NOAA 2004-046
Contact: Fred Gorell

NOAA News Releases 2004
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Liquid Co2, Rare Mix of Chemical, Sunlight-based Life

Scientists marveled at views of liquid carbon dioxide rising from the seafloor like champagne bubbles as well as the mingling of chemosynthetic and photosynthetic organisms during a recent voyage to the submarine volcanoes in the western Pacific. These discoveries and more were made and filmed on the first direct observation of an active underwater volcano spewing rocks and molten sulfur.

“Submarine Ring of Fire--2004,” the 21-day voyage of discovery was sponsored by the National Oceanic and Atmospheric Administration and by the Natural Sciences and Engineering Research Council of Canada. NOAA is an agency of the Department of Commerce. The expedition concluded April 18.

“This was truly a path finding expedition,” said Capt. Craig McLean, director of NOAA’s ocean exploration program. “The expedition supported NOAA’s mission of ocean exploration for the purpose of discovery and the advancement of knowledge. The team discovered answers to some questions, but raised many more questions that scientists will answer in missions to come. The expedition also underscored the fact that we have much to learn about one of the Earth’s most important features – our oceans.”

The mission joined 34 top scientists from the U.S., Canada, Japan and New Zealand to explore submerged volcanoes of the Mariana arc, an area extending northward from Guam for nearly 760 miles. The science team initially mapped the area in 2003 and discovered 10 hydrothermally active volcanoes.

“Our primary interest in studying these volcanoes is their relatively shallow depth,” said Bob Embley, the mission’s chief scientist and an oceanographer with NOAA’s Pacific Marine Environmental Laboratory. “In contrast to the great depths of most of the mid-ocean ridge volcanoes, these volcanoes commonly rise into the upper reaches of the oceans where most marine life is concentrated and where exchanges in gases take place with the atmosphere.”

The mission relied heavily on the unmanned submersible Remotely Operated Platform for Ocean Science (ROPOS) to probe the depths down to more than a mile where human exploration is limited. ROPOS was launched and guided from the University of Washington Research Vessel (R/V) Thomas G. Thompson. Scientists made 14 dives with the submersible on seven volcanoes and collected hundreds of samples for geological, biological and chemical studies.

“We were just going from one incredible event to the next, seeing things we had never witnessed before,“ said Bill Chadwick, a volcanologist with the Cooperative Institute for Marine Resources Studies at Oregon State University. “It was exciting and quite remarkable in that every volcano we visited was unique.”

A dramatic discovery was made at the first site visited. The unmanned submersible ROPOS and its cameras were 1,800 feet deep on the rim of a crater near the top of a volcano when huge yellow clouds of sulfur-rich effluent enveloped the submersible.

“We aptly named this site ‘Brimstone Pit,’ and when rocks emerged from the cloud hitting the ROPOS, we realized we were the first to witness a deep-sea volcano during an eruptive episode,” Embley said. “It was fortunate we were there to observe and sample it, but it was difficult to take samples in the volcanic crater because of the danger to the ROPOS.

NOAA scientist Dave Butterfield, chemist in charge of water sampling, determined that the fluid was very corrosive, with a high concentration of sulfuric acid. The ROPOS operator on the research vessel sent a signal down the long tether line, commanding ROPOS to reverse engines.

At another site, a spectacular, highly concentrated flow of carbon dioxide-rich fluid was discovered. The science team was astonished to see large bubbles floating up from the seafloor around this site when it was disturbed. After discussion, the consensus opinion was that the bubbles were predominantly liquid carbon dioxide. This is a key discovery not simply for the novelty of the phenomenon.

“We found a natural laboratory where the effects of carbon dioxide on marine organisms can be studied,” said Steve Hammond, chief scientist for NOAA’s Office of Ocean Exploration. The liquid form of carbon dioxide is present due to the great depth, and resulting pressure at the site. At 5,263 feet (approximately one mile), the pressure from the water column is equal to 160 atmospheres.

NOAA scientist John Lupton, the principle investigator studying the gases, teamed with others to collect the bubbles in an inverted plastic tube normally used for taking sediment samples. Some bubbles were then drawn into a special gas-tight titanium bottle.

Hydrothermal activity on submarine volcanoes also fed large populations of microbes specially adapted to use iron, hydrogen sulfide and other chemicals for their energy source. In some areas, the seafloor was covered with a thick reddish-orange microbial “mat” produced by such microbes. Since iron is a limiting element in the surface productivity of the ocean, the hydrothermal output of iron out of such shallow submarine volcanoes is of particular interest.

Biologists found a wealth of new discoveries at the East Diamante volcano in the Mariana Arc. Although this volcano has not erupted for many hundred years, there was extensive hydrothermal activity on the youngest volcanic cones in the center of a six-mile caldera. Scientists observed the rare convergence of the photosynthetic zone, where all life depends on sunlight, and the chemosynthetic zone, where energy is mostly derived from chemicals such as hydrogen sulfide released from reactions between hot seawater and volcanic rocks.

ROPOS climbed a slope covered with a fine white microbial mat feeding off gases from the hydrothermal activity. At 650 feet below the surface, the first photosynthetic green and red algae appeared beneath the white bacterial growth. At 550 feet, ROPOS reached the top of the cone where photosynthetic life dominated. Coral and large basket stars abounded, and schools of multi-hued tropical fish swarmed around the peak.

NOAA is dedicated to enhancing economic security and national safety through the prediction and research of weather and climate-related events and providing environmental stewardship of our nation’s coastal and marine resources.

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