“It’s like going back to early Earth.” —DAWN SUMNER
Penguin declines
may hinge on krill
By Daniel Strain
Disruptions in the food supply, caused
in part by warming climate, may be to
blame for shrinking populations of Adélie
and chinstrap penguins across the West
Antarctic Peninsula. The penguins’
recent struggles primarily stem from
having too few krill to eat, researchers
report online April 11 in the Proceedings
of the National Academy of Sciences.
In the early 1990s, study coauthor
Wayne Trivelpiece and his colleagues
argued that shrinking ice masses
might hurt icebound Adélie penguins
(Pygoscelis adeliae), while the more
Adélie and gentoo penguins hobnob on
a beach in the South Shetland Islands.
As krill numbers drop in the Scotia Sea,
Adélies may be going hungry.
University in New Brunswick, N.J. Marine
crustaceans gorge on tiny photosynthesizing organisms called phytoplankton,
and Schofield’s research hints that climate change in the West Antarctic Peninsula may be similarly knocking out this
crucial bottom rung of the food chain.
Frigid lake holds analog of early life
Antarctic bacterial colonies look like some of the first fossils
By Alexandra Witze
In the eerie bluish-purple
depths of an Antarctic lake,
scientists have discovered
otherworldly mounds that tell
tales of the planet’s early days.
Bacteria slowly built the
mounds, known as stromatolites, layer by layer on the lake
bottom. The lumps, which
look like oversized traffic
cones, resemble similar fossil structures from billions of
years ago that are considered one of the
oldest widespread records of ancient life.
The Antarctic discovery could thus help
scientists better understand the conditions under which primitive life-forms
thrived. “It’s like going back to early
Earth,” says Dawn Sumner, a geobiolo-gist at the University of California, Davis.
Soft blue light suffuses the otherworldly bottom
of Lake Untersee, Antarctica, where scientists
have found odd structures (purple lumps) built
by layer upon layer of growing microbes.
Sumner and her colleagues, led by Dale
Andersen of the SETI Institute in Mountain View, Calif., describe the discovery
in an upcoming issue of Geobiology.
Researchers study fossil stromatolites, from 3 billion years ago or more,
to understand how life got a foothold on
Earth. Today, stromatolites actively form
in only a few spots in the ocean and in
some freshwater environments, including a few of Antarctica’s other freshwater
lakes. But scientists have never seen any
the size and shape of Lake Untersee’s. “It
totally blew us away,” Andersen says.
“We had never seen anything like that.”
Samples from one mound showed it
was made mostly of long, stringy cyanobacteria, ancient photosynthesizers. The
bacteria may take decades to build each
layer in Untersee’s frigid waters, Sumner
says, so the mounds may have taken thousands of years to accumulate.
Andersen’s team recently studied two
other ice-covered Antarctic lakes, Vanda
and Joyce, without finding large conical
stromatolites there. Understanding what
makes Untersee different would help
scientists better figure out the limits on
life, both today and in the long-distant
past. “It’s a real challenge to our understanding of how these communities
developed,” says Ian Hawes, a polar limnologist at the University of Canterbury
in Christchurch, New Zealand.
FROM TOP: SUE AND WAYNE TRIVELPIECE; D. ANDERSEN
www.sciencenews.org
