Dr. Craig Cary
Most of us are familiar with "Old Faithful" in Yellowstone National Park. This famous geyser erupts several times a day. It spouts a column of water heated by volcanic rock deep within the Earth's crust.
A hydrothermal vent is a geyser on the seafloor. It continuously spews super-hot, mineral-rich water that helps support a diverse community of organisms. Although most of the deep sea is sparsely populated, vent sites teem with a fascinating array of life. Tubeworms and huge clams are the most distinctive inhabitants of Pacific Ocean vent sites, while eyeless shrimp are found only at vents in the Atlantic Ocean.
The first hydrothermal vent was discovered in 1977. They are known to exist in the Pacific and Atlantic oceans. Most are found at an average depth of about 7,000 feet (2,100 meters) in areas of seafloor spreading along the Mid-Ocean Ridge System - the underwater mountain chain that snakes its way around the globe.
How do hydrothermal vents form? In some areas along the Mid-Ocean Ridge, the gigantic plates that form the Earth's crust are moving apart, creating cracks and crevices in the ocean floor. Seawater seeps into these openings and is heated by the molten rock, or magma, that lies beneath the Earth's crust. As the water is heated, it rises and seeks a path back out into the ocean through an opening in the seafloor.
As the vent water bursts out into the ocean, its temperature may be as high as 750°F (400°C). Yet this water does not boil because it is under so much pressure from the tremendous weight of the ocean above. When the pressure on a liquid is increased, its boiling point goes up.
Chimneys top some hydrothermal vents. These smokestacks are formed from dissolved metals that precipitate out (form into particles) when the super-hot vent water meets the surrounding deep ocean water, which is only a few degrees above freezing.
So-called "black smokers" are the hottest of the vents. They spew mostly iron and sulfide, which combine to form iron monosulfide. This compound gives the smoker its black color.
"White smokers" release water that is cooler than their cousins' and often contains compounds of barium, calcium, and silicon, which are white.
Geologists are intrigued by how rapidly vent chimneys grow - up to 30 feet (9 meters) in 18 months. A scientist at the University of Washington has been monitoring the growth of "Godzilla," a vent chimney in the Pacific Ocean off the coast of Oregon. It reached the height of a 15-story building before it toppled. It is now actively rebuilding.
There are many other reasons why scientists want to learn more about hydrothermal vents. These underwater geysers are believed to play an important role in the ocean's temperature, chemistry, and circulation patterns.
Scientists also are fascinated by the unusual life that inhabits vent sites. These creatures who live in darkness, from bacteria to tubeworms, may light the way to the development of new drugs, industrial processes, and other products useful to us all.
For More Information:Dive in to our on-line expeditions to hydrothermal vents!
See the video clip "Life in Extreme Environments."
Faculty Research: Dr. Craig Cary
In a steamy underwater hell west of Costa Rica, weird deep-sea worms survive temperatures nearly hot enough to boil water - too hot for any other complex creature on Earth - and they don't care if their 'heads' are two-and-a-half times cooler than their 'tails,' a University of Delaware researcher reports in the Feb. 5, 1998 issue of Nature.
The study, directed by molecular biologist Craig S. Cary, an assistant professor in UD's College of Earth, Ocean, and Environment, is believed to be the first report of a "eukaryotic metazoan" or higher-order life form capable of surviving sustained, long-term exposure to temperatures up to 176° Fahrenheit (80° Celsius).
Camped on each Pompeii worm's back, hairy-looking bacterial hitchhikers crank out enzymes that may hold the key to new protein-based catalysts for making drugs, paper, food and a host of other goods, according to Cary, lead author of the Nature paper, with Tim Shank of the Institute of Marine and Coastal Sciences at Rutgers State University of New Jersey and Jeff Stein of Diversa Corp., San Diego, Calif.
"Because the Pompeii worm survives such a broad temperature gradient, so too must its bacterial partners," Cary says. "These bacteria may harbor unique eurythermal enzymes, capable of operating over a wide range of temperatures." In addition to their thermal versatility, he notes, eurythermal enzymes can be stored for longer periods of time, compared to conventional enzymes, and they can operate in organic solvents.
Cary's latest findings on Alvinella pompejana (the Pompeii worm) should boost the global search for new "extremophiles" - organisms tough enough to thrive in hot, corrosive, high-pressure environments. The applications for these organisms seem endless. Taq polymerase, for example, an extremophile enzyme discovered in hot springs at Yellowstone National Park, now allows researchers to amplify and analyze tiny bits of the genetic coding material, DNA (deoxyribonucleic acid). Heat-loving enzymes also help dislodge oil inside wells, convert cornstarch to sugar and support a host of other industrial processes by speeding biological and chemical reactions. Because doctors routinely prescribe enzymes such as the clot-buster, streptokinase, Cary says eurythermal enzymes may prove useful for pharmaceutical production, too.
Some Like it Hot
Certain simple, "prokaryotic" organisms grow at temperatures above 235.4°F (113°C), Cary says, but such high heat kills eukaryotes. "The nuclear and mitochondrial membranes in more complex organisms were thought to be their Achilles heel," he explains. "When those membranes melt, it's curtains for the eukaryote."
For most complex organisms, he adds, "131°F [55°C] has been the upper limit." The Sahara Desert ant, Cataglyphis, was long hailed as the most heat-hardy creature on Earth, capable of foraging for brief periods under a blazing midday sun, when temperatures soar to 131°F. Then, French researchers reported spotting a Pompeii worm in water nearly twice as hot (221°F/105°C). But, Cary says, that exposure was fleeting, and the worm was outside its natural environment - the long, hot tubes it calls home.
Enter the Mosquito Probe
To penetrate worm condos beneath the eastern Pacific Ocean, Cary's team used a specially designed device featuring a titanium probe that's six inches long but only three-quarters of a centimeter in diameter. Dubbed "the Mosquito," the probe was deployed by the deep-submergence vehicle Alvin during trips to the Axial Summit Caldera, west of Mexico and south of Baja, Calif. (9° north and 105° west of the equator).
At this site along the East Pacific Rise, the Earth's crustal plates are moving apart, creating hydrothermal vents and geysers that spew a hot, toxic brew of hydrogen sulfide and heavy metals into the sea. Here, the 4-inch-long Pompeii worm, covered with fuzzy bacteria, builds its home. Cary and his colleagues took Alvin close to worm tubes, and the pilot carefully manipulated the Mosquito into a Pompeii worm's 'front door' - an opening just 2 centimeters wide. At a depth of 6 centimeters inside the tube, the probe measured the temperature every 2 minutes, for up to three days. The team also measured the temperature at tube openings.
"The worm's gills, sticking out of the tube, are in water averaging 72° Fahrenheit [22°C], while its posterior end is parked in water that's 176° Fahrenheit [80°C]," Cary says. These readings, Cary says, are unprecedented. "No organism on the planet exists routinely for such a prolonged period of time in such an extreme thermal environment," he adds.
How can the worms stand it? Clearly, Cary says, the tubes don't block much heat, and interior temperatures remain constant, so they're not being flushed by cooler water. In fact, water adjacent to the tube is much hotter, and therefore can't draw heat away from the worms. "It may be that these bacteria are insulating the worms in some way," Cary says. "We don't know yet if this is true, but our data shows that the bacteria thrive at high heat. If the bacteria can stand it, there's good reason to believe that their enzymes can, too."