottles (2 cases of 125 ml provided)

MET Sensors

Air temperature
Barometric Pressure
Precipitation
Relative Humidity
Short Wave Solar Radiation
Wind speed and direction

Sample Storage

Chest Freezer (Household type) 0°F
Freezer -70°C 3.2 cu. ft. ea.
Refrigerator 8.6 cu. ft.


Storage Notes: Need 2 chest freezers (-20C) in main lab.

Navigation

Will you be using Long Base Line (LBL) navigation? no

Will you be using Doppler/GPS navigation? yes

Winches

CTD Winch with .322" Electro-mechanical wire

Winch Notes: VPR winch and block

Winch Notes: VPR cable: 3 fiber optic, 3 copper 0.322" opto-electric

Slip ring required? yes	Number of conductors: 3
Non-standard wire required? yes	Type: VPR cable
Traction winch required? no	Describe:

Other Science Vans:

Other Science Vans:

Science Van 1
Type/size: General purpose lab van		Location: main deck
Water: yes		Power:20A
Science Van 2
Type/size: Berthing		Location:
Water:		Power:

Specialized Deck Equipment

Mooring Deployment/Recovery Equipment Required: no	Type:
Cruise Specific Science Winch Required: no	Type:
Nets Required: no	Type:

Over the Side Equipment

Will you be bringing any equipment (winches, blocks, etc.) that lowers instruments over the side? yes

Details: VPR winch and block

Special Requirements

Elecrical Power: yes	Identify: Power for VPR
Equipment Handling: no	Identify:
Inter/intraship Communications: no	Identify:
Science Stowage: no	Identify:
Water: no	Identify:

Additional Cruise Items/Activities

Explosive Devices: no Portable Air Compressors: no Flammable Gases: yes

Small Boat Operations: no SCUBA Diving Operations: no

Hazardous Material

Will hazardous material be utilized? yes

Radioactive Material

Radioiosotopes: no

Additional Information

Is night time work anticipated on this cruise? yes

Specialized tech support (Seabeam, coring, other): VPR tech

Other required equipment and special needs:  pumping system to be attached to CTD

2 incubators with fold-down legs to be set up on aft deck

6 wire baskets: 3 on 01 deck for carboy storage, 3 on main deck for pump hose.

LN2 delivery in Barbados to recharge dewars for transit back to WHOI.


Date Submitted: Jul 19, 2010 2:30 PM