Research Objectives

• Mapping the extent of hypoxic water (< 2 mg/L) across the Louisiana and Texas inner to mid continental shelf, along with associated physical, chemical, and biological parameters. Associated rate measurements of biogeochemical processes.

Routine Measurements

• There are 80 to 100 stations from the Mississippi River delta on the east of the study area westward to the adjacent Texas coast south of Galveston. Additional stations have been added to this year's cruise at least to Matagorda Bay, TX due to the expected greater extent of hypoxia and the SEAMAP cruise documented hypoxia in that area.
• Standard hydrographic casts with a SeaBird CTD/rosette sampler for depth, temperature, salinity, dissolved oxygen, in vivo fluorescence, photosynthetically active radiation, percent transmission, optical backscatter. Additional hydrocast with YSI 6820 for close-to-bottom and near-surface measurements of depth, temperature, salinity, dissolved oxygen, and pH. Additional light meter cast for temperature, percent transmission, and % PAR. Calibration of salinity with discrete samples for analysis on PortaSal; calibration of oxygen with Winkler titrations. Instruments pre- and post-calibrated according to manufacturer guidelines. And the forever consistent, historical collection of Secchi disk depth.
• Discrete depth sampling from 5-L Niskin bottles on the CTD/rosette for nutrients, chlorophyll biomass, suspended sediments (organic and inorganic), phytoplankton, HPLC phytopigments.
• Underway mapping of current speed and direction through the water column with Acoustic Doppler Current Profiler systems.
• Underway mapping of near surface water temperature, salinity, in vivo fluorescence, percent transmission, pCO2, georeferenced with navigation data and suite of meteorological measurements (Multiple Integrated Data Assimilation System, MIDAS).

Projects

• Oxygen isotopes, respiration measurements
• N2/Ar ratios (denitrification) and organic matter (POM/DOM) distributions;
• Surface pCO2 underway, surface and bottom total alkalinity, pH, DIC
• Zooplankton distributions with a Lazer Optical Plankton Counter (LOPC), calibrated with Niskin samples and net tows
• Pseudo-nitzschia and domoic acid toxicity at different oxygen levels
• Phytoplankton growth limitation, sulfide concentration in bottom waters
• Sediment cores for paleoindicators of productivity and oxygen stress

Principal Investigators

• Nancy Rabalais, Louisiana Universities Marine Consortium
• Brian Roberts, Louisiana Universities Marine Consortium
• Geoff Sinclair, Louisiana Universities Marine Consortium
• Gene Turner, Louisiana State University
• Dubravko Justic, Louisiana State University
• Chunyan Li, Louisiana State University
• Brian Fry, Louisiana State Unviersity
• Don Scavia, University of Michigan

Funded by