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Cruise 1: R/V Gyre04G03

Mechanisms Controlling Hypoxia on the Louisiana Shelf
2-8 April 2004

Port: Galveston, Texas
Mobilization: 1 April 2004
Cruise: 2-8 April 2004

Objectives

(a) to deploy three moorings containing oxygen, current velocity, and nitrate sensors;
(b) to conduct benthic respiration measurements aboard ship using waters collected near the moorings;
(c) to conduct a hydrographic survey in three zones of the Louisiana shelf;
(d) to obtain supplemental biological and geochemical measurements.

Scientific Party
Personnel

Scientists
Dr. Steve DiMarco: Chief Scientist
*Dr. Piers Chapman, LSU: Chemistry leader, nutrients, oxygen, salinity
Dr. Ann Jochens: Hydrographic Data Cop (QA/QC), watch leader
Dr. Barbara Smallwood: Geochemistry, watch leader
Dr. Tim Dellapena, TAMUG : Coring Leader
Dr. Les Bender, GERG: mooring deployment, navigation, ADCP

Technicians
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

Students
Brian Fielder: Geochemistry, TAMUG
David Finneran: Geochemistry, Water sampler
Erin Johnson: Microbial structure, Water sampler
Sudeshna Lahiry: Water sampler
Mike Lalime: water sampler, assist with NAS
Dino Marshalonis: C14 productivity, water sampling
Clif Nunnally: benthic productivity water sampler, TAMUG
Alicia Salazar: fluorometer, water sampler
Chrissy Stover: geochemistry/microbial, water sampler
Chihlin Wei: benthic productivity, water sampler, TAMUG

Winch
Billy Green-TAMUG: winch operator
TBD: TAMUG winch operator
*Waiver necessary for non-TAMU employees

Collecting Data
Data Collection

Instrumentation and equipment:
CTD/12 bottle Rosette (GERG)
Shipboard PAR (GERG) if available
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 (from Dr. Jay Pinckney)
Sediment traps (GERG)
Turner Fluorometer from Biggs (OCNG) and spare
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 (OCNG)
300(or 600)-kHz ADCP mooring: one one-day deployment (GERG)
Assorted Coring materials (Smallwood, Morse, and GERG)
DI water (Smallwood)
Digital cameras
Radio/CD player (Somebody with taste)

Mooring Measurements:
Instrumentation: 2 RCM9, 2 NAS-2E, Hydrolabs Datasonde, 2 sediment traps, 1 acoustic release
Current velocity: 2 depths
Temperature: 2 depths
Salinity: 2 depths
Nitrate: 2 depths
Oxygen: 2 depths
Turbidity, oxygen, downwelling irradiance, pH: near bottom (1 m above release)
Laptops (2) 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 salinity 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): Pb210
Morse/Smallwood/Mullenbach geochemistry samples

mooring diagram


Figure 1. Design for NOAA MCH mooring. Deployment 1: April - June 2004 (scheduled).

Figure 2. Proposed cruise track for NOAA-MCH Cruise 1, 2-8 April 2004.

Synopsis of sampling and deployment

The clusters of stations in Figure 2 represent the hypothesized three zones of hypoxia. A multi-instrumented mooring will be deployed near the center of each cluster. 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). After mooring deployment, a survey of the vicinity will be conducted. The 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 flowthrough 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. A 300(or 600)-kHz ADCP may be deployed in Zone C for 24 hours and recovered before the transit to Zone A. 56 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 a single 1.5-l Niskin bottle will be deployed at each station.