Mechanisms Controlling Hypoxia on the Louisiana Shelf is a three-year project funded by the National Oceanic and Atmospheric Administration (NOAA) Coastal Ocean Program. The program investigators are from Texas A&M University, Texas A&M University at Galveston, and Louisiana State University. The study comprises comprises an integrated, multidisciplinary, numerical and observational study of the competing mechanisms of hypoxia, which will investigate the relative importance of both nitrate inputs and physical factors, such as winds, river flow, and local circulation patterns. The central hypothesis that will be tested is that the region affected by hypoxia may be separated into three zones, controlled by chemical, biological, and physical processes, respectively.
.
The objectives are to investigate: (i) how stratification changes with forcing by freshwater and local winds; (ii) how respiration rates across the region are related to stratification; and (iii) how the combination of the physical controls and in situ respiration rates interact to maintain the hypoxic zone.
.
The work will include a combination of high-resolution physical model, a model of the biogeochemical regime, and in situ sampling. The latter will include moored measurements above and below the pycnocline to monitor the oxygen and nitrogen concentrations at three sites, along with the associated currents. Sedimentation rates of organic and inorganic material will be followed with suspended traps, while in situ benthic respiration rates will be measured using a benthic lander. Additionally, a series of hydrographic stations will be occupied around each mooring site to examine the local scales of interaction.
.
Initially, the models will be tested using historical data in a series of process experiments. The field measurements will be used to improve the models and as a test of their ability to predict how the system changes. It is anticipated that the results from this work will enable researchers to differentiate regions controlled by biological or chemical activity from those where physical processes such as stratification are more important. This work has a direct bearing on the likely effectiveness of the proposed remediation process for the region.
