tube worms illustration
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Uncountable Bacteria
Oceans Under Siege
 
Essentially a giant housing for bacteria, this tube worm grows slowly but steadily on the sea floor in the Gulf of Mexico.

Fisher Lab, Penn State University.


 

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The Johnson-Sea-Link submarine

Courtesy Harbor Branch Oceanographic Institution.
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Want to live forever? Try a cold, dark sulfide tonic

Superannuated annelids
POSTED 10 FEB 2000 Researchers have found stunning evidence that peace and quiet is the prescription for a long, healthy life:

Peace and quiet -- spiced with a high concentration of dissolved sulfides, a dribble of hydrocarbons, and a drizzle of Mississippi mud.

A tube-shaped worm surrounds a sac of bacteria Peace and quiet -- cooked at 6 degrees Celsius with absolutely no light but gazillions of pounds of pressure per square inch.

This scrumptious recipe emerges from new research into tube worms living 1,800 feet beneath the Gulf of Mexico off the Louisiana coast. The worms grow to be more than 2 meters long and are anchored to rocks on the muddy bottom in areas where hydrocarbons naturally seep through the sea floor.

After staining the worms and measuring new growth one year later, the researchers calculated that the creatures live in excess of 170 to 250 years. Among marine animals lacking a spinal column, these live longer than anything except coral and similar colonial animals.

The worms contrast sharply with closely related worms that live near the hot-water ("hydrothermal") vents found elsewhere on the ocean floor. "The hot hydrothermal vents are a much more vigorous, variable and ephemeral environment than the cold hydrocarbon seeps," says Charles Fisher, professor of biology at Penn State University, who directed the cold-seep research. Indeed, the hot-water worms are the fastest-growing organisms on the sea floor, while the cold-water worms are the most venerable. undersea explorer

Sucking gas
Almost as curious as the worm's age is its style of life. Living in absolute darkness, the local ecosystem can't depend on photosynthesis. There's little to "eat" in the conventional sense, so instead of eating, the worm relies on internal bacteria to do its eating.

That curious metabolism explains why the worm is found near hydrocarbon seeps, says Derk Bergquist, a graduate student at Penn who studies them. Deep under the sea bed, a layer of oil-bearing shale is being squeezed, cracking the shale and allowing hydrocarbons from the oil to seep upward.

Before the hydrocarbons reach the seabed, however, they are decomposed by map of the region where tubeworms foundbacteria, releasing byproducts containing only hydrogen and sulfur. The worms gather these sulfur compounds (together with oxygen and carbon dioxide) through a gill-like structure at the top, and possibly through their roots.

The chemicals are delivered by the worm's blood to bacteria which oxidize the sulfur to make sugars that the worm can use -- like a no-limit credit card -- to power its lifestyle. (Want more details?)

Coddling codgers
Johnson-Sea-Link submarine Curiously, the sulfides in the water benefit the worms in a second way. "The poisonous sulfide keeps out predators," Bergquist says. "The worms probably get nipped once in a while by a crab, but they don't have to constantly repair themselves. They don't suffer insults, get bumped or bruised. The environment is not mean to them."

On a more theoretical level, Bergquist says evolution presumably weeded out genes that would cause worms to die young. The worm larvae require rocks to start growing -- they can't get started on the muddy sea floor -- so once they find a rock, they might need to inhabit it for many years. "If there are not a lot of settlement sites, if you have a short lifespan, it may not be possible to get a foothold," Bergquist speculates. "You need to have a long lifespan to ensure representation in the next generation."

Funding for the project came from the federal Minerals Management Service, which wants to ensure that oil drilling does not endanger the worms. A big deepwater drilling rig is only 1,500 feet from a cluster of worms.

In addition to figuring out whether drilling can be done safely, the Penn State group wants to get more information on a second species of tube worms living at the cold seeps. The examination of life in the rare ecosystems that are independent of photosynthesis is sure to yield more surprises.

One can only hope, for example, that they will find a tastier recipe for longevity than cold salt water laced with poisonous sulfides. Any votes for water aerobics and lights-out stress reduction?


-- David Tenenbaum deep sea diver

 
BIBLIOGRAPHY
Longevity Record for Deep-Sea Invertebrates, Derk Bergquist et al, Nature, pp. 499-500, Feb. 2, 2000.

 
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