Investigating the Horizontal Distribution of Hydrographic Properties of the Texas-Louisiana Shelf Using an Undulating Towed Vehicle

摘要

Observations of salinity, dissolved oxygen (DO), chlorophyll-a, and CDOM fluorescence were collected using an Acrobat (Sea Sciences Inc.) undulating towed vehicle during an oceanographic survey in June 2012. These observations were analyzed to investigate the horizontal and vertical spatial variability and examine the relationship of physical and biological factors with the distribution of dissolved oxygen concentration. Equipped with a CTD and multiple sensors, the instrument package produced high spatial resolution (~200 m) vertical sections along 16 cross-shelf lines that were distributed along the Texas-Louisiana Shelf from Matagorda Bay, Texas to the Mississippi River Delta at Southwest Pass, Louisiana. Characteristics associated with the freshwater plume of the Mississippi River are confined to small areas of the eastern shelf, which led to a discernible east-to-west gradient between the analyzed properties. As a result of strong salinity-based stratification, the east-shelf contained low surface salinity, near-bottom hypoxia, and maximum chlorophyll-a and CDOM fluorescence values above the halocline. Contrary to this, the west-shelf was characterized by weak stratification, no near-bottom hypoxia, and maximum chlorophyll-a and fluorescence values beneath the main halocline and near the ocean floor. If it is not monitored and remediated, hypoxia can bring about detrimental impacts on aquatic life and can lead to distressing impacts on the ecosystem. This research comprises a portion of the Mechanisms Controlling Hypoxia Project, funded by NOAA since 2003, whose objective is to characterize the principal physical drivers of hypoxia in the northern Gulf of Mexico.