Scientists Return to Galápagos Sea Vents

By Bijal P. Trivedi
National Geographic Today
May 29, 2002

Twenty-five years ago, the discovery of deep sea hydrothermal vents, one and a half miles below the ocean surface, near the Galápagos Islands revolutionized biology and captivated the world with pictures of thriving ocean floor gardens covered with towering, red-plumed tube worms, giant clams and ghostly white crabs.

To mark the silver anniversary, this week a team of biologists and geologists is revisiting the Galápagos Rift to compare the current inhabitants with those documented in previous years. They will also explore neighboring waters 200 miles west of the site for "high-temperature black smokers"—dramatic geological forms that shoot super-heated, inky black plumes of water out of the ocean bed and may have nurtured the first life on Earth.

Life Around the Vents

"The western site, which we believe may be home to black smokers, may host a whole collection of new life-forms that we have never seen," said Stephen Hammond, a geologist and chief scientist for the National Oceanic and Atmospheric Administration's Office of Ocean Exploration. "Who knows what we'll find?"

The unexpected discovery 25 years ago of abundant life in the freezing, pitch-black waters of the deep ocean dramatically changed how we think about the requirements for life, said Jim Yoder, director of the Division of Ocean Sciences at the National Science Foundation. "Here was an entire food web that depended on chemical energy from the earth rather than energy from the sun." Yoder said that this is one of the most significant discoveries in oceanography in the last 50 years.

Vents occur where there is volcanic activity. The cracks in the seafloor allow water to percolate through the ocean crust where it is heated by nearby chambers of magma. The super hot water—sometimes 750ºF (400ºC)—dissolves metals and salts as it travels through rocks, eventually rising and gushing out of the hydrothermal vents. These searing vent cocktails are responsible for the chemistry of the world's oceans.

Among the bouquet of chemicals pouring out of the vents is hydrogen sulfide—a poisonous gas which is toxic to most land-based life. But to the creatures living around the vents, hydrogen sulfide is the source of life. Some bacteria, never seen before the discovery of the vents, use the gas for an energy source. These bacteria are the base of the food chain—crabs, clams and tube worms—and all other vent creatures depend on these microbes for life.

Scientists believe that these vent systems were common 3.85 billion years ago, when the earliest life-forms are thought to have emerged. Possibly the hydrogen-sulfide-eating bacteria near the vents today may resemble these earliest life-forms.

Since the Galápagos vents were discovered in 1977, hundreds of other vents have been identified in oceans around the world. But the inaccessibility of these sites and the hostile conditions of the vent environments mean that scientists still don't have a firm understanding of how life changes in these places, said Tim Shank, a biologist at the Woods Hole Oceanographic Institution (WHOI) and co-chief of the expedition. "We don't even know how long the vents remain active," Shank said.

Looking for the Rose Garden

The current expedition will seek out a 0.6-acre (.24-hectare) plot of red-plumed white tube worms called the "Rose Garden," which is fed by nutrients from hydrothermal vents. The site was meticulously mapped in 1985, and was studied extensively until 1990. And now scientists now want to see whether the garden's inhabitants have changed and whether the vents feeding the area are still active.

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