Sea floor observatory set up at volcano

September 21, 1998
Webposted at 4:20 PM EDT

By Environmental News Network staff

Many scientists now believe that life may have begun first at deep-sea hydrothermal vents.

(ENN) -- Tubeworms living in 360 degree Celsius water, snow-blower vents, hydrothermal vents harboring what may be the oldest life form on Earth; these are a few of the things a team of oceanographers were looking for -- and found -- in their quest to establish a sea floor observatory at the Axial Volcano.

The NeMO 1998 expedition left aboard the NOAA research ship Ronald H. Brown Aug. 24 and returned Sept. 20. The ship was loaded with a multitude of sampling, sensing and photographic instruments, some of which are being left behind at the summit of the Axial Volcano, 240 miles off the coast of Oregon, to continue their work for the next year. The Canadian-built remote operating vehicle known as ROPOS -- Remotely Operated Platform for Ocean Science -- was also on board, destined to take more than 20 unmanned dives in the pursuit of science.

"The instrument systems we put in place will be the beginning of a totally unique, long-term, unmanned observatory on the sea floor that we are calling 'NeMO,' short for New Millennium Observatory," said Stephen Hammond, director of NOAA's Vents Program in Newport, Ore., which is leading the expedition.

"NeMO will make it possible to begin understanding relationships between volcanic and hydrothermal hot springs and the microbial biosphere which lies beneath the volcano's surface."

The NeMO expedition is a follow up to several earlier scientific visits to the underwater volcano. A swarm of more than 8,000 earthquakes on Axial Volcano was detected in January 1998 using a U.S. Navy array of underwater hydrophones. Earthquake swarms are associated with the onset of a deep volcanic eruption. Scientists from NOAA quickly put together a response team to study the event in its initial stages when its effects on the ocean's chemical, thermal and biological environments would be most extreme.

The ship was loaded with the Canadian-built remote operating vehicle known as ROVOS, and a multitude of other sampling, sensing and photographic equipment and instruments.

Scientists on these early cruises to the site, using the submersible Alvin, discovered widespread, intense plumes of hot water flowing from new sea floor fractures. These hydrothermal vents are oases for unique life forms known as thermophiles, which are sometimes living in water that has reached a temperature of 360 degrees Celsius. The microbes are apparently one of the most ancient forms of life known on Earth. In fact, many scientists now believe that life may have begun first at deep-sea hydrothermal vents.

Scientists have only recently discovered that Earth hosts a subsurface biosphere of microbial life, and have very limited understanding of its nature and extent. They do know that the subsurface biosphere is restimulated during volcanic eruptions and microorganisms and their products normally residing at depth are brought up to the surface and can be sampled around hydrothermal vents.

NeMO98 is designed to expand our understanding of this biosphere and scientists representing geology, chemistry, biology, oceanography, geophysics are part of the NeMO team. Each dive requires a tremendous amount of planning since not all the scientific instruments can fit onto the ROPOS at the same time. More than 20 dives were made during the ship's time at sea.

Unlike manned submersibles, the ROPOS can stay down for extended periods of time. Its first dive served mainly as a reconnaissance dive and totaled 25 hours of bottom time. It took a look around and located markers that the submarine Alvin had deployed in mid-July. Several additional vent sites (including some "snow-blower" vents that spew out bacterial floc) were found and markers were put at the best ones for taking water and biological samples on later dives.

These tubeworms apparently died when they were cut off from their source of sulfide-rich vent fluid.

The ROPOS team also looked on the first dive for a large field of tube worms that was first seen in July 1997. It was never found, and scientists involved in that particular study became convinced that the field had been completely covered with new lava and obliterated without a trace -- a Pompeii of the underwater world. Many of the tubeworms' close neighbors narrowly escaped being barbecued by the flowing lava.

On subsequent dives, scientists collected biological and basalt samples and deployed bacterial traps. A missing rumbleometer -- an instrument package that had been deployed during the summer of 1997 but wasn't responding the way it should, was also found; stuck in lava. Attempts to free it were futile.

NeMO scientists looking for lava from the January 1998 eruption came up with a new discovery. Lava from other eruption sites has always been black, shiny and sediment-free. The lava at Axial was covered almost everywhere with an orange, slimey-looking deposit. Eventually it was determined that it came from bacterial growth that forms directly on the new lava as it cools. This is the first time the coating on a new flow has been seen, and samples were taken.

ROPOS also located a sulfide chimney (formed by mineral deposits around a high-temperature "smoker" vent) that had been photographed in 1996. The chimney was still actively venting hot water, and had lots of tubeworms growing around it.

"Every dive has brought fresh insights about the extraordinary effects of the eruption on the summit of Axial Volcano," Robert Embley, the expedition's chief scientist, wrote in his shipboard log. "The rise of hot magma up to and onto the seafloor generated an extraordinary new hydrothermal system that stimulated an extensive shallow-subsurface microbial bloom that is still ongoing. Growing around small holes in the lava where warm vent fluid was emerging were pockets of tiny tubeworms, representing the first stage in the recruitment of these ubiquitous vent fauna. The sample taken at that site will probably be one of the most important biological samples taken during NeMO98."

Earthquake activity also has apparently had an effect on the biological communities. At one site (originally visited in the late 1980s) a colony of dead tubeworms was found attached to the top of a lava spire that had toppled. Apparently the tubeworms died when they were cut off from their source of sulfide-rich vent fluid.

The expedition was organized and supported by NOAA's Vents Program, National Sea Grant College Program, and National Undersea Research Program. It is the first in a multi-year series of expeditions planned to the NeMO site.

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