Yellowstone's Underwater World

EACH year, hundreds of enthralled sightseers pay good money for scenic boat trips on Yellowstone Lake, which at 7,740 feet elevation is the largest high-altitude lake in North America. When Val Klump and Charles Remsen head out onto the water, though, they sit in their research boat's bobbing cabin, its windows shrouded with aluminum foil, and watch television. The two scientists gaze at crystalline pictures of one of the most unusual lake environments in the world, one so convoluted that they call its study ``bio-geo-chemistry.'' Their unprecedented views of this strange realm come from the video camera housed in a small robotic submarine that cruises along the lake floor 300 feet below.

``This is terrific,'' Dr. Remsen says, staring at the video screen. ``Can you turn left a little? Look at those rocks, those miniature grottoes. See the bubbles coming out?''

As the submarine, known as MiniRover and piloted from the command boat, combs the murky lake floor, it comes across vast fields of gurgling thermal vents bubbling and belching hot water and gases. Around these hot spots cluster colorful red-orange sponges that gobble up strange bacteria, which manufacture their energy out of the chemical soup pumped into the icy lake from deep within the earth.

``Everybody knows about Old Faithful and the terrestrial geysers and hot springs here,'' Dr. Klump says. ``But this is a whole new world that no one ever sees; and it's even more incredible and active than what you can see on land.''

During the last seven summers, geochemist Klump and biologist Remsen, funded by the National Undersea Research Program, have been leading scientific teams to probe Yellowstone Lake's surreal depths. The scientists are from the University of Wisconsin's Center for Great Lakes Studies. They want to discover just what contributions the rich hot-water flows make to the lake's unusually high productivity.

For an alpine lake frozen over almost six months of the year, Yellowstone Lake is unexpectedly prolific, supporting a myriad of bacteria and algae diatoms, shrimp-like zooplankton, and native cutthroat trout. Scientists know that the lake is more productive when fertilized with ash from forest fires and during warmer years, but they figure changes in thermal flows could also play a role.

``It's one piece of an incredibly complex puzzle,'' Remsen says. ``Just how big it is and where it fits in, we don't know yet.''

MUCH of Yellowstone National Park with its well-known geysers and boiling springs sits within the rim of a tremendous volcanic crater about 30 miles across that last erupted about 600,000 years ago.

Like the Hawaiian Islands, Yellowstone overlies a hot spot in the earth's crust. Groundwater percolating down through cracks in the rock is heated to above boiling as it nears vast underground reservoirs of molten rock; it then resurfaces to create the park's famous thermal features.

Yellowstone Lake straddles the caldera rim. Outside the crater, the lake floor is unexpectedly flat and boring. Inside, it is topsy-turvy.

Giant cracks and crevices slice across the lake bottom, while shimmering curtains of carbon dioxide bubbles stream up from deep rifts, past tall red cliffs that are criss-crossed with cracks in a brick-like pattern.

Many rocks are unusually bare of mud; and odd depressions that should normally become filled with sediment lead the researchers to think that aquatic geysers periodically rip through the lake bottom, clearing some deposits away.

These features also hint, the scientists say, that the lake may cover one of Yellowstone's most turbulent regions. National Park Service geologist Wayne Hamilton notes that the lake floor plunges to depths of almost 400 feet, closer to the magma boilers buried beneath the park. The floor may also be frequently shifted and cracked by the flurries of tiny earthquakes that constantly rock the region.

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