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. Last Updated: 07/27/2016

Scientists Find Life in Frozen Natural Gas Chunks

WASHINGTON -- Rushing to escape an approaching hurricane, marine biologist Charles Fisher had just surfaced from a dive. A cable had snapped, costing him a big "bush" of 1.8-meter tube worms he was trying to bring aboard his research vessel. Still, baffled crewmates noticed, Fisher was grinning happily.

During that descent last month to the sunless floor of the Gulf of Mexico, 540 meters below the surface and about 94 kilometers south of New Orleans, the Pennsylvania State University researcher had discovered what appears to be a new -- and remarkable -- species of worm living on, and in, mounds of frozen natural gas (mostly methane) that has seeped from beneath the ocean floor.

The discovery of any new species is of interest, researchers say, but to find a fairly complex animal living in such a totally unexpected and bizarre habitat, with what could be a fundamentally new physiology, makes this case especially exciting.

"These worms are the major players in a new and unique marine ecosystem," said Fisher. "These are not just another common worm in the mud."

Fisher and Phil Santos, pilot of the four-person mini-submarine Johnson Sea Link, caught their first glimpse of the flat, pink centipede-like creatures, 2.5 to 5 centimeters long, living in dense colonies on a 1.8-meter ice mound shaped like a mushroom July 15. Some were rowing themselves, like tiny Viking ships, around on the honeycombed yellow and white ice surface, using banks of oar-like appendages that bristle from their sides. They clearly were occupying burrows dug into the mound.

The astonished team returned to their mother ship, hastily reconfigured the little submersible and returned to the ice mound the same day, Fisher recalled. This time, they photographed and captured live worms, which they are studying in shoreside laboratories. They have subsequently found ice worms on other nearby mounds.

The deep ocean bottom has held increasing fascination for scientists since the late 1970s, when the discovery of hydrothermal vents there led to the realization that a vast realm of previously unknown organisms -- sometimes called extremophiles -- manage to thrive in environments once considered hostile, if not impossible, for life. Scientists have found microbes living in scalding hot waters, and freezing subsurface ice, in acid, dirt and rock.

This creature is not a microbe, but an animal. Its exceptional habitat is the peculiar form of ice known as gas hydrate. This crystallized blend of water and natural gas forms in great abundance in the high pressures and low temperatures of the deep sea, but in most regions it remains buried deep in marine sediment. The Gulf of Mexico is one of the few places where lumps of hydrate break through the sea floor. Temperatures are about 7.2 degrees Celsius, almost too warm for methane ice, Fisher said, even with pressures 60 times that at sea level.

Scientists had hypothesized that primitive microbes might live on the ice mounds, but none have been detected. "Certainly no one had even imagined animals living on them," Fisher said. The new species -- not yet named -- is a variety of the common aquatic worms known as polychaetes. "We now know that these higher-order organisms can live right on methane hydrates."

While conditions on the ice mounds are not nearly as extreme as those endured by microbial extremophiles of various types, Fisher said, "On the scale of animal life, this is an extremely weird habitat. ... For an animal, we've got a potentially very toxic environment."

Fisher emphasized that researchers have only begun to study the worms.

If the worms turn out to live on shallow sea floor gas mounds worldwide, Fisher said, "they could have a significant impact on how these deposits are formed, and dissolve ... and on how we go about mining or otherwise harvesting this natural gas as a source of energy."