From: University of Georgia
Posted: Saturday, June 30, 2001
Life in the Gulf of Mexico is anything but calm. Hurricanes and tropical storms can clog shipping lanes and slam into populated shore areas, of course, but even more interesting things are happening deep beneath the surface. "Cold vents" of oil and gas seep from the ocean floor, methane hydrates form around gas vents and iridescent blue holes called brine pools freckle the sea floor.
Little is known about microbial processes in these environments, but a team of researchers, led by scientists at the University of Georgia and Georgia Tech, will travel to the Gulf in July and take a tiny submersible to the ocean bottom to learn more about processes that could have a major impact on such issues as the health of the seas and global warming.
Even better, those interested in the research and in the mysteries of the sea floor can follow the research daily on the World Wide Web˝where everything from discoveries and descriptions of work to stunning photographs will be posted.
"The first time I dove in the Gulf in a submersible, I was absolutely spellbound," said Dr. Mandy Joye, a biogeochemist in the University of Georgia's department of Marine Sciences. "Studying the nutrients and other elemental cycles associated with brine environments is, we think, very important. We know very little about the kinds of microorganisms that live in these hydrate environments."
The research cruise and dive are funded by the National Science Foundation, the National Oceanic and Atmospheric Association's National Undersea Research Program, the U. S. Department of Energy and the Petroleum Research Fund of the American Chemical Society.
Joining Joye in the research as co-chief scientists of the cruise will be Dr. Patricia Sobecky of Georgia Tech. Other researchers on the team are Dr. Joseph Montoya, also of Tech, along with Dr. Ian McDonald of Texas A&M University. Three graduate students and one undergrad from Joye's lab will also join in the trip.
The cruise will begin July 1 aboard the Harbor Branch Oceanographic Institute's research vessel Seward Johnson. Scientists will board the Seward Johnson in Gulfport, Miss., and head for sites in the Gulf of Mexico. Once there, they will begin a grueling schedule of twice-a-day dives of four hours each on a four-person submersible called the Johnson Sea Link II. Progress of the team can be followed until the end of the project on July 18 by logging on to http://www.at-sea.org/missions/extremes/preview.html.
"The study area is along the Louisiana and Texas continental shelf and slope at depths of between 500 and 1,000 meters," said Joye. "This entire area of the Gulf is a rich petroleum basin, and oil and gas drilling platforms are common in the area."
The 20-minute descent from the surface to the study sites is usually done in darkness, but when the flood lights of the Johnson Sea Link˝a vessel with an 18-inch-thick Plexiglas hull˝ come on, a dazzling world is as close as the tip of the submersible's robot arm. All along the area are fractures in the sea floor that bubble up methane gas˝one of the main atmospheric gases that contributes to global warming. A rise in the sea temperature of only a few degrees could dramatically alter the amount of methane being released, yet very little is known about the environments around these "cold seeps" or the bacteria that live there.
The research team will therefore be taking samples for study on such processes as methane oxidation, the rates of inorganic carbon dioxide fixation and nutrient concentrations. In addition, the scientists are collaborating with researchers from the Max Planck Institute for Marine Microbiology and the Monterey Bay Aquarium Research Institute on sulfur cycling at the same sites.
Even less may be known about so-called brine pools, deep pits along the sea floor filled with hypersalinated water, which is so much heavier than regular sea water that it stays together in what appear to be small but deep blue lakes. Brine pools form when warm, salty fluids migrate up through the sediments through fissures and then cool to ambient temperatures on reaching the surface.
The team will be studying two specific brine pools, one that is possibly old and stable and another that is young and quite active. The younger of the two brine pools has frequent eruptions of hot fluid, and life is scarce in the area. The other pool, however, is cooler, and there is a dense community of mussels around the pool's edge. (Tube worms are frequent around the methane vents, but they don't live around brine pools because of an absence of sulfides, which tube worms need to thrive.) Very little is known about the composition of these brine pools or the bacteria associated with them, however. Joye, in an earlier dive, dropped a 20-foot weighted line into one brine pool and never touched bottom.
"In order to sample sediments and brines, we use the robot arm of the Johnson Sea Link to collect sediment cores from areas around the hydrate environments and brine pools," said Joye. "We know next to nothing about the bacteria around the cold seeps."
While considerable basic science will be conducted on site, larger issues are involved. The Gulf of Mexico is basically a petroleum basin, filled with oil and gas, but nobody has ever, for example, measured the methane oxidation rate in the water column above these seeps. That rate could be crucial if global warming continues during the next century, because the vast amount of methane that is now oxidized before it reaches the surface of the ocean could then rise intact˝thus exacerbating global warming, Joye said.
Ice-column sampling has shown that there have been great swings in the amount of methane in the atmosphere in the past, so there is every reason to believe it can happen in the future as well.
This is Joye's fourth research cruise in this area of the Gulf, and problems can dog research when it takes place far from land on the sea floor. Her research vessel once spent 10 days trying to outrun a hurricane that developed a nasty habit of relentlessly following the ship until the storm finally veered away. In such circumstances, the research is simply lost.
Still the joys of a strange and beautiful world, along with the scientific knowledge to be gained, far outweigh the potential problems, said Joye. "The first time I went down, I think all I said was `Wow' for the first hour," she said. "They always tell you that the bottom of the sea is a desert, but then you get down there, and you find yourself watching mussels, eels, tube worms, fish and all kinds of invertebrates. On the way back up, the bioluminescence is just unreal."
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