LSU Scientist On Team That Discovers Methane Ice Worms On Gulf Floor

The ice worms, found in waters 1,800 feet deep, were viewed by scientists diving in Harbor Branch Oceanographic Institute's submersible Johnson Sea Link.

Although scientists had hypothesized that bacteria might colonize ice mounds, called gas hydrates, this is the first time animals have been found living in the methane mounds. These hydrates are formed when water and natural gas, usually methane, come together where temperature is low and pressure is high, such as in deep ocean waters,and form a substance like dry ice.

The discovery of dense colonies of one- to two-inch-long, flat, pinkish worms, called polychaetes, raises speculation that the worms may be a new species with a pervasive and as yet unknown influence on the energy-rich gas deposits. The worms had burrowed into a mushroom-shaped mound of methane seeping up from the sea floor.

Using a research submarine on a National Oceanic and Atmospheric Administration-funded research cruise, scientists observed the worms using their two rows of oar-like appendages to move about the honeycombed, yellow and white surface of the icy mound.

Carney, director of Coastal Marine Institute, said that "scientists would immediately have two questions. First, what are they living on? Logically, they are eating a film of methane bacteria. The second part of the question is more intriguing: If they are living off the methane, why aren't snails and small shrimp in the area also feeding off the methane?"

"In the scheme of worms, these worms, Hesionidae, are large," Carney said. "They are very active. There are no other animals at that site. Though they are sitting on the side of a hydrated structure, the worms are not consuming the methane itself. They had drops of oil in their intestines. They may be scooping bacterial film off the rocks," he said.

Harry Roberts, LSU coastal studies professor, was the first researcher to recognize the existence of solid methane outcrops on the floor of the Gulf of Mexico, Carney pointed out.

Methane ice is usually buried deep in marine sediment. The Gulf of Mexico is one of the few places where hydrates can be found exposed on the ocean bottom, Carney said. Occasionally this seeping, solid methane bursts through in huge mounds, often six to eight feet across.

Each new discovery of animal life on the Gulf floor raises questions, Carney said. Where did they come from? Why are they in this specific spot and not somewhere else? Why do some underwater communities live on radioactive rocks? How do the oil companies' deep-water drilling operations affect them?

Minerals Management Service is charged with ensuring that colonies of fauna around seeps are not disturbed. MMS provides funding primarily to LSU and Texas A&M for ecological studies of seeps.

"People think of LSU research in terms of coastal marshes and wetlands," Carney said, "and don't realize that LSU is also engaged in deep-water research."

Geologically, the Gulf of Mexico "is a very exotic place. Ecologically, probably the most exotic places are the chemosynthetic communities about 100 miles off the coast of Louisiana, on the edge of the continental slope," Carney said.

The one week expedition in July was carried out aboard the Harbor Branch research vessel Edwin Link and sponsored by the NOAA National Undersea Research Center at the University of North Carolina at Wilmington and the Minerals Management Service of the U.S. Department of the Interior.

In addition to Carney and chief scientist Charles Fisher of Pennsylvania State University, principal investigators included Ian MacDonald of Texas A&M University, Steve Macko of the University of Virginia, and Alissa Arp and David Julian of San Francisco State University.

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