Life blooms on floor of deep Siberian lake.

Life blooms on floor of deep Siberian lake

A joint U.S.-Soviet research team has discovered an oasis of life around springs of heated water along the floor of Siberia's Lake Baikal, the oldest and deepest lake on Earth. Many similar "hydrothermal vent communities" thrive in the oceans, but until now scientists had never seen an example in fresh water.

Expedition members discovered the field of vents at a depth of 1,350 feet in the northern section of the 395-mile-long, crescent-shaped lake, which sits just north of Mongolia. Using a submersible to explore the field, researchers photographed a rich community of sponges, bacterial mats, snails, fish and transparent shrimp, some apparently representing unknown species, says chief-scientist Kathleen Crane from Columbia University's Lamont-Doherty Geological Observatory in Palisades, N.Y. Fluids spewed from the vents measured at least 24[degrees]F warmer than the normally frigid bottom water.

The discovery suprised some researchers because measurements made during an expedition two years ago showed no signs that the lake harbored vents, says geochemist Ray F. Weiss of the Scripps Institution of Oceanography in La Jolla, Calif. "I was skeptical that they would find any vents at all," he told SCIENCE NEWS. The recent vent search, conducted during six weeks in June and July, concentrated on a virtually unexplored section of the lake.

Organisms living near hydrothermal vents in the ocean have attracted considerable attention over the last 13 years. While almost all biological communities on Earth derive their primary energy from sunlight through photosynthesis, oceanic vent communities rely on a process called chemosynthesis, drawing their basic energy from chemical nutrients in the warm fluids.

Biologists now seek to determine whether chemosynthesis supports the Baikal communities, says Barbara Hecker of Lamont-Doherty, who has studied photographs from the recent expedition. Researchers will also examine the Baikal organisms to see what characteristics they share with those from ocean vents. Such comparisons could offer insight into the evolution of vent communities.

Whereas most large lakes date back only 10,000 to 20,000 years, Lake Baikal formed about 25 million years ago. Due to its great depth, it holds about 20 percent of the world's supply of liquid fresh water.

The vents found at the bottom of the lake indicate that previous studies have significantly underestimated the amount of heat flowing oiut of the Earth's crust in the Baikal region, says geoscientist Marcia K. McNutt of the Massachusetts Institute of Technology in Cambridge. Future studies of the vents and local heat flow, she says, will yield more accurate estimates and should help geoscientists resolve a debate about why the Asian continent is splitting along the giant rift that created the deep lake. Many researchers view the rifting as a passive process driven by tectonic stress from the distant collision between India and Asia. But some think the Baikal rift results from a more active process, in which hot material rising from Earth's mantle forces the Asian plate to crack apart.