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Cruise 3: R/V Gyre 04G08

Mechanisms Controlling Hypoxia on the Louisiana Shelf
20 August - 27 August 2004

Port: Galveston, Texas
Mobilization: 19 June 2004
Cruise: 20 - 27 August 2004

Students aboard the R/V Gyre

Dr. Steve DiMarco: Chief Scientist
*Dr. Piers Chapman- LSU: Chemistry leader, nutrients, oxygen, salinity
Dr. Matthew Howard: Hydrographic Data Cop (QA/QC), watch leader
Dr. Barbara Smallwood, Geochemistry Leader, watch leader
Dr. Antonietta Quigg-TAMUG- Water-column Biology
Dr. Gil Rowe: Benthic biology leader, dive master, ROV

Willie Flemings-GERG: mooring deployment, Marine Tech, NAS Specialist
Paul Clark-GERG: mooring deployment, CTD/Electronics Tech
Cris Schmidt: nutrient/oxygen/salt tech, NAS Specialist
Eddie Webb: CTD/electronics tech

Brian Fielder: geochemistry TAMUG
Sara Keach, GeochemistryTAMUG
Valerie Kiselkova: Ocean Engineering, water sampler
Erin Johnson: microbial structure, water sampler
Sudeshna Lahiry: Physical oceanography, water sampler
Mike Lalime: water sampler, assist with NAS and moorings
A. J. Seney: diver, water sampler TAMUG
Clif Nunnally: benthic productivity, water sampler TAMUG
Chrissy Stover: geochemistry/microbial, water sampler
Chihlin Wei: benthic productivity, diver TAMUG

Billy Green-TAMUG: winch operator
Steve Rodriguez-LUMCON: winch operator, RHIB Boat

Data Collection

Instrumentation and equipment:
CTD/12 bottle Rosette (GERG)
CTD/Transmissometer/4 bottle rosette (OCNG)
Shipboard PAR (OCNG)
CTD package (PAR, fluorescence, DO, OBS, T, S) (GERG)
Navigation computers (GERG)
Flow-through system computers (OCNG)
Salinometer and bucket (TAMU)
Autoanalyzer (6-channel) (TAMU)
Winkler Oxygen System (TAMU)
Thermosalinograph flow-through system (GERG)
Pump and filter for flow-through chlorophyll (at GERG)
Sediment traps (6) for redeployment (GERG)
Turner Fluorometer (OCNG) and Chelsea flowthrough (OCNG)
1.5-l bottle for bottom bottle oxygen (Bottle 1 and bottom tripped frame)
0.45 m boxcore (TAMUG)
Freezer bags for core samples: 1 quart bags
Microbial Structure and TEP sample supplies (Long and Thornton)
Shipboard ADCP (GERG) (Narrowband as backup)
Bottom-tripped frame and bottle (Pogo I; OCNG)
Assorted Coring materials (Smallwood and GERG)
C14: primary productivity (Quigg)
Digital cameras
Radio/CD player

Mooring Measurements: (see mooring schematic)
Instrumentation: 1 RCM9, 1 RCM7, 2 NAS-2E, 6 sediment traps
Current velocity: 2 depths
Temperature: 2 depths
Salinity: 2 depths
Nitrate: 2 depths
Oxygen: 2 depths
Laptop (1) for deployment initialization (GERG)

Survey measurements:
CTD: salinity, temperature, DO, transmission, chlorophyll, PAR (continuous)
Bottle: ammonia, nitrate, nitrite, phosphate, silicate, urea, dissolved oxygen, salinity
Bucket/Pogo salinity, DO (Pogo only), and nutrients
Particulate organic material and Dissolved organic material (lipids)
3-m salinity, temperature, chlorophyll (GERG system and Biggs' fluorometer) and SAIL
Boxcore (refrigerate samples for on-shore analysis): Smallwood/Dellapenna/Long core samples

Synopsis of sampling and deployments

The clusters of stations in Figure 2 represent the hypothesized three zones of hypoxia. A multi-instrumented mooring will be recovered and deployed near the center of Zone B. Benthic respiration will be monitored aboard ship using water samples drawn at each mooring site. Samples will be drawn from the incubation chambers at regular intervals (e.g., 6 hours). The hydrographic survey will consist of CTD/bottle casts, boxcores, and other measurements. Upon survey completion, we will transit to the next zone. A test station will be done on the transit to Zone C from Galveston. Bucket nutrients and salinity will be done between zones to locate the river plume. The ship's flow-through system and shipboard ADCP will be run for the duration of the cruise. Water column primary production will be measured at daytime sights in each zone. We hope for at least 8 sites per zone. Forty-minute incubations are planned, however, 20-minute incubations may be used. 58 CTD stations are planned. Depending on the location of the Mississippi River plume (imagery provided by Nan Walker at LSU) some stations in Zone A may be moved east and south of the delta. We will be doing microbial structure and geochemistry at 15 stations. For microbes, we will sample from top, middle, and bottom bottles. A bottom-tripped frame containing four 1.5-l Niskin bottles, CTD, and transmissometer will be deployed at each station. After the MCH work is completed we will go the Flower Gardens Bank National Marine Sanctuary to perform a side-scan and ROV survey of TABS Buoy V.