Underwater Watchguards

Jun 25, 2014

Gliders target dead zone on a mission to measure and monitor.

Researchers from Texas A&M University set sail June 17 from Galveston with a fleet of new underwater robotic devices to measure the extent of this season’s “dead zone” in the Gulf of Mexico.

Foremost in their arsenal of instruments are four Slocum gliders, sleek, yellow AUVs (for Autonomous Underwater Vehicles) that send continuous observations of temperature, salt and oxygen concentrations back to shore very six hours. Their deployment ushers in a new era in ocean observing for the Gulf of Mexico, say Steve DiMarco and his team of scientists and technical crew members.

This is the 12th summer and 33rd cruise for DiMarco, lead investigator and a College of Geosciences oceanographer whose previous research in the Gulf of Mexico has made him a leading authority on hypoxia in the region.

The term hypoxia, DiMarco explains, is a condition in which dissolved oxygen concentrations dip low enough to harm marine life. Occurring in various degrees of severity every summer, hypoxic conditions are caused by the combination of multiple factors, which include nutrients from fertilizer runoff and the amount of freshwater discharged by the Mississippi River and coastal winds in the northern Gulf of Mexico. These factors all work to reduce the amount of oxygen near the ocean bottom. The area is called the dead zone because low oxygen conditions can lead to decimating massive amounts of marine organisms.

This expedition marks a departure from the previous forays. Researchers from Texas A&M University, Texas A&M-Galveston, other Gulf state universities and government organizations have joined forces to contribute personnel, scientific expertise and ships, in addition to the gliders. Using instruments ranging from a device developed in the 1920s to the new gliders, the scientists hope to provide the most thorough analysis of the dead zone ever gathered.

“The beauty of this system,” DiMarco explains, “is that the gliders will stay in the Gulf for several weeks, gathering more detailed results than we ever could using other instruments. Gliders can collect data for a much longer period than is possible from a boat, and they do it more efficiently and for a lot less money.

Using satellite-based communication systems, land-based pilots guide the vehicle from computers in College Station.

On the first leg of the expedition the research vessel Manta will cover the area beween Matagorda, Texas and the Mississippi river delta. The crew will deploy three gliders in addition to taking temperature, salinity, depth and other measurements with more traditional instruments such as rosettes and a device called an Acrobat that looks and functions like an underwater miniature biplane.

In late June, researchers from the Gulf Integrated Spill Research (GISR) consortium, using the research vessel Pelican, will deploy one glider provided by Texas A&M University-Galveston.

“The Galveston glider,” DiMarco says, “is built for deeper waters.” All four gliders are set to sail around the Texas-Louisiana coast, sensing and measuring its dead zone for up to 10 weeks.

“This has never been done before, and with so many rigs and other obstacles that the they have to maneuver around,” DiMarco says, “this will be a true test of the gliders.”

He also notes that combining forces with other universities along the Gulf Coast will greatly enhance their ability to collect the most data ever gathered on the dead zone.

Hypoxic events can be economically devastating for the fishing and recreational industries throughout the Gulf Coast region in addition to upsetting delicate ecosystems, which can take years to recover.

More thorough examination of the causes and effects of hypoxia can help industry, legislators and policy makers better monitor and control upstream factors that influence the level of oxygen in Gulf waters.

NOAA’s Center for Sponsored Coastal Ocean Research has funded the Mechanisms that Control Hypoxia project since 2003 and is providing additional base funds for the glider experiment.

Partners in the expedition are the following. 
• Integrated Ocean Observing System and National Centers for Coastal Ocean Sciences provided partial funding for the glider experiment.
• Teledyne Webb Research Corporation built the gliders and donated one for the experiment. 
• The Gulf of Mexico Coastal Ocean Observing System is delivering the glider data in real-time.
• The Louisiana State Scan Laboratory is providing imagery to the ship to assist in cruise planning and operations. 
• The University of Southern Mississippi is a scientific contributor.
• The Louisiana Universities Marine Consortium operates the R/V Pelican.
• NOAA Flower Garden Banks National Marine Sanctuary operates the R/V Manta. 

By Karen Riedel

Dr. Steven DiMarco
Professor and Ocean Observing Team Leader

Karen Riedel
Communications Manager