Antarctic Desert Rich With Insights Into Life on the Edge
for National Geographic News
|February 26, 2003|
When British polar explorer Robert F. Scott discovered Antarctica's Taylor Valley in 1903 he described it as a "valley of the dead."
"We have seen no living thing, not even a moss or a lichen," he wrote in The Voyage of the Discovery, his book about the journey.
The valley is part of the McMurdo Dry Valleys, a cold, barren desert comprising 1,853 square miles (4,800 square kilometers) in southeastern Antarctica. It is the frozen continent's largest ice-free area and has become a focal point of scientific research in the 100 years since its discovery.
Contrary to Scott's 1903 observation, researchers have found that an ecosystem thrives in the soils, under the surface of frozen lakes, and even inside rocks. Nematodes, or worms, are the top predators.
"In the streams you have mosses and algal mats. In lakes you have phytoplankton and benthic algal mats, and the soils contain nematodes and other critters like rotifers and tardigrades," said Andrew Fountain, a geologist at Oregon's Portland State University.
Fountain is one of several scientists who regularly visit the dry valleys to study this life, trying to understand how it can survive in such a harsh environment.
"The dry valleys are an end member ecosystem. They provide us with an example of how an ecosystemthe organisms and the physical environment that supports themcan function on the edge of survivable conditions," said Peter Doran, an earth scientist at the University of Chicago in Illinois.
Doran, like Fountain and many other scientists, regularly visits the dry valleys as part of the National Science Foundation's McMurdo Long Term Ecological Research (LTER) program. There are 24 LTER sites spread around the world, allowing scientists to study ecological processes over long time scales. The dry valleys were added to the network in 1993.
100 Years of Same
John Priscu, an environmental scientist at Montana State University in Bozeman who has conducted research in Antarctica since the early 1980s, said the McMurdo Dry Valleys are "one of the oldest landscapes on the planet."
The Transantarctic Mountains block the seaward flow of the East Antarctic Ice Sheet from covering the region. Glaciers that grow from the surrounding mountains do not accumulate enough snow to fill the valleys with ice.
Researchers say that while lake levels have risen about 33 feet (10 meters) since Scott first set foot in the valleys 100 years ago and glaciers have shifted, the region has looked pretty much the same for the past 3 million years.
What has changed, however, is the amount of people visiting the dry valleys and the technology they bring with them, said Doran. Hundreds of scientists now come to the valleys to conduct research each year. They bring with them computers, cell phones, and other high-tech laboratory equipment.
"Scientists in the field camps in Taylor Valley can surf the web, do e-mail, and call the U.S. like they were using any phone in Washington State. The satellite connection is there, and that's what shows up on your phone bill," he said.
In fact, Doran said that when he and his colleagues broke a stunt kite that they flew during their free time, they called a toll-free 800 number and three weeks later had a replacement part delivered to them.
The sheer volume of scientists coming to the McMurdo Dry Valleys to conduct research is creating an impressive body of work about life on the edge, said Fountain. The McMurdo LTER program was given a six year extension in 1998 to build on the discoveries being made about the region.
Key among the finds is the discovery that the current structure of the ecological community is based on climate changes that took place thousands of years ago. "The current ecosystem depends in a very direct way on the legacy of past climatic effects," said Fountain.
For example, researchers have determined that about 40,000 years ago the Ross Ice Shelf advanced and blocked the Taylor Valley's opening to the ocean. A huge lake subsequently filled the valley and algal mats formed at the lake bottom. About 8,000 years ago, the Ross Ice Shelf retracted and the lake drained out, leaving the algal mats behind.
"Today, that relic algal mat is thought to be the major carbon source for the soil ecosystems," said Fountain. "The spatial dimensions of the abundance and diversity of the soil invertebrates is partly determined on this relic carbon source."
An impressive discovery on Priscu's list is the recent finding that despite temperature rises around the planet, the McMurdo Dry Valleys have actually cooled off slightly in the past 35 years.
The scientists are not sure of the reasons behind the cooling, but suspect it may be related to the disappearance of a wind pattern, called the katabatic wind, that flows over glaciers and dumps warm clouds into the valleys.
"It sounds strange, but windy, cloudy days are warm, and brilliant sunny days are cold," said Priscu.
Other research highlights include finding microbes living under six feet (two meters) of lake ice. For 10 years Priscu and his colleagues kept hitting sediments halfway through the ice when drilling for core samples. They cursed it for dulling drilling bits. Then, in 1998, they discovered the dirt contained a whole microbial community.
"We are finding novel microbes all over the place" he said. Such discoveries will help scientists understand how life evolved on Earth and what kind of life might exist on other planets.
"For instance, if Mars was a warmer and wetter planet in the past, the dry valleys may represent a close analog to the last ecosystems on Mars as the temperature dropped," said Doran.
Researchers plan to continue to study McMurdo Dry Valleys for years to come, discovering what makes life tick in one of the harshest environments on Earth.
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