Lake Hoare Camp,
Antarctica
When the explorer Robert Falcon
Scott discovered the Taylor Valley in 1903, he
called it "a valley of the dead." As he
wrote later in "The Voyage of the
Discovery," the valley's brown hills are
covered with coarse sand strewn with numerous
boulders. There are no plants on its hillsides
and no fish in its lakes. "We have seen no sign
of life," Scott reported, "not even a
moss or lichen."
But while Taylor
Valley hardly teems with life, Scott was wrong to
call it dead. Millions of microscopic plants and
animals live here, hidden in the soil, under the
perenially frozen surfaces of the lakes and even
inside rocks. Researchers who have traveled to
this wilderness think they offer important clues
to life in more conventional earthly ecosystems,
and even to how life might be lived elsewhere in
the solar system.
Nematodes
The top spot on the food chain here
is occupied by microscopic nematode worms,
"the largest land-dwelling creatures in the
Dry Valleys," as Andrew Parsons put it. Mr.
Parsons is a research associate with Dr. Diana H.
Wall, director of the Natural Resource Ecology
Laboratory at Colorado State University and one
of the chief researchers working here. Mr.
Parsons calls Taylor Valley "the simplest
ecosystem on the planet."
The nematode
researchers, dubbed "worm herders" by
the helicopter pilots who ferry them and their
samples, are measuring what factors affect the
abundance and variety of nematodes. Among other
things, they have discovered that when it is too
cold and dry, nematodes enter a state of
suspended animation, called anhydrobiosis, in
which they lose up to 99 percent of the water in
their bodies.
Lake
life under the ice
Other researchers are concentrating
on the unicellular microbes that have learned to
survive in this environment, under the lake's
permanent cover of more than 10 feet of ice.
Despite that obstacle to lush growth, "there
are a lot of creatures here" ... algae that
form mats on the lake bottom
from In an Antarctic Desert,
Signs of Life
-- New York
Times, 2/3/98
The McMurdo Dry
Valleys are located on the western coast of
McMurdo Sound (77°00'S 162°52'E) and form the
largest relatively ice-free area (approximately
4800 square kilometers) on the Antarctic
continent. These ice-free areas of Antarctica
display a sharp contrast to most other ecosystems
in the world, which exist under far more moderate
environmental conditions. The perennially
ice-covered lakes, ephemeral streams and
extensive areas of exposed soil within the
McMurdo Dry Valleys are subject to low
temperatures, limited precipitation and salt
accumulation. Thus, the dry valleys represent a
region where life approaches its environmental
limits...
The dry valleys,
unlike most other ecosystems, are dominated by
microorganisms, mosses, lichens, and relatively
few groups of invertebrates; higher forms of life
are virtually non-existent.
The non-turbulent
nature of the perennially ice-covered lakes in
the dry valleys restricts mixing of nutrients to
diffusion processes. Pelagic lake investigations
are being done to examine organic carbon
transformations between phytoplankton and
bacterioplankton, examine the influence of
nutrient input via streams on phytoplankton
productivity, and determine primary loss rates
for the phytoplankton (e.g., respiration,
sinking).
Lakes within the
McMurdo Dry Valleys support abundant, widespread
growths of benthic cyanobacteria-dominated mats.
The Dry Valley
soils account for the majority of the valley
surface area. ... Globally, there are no other
soil systems where nematodes represent the top of
the food chain and where food webs have such
simple structure. The majority of soils sampled
across the valleys (65%) support up to three
invertebrate taxa (tardigrades, rotifers,
nematodes), but in contrast to other ecosystems,
many soils lack invertebrates.
text and picture
from McMurdo Dry Valleys
Long-Term Ecological Research (LTER)
Nematodes are the
second most common form of life on Earth, after
the arthropods. Previously classified
differently, they now appear to be in the same
category as flatworms and other
"coelomate" worms (see the Origins
page) and appear to have been around since the
Cambrian period - which is to say, one of the
first representatives of Earthian multicellular
life. Given a little water, some bacteria to
eat... these guys could really go for Mars.
Introduction to the
"Aschelminth" Phyla
-- UC Museum
of Paleontology
Roundworms
-- Encarta
Online
Invertebrates
links
-- Electronic Zoo, Division of Comparative
Medicine, Washington University
Wormland
links
-- University of Southampton, UK
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