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LSU Researchers Explore Gulf Floor and “Most Complicated Continental Slope in the World”

When most people think of Louisiana as being unique, they think of Mardi Gras, crawfish, and Cajun culture. Few realize that what lies beneath the Gulf of Mexico along Louisiana’s coast is also unique, from the terrain and habitat to the animals living there. Two LSU researchers, however, dove down some 3,000 meters to explore it.

Researchers Harry Roberts and Bob Carney combed the most unique continental slope in the world to study some of the most singular animal communities on the planet – all just off the coast of Louisiana.

Roberts and Carney studied 11 different sites where oil and gas seep up from the bottom of the Gulf. In particular, they studied the animals that live near these “seeps.” These organisms include bacteria that feed on hydrogen sulfide gas, a by-product of the oil and gas seepage; tube worms, mussels and clams that serve as hosts to those bacteria; and shrimp, crabs, fish, snails, and starfish that, in turn, feed on the worms, mussels, and clams. These animal communities are unique because they only exist near these seeps, and because the bacteria at the base of the food chain are “chemosynthetic,” or grow without sunlight.

The large number of oil and gas seeps, the vast amount of salt under the Gulf floor near Louisiana’s coast, and the sediment dumped into the Gulf by the Mississippi River, make the continental slope off the coast of Louisiana unique.

“It’s the most complicated continental slope in the world, geologically,” Roberts said. “There are more seep communities off the coast of Louisiana than most places in the world. The salt, the oil and gas, and the sediment create a very dynamic geologic framework.”

Along with advancing science, the results of this research could also aid the oil and gas industry, as well as the Minerals Management Service, which gives the oil industry permission to drill and lay pipelines on the Gulf floor. Both the industry and the MMS want to know more about these seeps and the federally protected organisms that live near them in order to avoid drilling and performing other activities in those areas.

Roberts and Carney’s trip took place May 6 though June 2 of last year. They traveled as far as 2,750 meters (9,022 feet) below the surface of the Gulf in a submersible vehicle known as Alvin, which is operated by the Woods Hole Oceanographic Institute. Alvin, best known to the public for exploring the wreck of the Titanic, is well-known among the scientific community and is constantly in use worldwide by researchers who are able to pay for its use, either with grant or private funding.

Roberts and Carney received funding for their research through the MMS and the National Oceanic Atmospheric Administration’s Ocean Exploration Program. The use of the Alvin submersible was funded by NOAA. Since Alvin costs approximately $50,000 a day, the researchers’ use of it for nearly a month was a coup in the science world. Typically, a researcher will get to use Alvin for a few days or a couple of weeks.

As excited as they were about having Alvin for a month, Roberts and Carney admitted they felt some trepidation at being at sea for so long.

While conducting their research, Roberts and Carney lived on a 280-foot ship with 23 other scientists who were involved in their research and the ship’s crew of 17. When they were not using Alvin, things got a little boring, they said.

“When you’re not in the sub, you do your nails,” Carney joked. “You can process samples and do paperwork, but there is still a lot of time to fill. Eating is a big event.”

On most days, the two researchers used Alvin to take them down to the bottom of the Gulf. It took an hour and a half to an hour and 45 minutes to get to the floor of the Gulf, or the length of two Jimmy Buffet CDs, according to Roberts, who likes listening to music on the way down. But the submersible is small, Carney said, and seats a maximum of three people – two researchers and a pilot.

“Picture three people in the trunk of a Volvo,” he quipped.

In addition, because of the depths that Alvin was diving, the cabin can get very cold.

There are also a number of safety issues involved with Alvin. Since a complete dive takes a total of eight hours, the crew had to be sure that the weather would be good for that length of time. Alvin could not leave or return to the surface in bad weather. Also, there are oxygen and carbon dioxide levels to worry about, and the possibility of electrical, navigational, and communication failures.

The comforting factor, the men said, is that in the Gulf, the crew is considered “within rescue” by authorities. Sometimes, researchers take Alvin to oceans that are not considered as such.

Roberts, director of the Coastal Studies Institute at LSU and Boyd Professor of marine geology and geophysics/sedimentology, first came to LSU as a student in the 1960s and has been at the University ever since. Carney, professor of coastal ecology, has been at LSU since the 1980s. Both have been doing research on the Gulf’s oil and gas seeps and the animals that live in those areas since the 1980s.

“This project has been a lot of fun and scientifically very productive,” Roberts said. “In particular, the early cruises we took to the Gulf floor were fun because it seemed that every dive produced a new discovery. In those days, it was difficult to locate the sites we wanted to study. Today, because of technology that allows you to remotely evaluate the sea floor, the locations of hydrocarbon seeps are about 70 percent predictable.”

Other researchers on the trip represented Penn State University; Texas A&M University, Corpus Christi; University of Georgia; Harvard University; University of Vienna; Nova University; the Marine Biology Lab at Roscoff, France; TDI-Brooks, a geochemical services firm in College Station, Texas; St. Hubert High School; NOAA; and MMS.

Their cruise was documented on the NOAA Web site. From the NOAA home page, click on “Ocean,” then “NOAA Ocean Explorer,” then “Explorations,” then look under “2006 Signature Explorations,” and click on “Expedition to the Deep Slope.”

Kristine Calongne | Ernie Ballard | LSU Office of Public Affairs
Spring 2007

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