Mechanisms Controlling Hypoxia on the Louisiana Shelf
22 - 29 March 2007

Port: Chauvin, Louisiana
Mobilization: 21 March 2007
Cruise: 22 - 29 March 2007

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Objectives

(a) to conduct a hydrographic survey in four dynamical regions of the Louisiana shelf;
(b) to conduct four 30-hour process oriented anchor stations;
(c) to conduct benthic respiration measurements aboard ship using waters collected near the moorings;
(d) to deploy short-term sediment traps;
(e) to obtain a series of boxcores;
(f) to obtain supplemental biological and geochemical measurements.

Personnel

Scientists
Dr. Steve DiMarco: Chief Scientist, Physics Leader, Day Watch Leader
*Dr. Piers Chapman- LSU: Co-Chief, Chemistry Leader, nutrients, oxygen, salinity
Dr. Matt Howard: Data Cop, Night Watch Leader

Technicians
Paul Clark: GERG, Electronics Technician
Eddie Webb: GERG, Electronic Technician
Blake Mackan: GERG, Nutrient Technician
Andrew Dancer, GERG: Electronic Technician Trainee
Marine Technician, provided by LUMCON

Students
Federico Alvarez, TAMUG, BO Graduate Stendent
Kelly Cole, TAMU: PO Graduate Student (female)
*Brian Gaas, Rutgers (Ammerman Student), BO Graduate Student
Mike Navatta: TAMU, CO Graduate Student
Clif Nunnally: TAMUG, BO Graduate Student, Biology Leader
Carolyn Wilson, TAMU, BO Graduate Student (female)
Xiaoqian Zhang: TAMU, PO Graduate Student

Winch Operators
Two provided by LUMCOM

(* = non-TAMU/TAMUG)

Funding Agent

National Oceanic and Atmospheric Administration (NOAA)

Participating Institutions

Texas A&M University: Department of Oceanography
Texas A&M University: Geochemical and Environmental Research Group
Louisiana State University: Department of Oceanography and Coastal Studies
Louisiana State University: Coastal Studies Institute
Texas A&M University at Galveston: Marine Biology Department
Rutgers, the University of New Jersey

Project Website: http://hypoxia.tamu.edu/hypoxia

Data Collection

Instrumentation and equipment (GERG):
12-bottle Rosette (with bottle 1 offset)
Pogo: CTD/Transmissometer/4 bottle rosette
CTD package (PAR, fluorescence, DO, OBS, T, S)
Aanderaa RDCP and frame: RDCP configured for waves and currents
Navigation computers
Flow-through system computers
Salinometer and bucket
Nutrient sample bottles and filters
(nutrients samples will be filtered and frozen on this cruise)
Winkler dissolved oxygen titration system (*chemicals prepared by GERG)
Titrator, sample bottles, chemicals
Pump and filter for flow-through chlorophyll
Chelsea fluorometer and flow-through equipment
0.45 m and 0.25 m (large and small) boxcores
Shipboard ADCP: 300 kHz Workhorse (shipped to LUMCON; installed on pole)
Ashtech GPS
Salinity Standard for Autosal

Other equipment and materials
Short-term sediment traps (Nunnally/Rowe to provide)
Assorted coring materials (Nunnally and Navatta)
Particulates filters (Navatta)
Chlorophyll filters (Quigg/Alvarez)
1-m intake system for MIDAS flow-through system (LUMCON)
Vacuum pump/filtration system (DiMarco)
Digital cameras, DVDs (All)
Radio/CD player (DiMarco)

Mooring Measurements (deployed on separate cruise):
Instrumentation: 1 RCM9, 2 Satlantic ISUS nutrient sensors, 2 RBR T/S/DO sensors, sediment traps at three depths
Current velocity: 1 depth
Temperature: 3 depths
Salinity: 3 depths
Nitrate: 2 depths
Oxygen: 3 depths

Survey measurements:
CTD (continuous): salinity, temperature, DO, transmission, chlorophyll, PAR
Bottle: ammonia, nitrate, nitrite, phosphate, silicate, urea, dissolved oxygen, salinity
Bucket/Pogo salinity, DO (Pogo only), and nutrients
3-m salinity, temperature (MIDAS), chlorophyll (Chelsea fluorometer)
Boxcore (refrigerate samples for on-shore analysis): Navatta core samples
All nutrient samples will be filtered, frozen, and stored for on-shore chemical analysis

Additional measurements
J. Ammerman: enzymes (phosphotase)
T. Bianchi: DOC, Total suspended material (supply weighed/combusted filters), lignin, stable isotopes
A. Quigg (TAMUG): chlorophyll a, FiRE, diurnal curves, nutrient addition assays,
L. Osterman (USGS): paleohypoxia core samples (deep box core stations): will provide core tubes
C. Harris (VIMS): grain size samples (core grabs, upper 2 cm)

Figure 1. Locations of NOAA/TAMU M8 CTD and anchor stations. Shown are the 10, 20, 30, 40, and 50 m isobaths derived from the DBDB2 bathymetry database,

Figure 2. Map of central and eastern Texas-Louisiana Shelf showing locations of proposed mooring sites: D, and C. Mooring C will be deployed by GERG on a separate cruise. Also shown are the LUMCON C6 Site, TABS Buoy R, and the 10, 20, 30, 40, and 50 m isobaths derived from the DBDB2 bathymetry database.

Synopsis of cruise

This cruise is the first of three NOAA-funded cruises scheduled for 2007 on the R/V Pelican. The main objective of this research is to investigate the mechanisms that control the onset, duration, and breakup of the hypoxia that occurs off of coastal Louisiana each summer. The methods include deployment of real-time reporting instrument systems, an extensive coupled biological/physical/sediment numerical modeling effort, and shipboard process studies (to complement the real-time observations). This cruise constitutes the first hydrographic survey and will consist of CTD/bottle casts, boxcores, and other measurements at about 40 stations between the Southwest Pass (Mississippi River delta) and western coastal Louisiana (near Cameron). Depending on time and weather considerations, we have planned four 30-hour anchored stations spread across the region. Benthic respiration will be monitored aboard ship using water samples drawn at each anchor station. Samples will be drawn from the incubation chambers at regular intervals (e.g., about every 6 hours). A test station will be done on the transit to the first CTD station to train graduate students on CTD and rosette sampling and test scientific apparatus. The ship's flow-through system will be run for the duration of the cruise. Bucket nutrients and salinity may be done between planned stations to best locate the river plume. A bottom-tripped frame containing four 1.5-l Niskin bottles, CTD, and transmissometer will be deployed at each station in addition to the 12-bottle rosette. We will do boxcores in several of the CTD locations to target benthic and sediment processes. We expect four to seven core stations. An RDCP current profiler and short-term sediment trap will be deployed at the start of each anchor station. We will also conduct a number of additional complementary and related experiments during the course of this cruise. These experiments involve the collection of additional water and sediment samples for analysis both at sea and on shore. The collection of these samples will not reduce in number or jeopardize, in any way, the collection of the base samples required to achieve the study objectives.

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