Warming linked to 'unprecedented' algae growth in Arctic lake
Pastor Dale Morgan
Warming linked to 'unprecedented' algae growth in Arctic lake*
MONTREAL, Sept 26 (AFP) Sep 27, 2007
Global warming is believed to be softening the harsh Arctic environment,
causing the algae population in Canada's northernmost lake to spike over
the past two centuries, researchers said Wednesday.
The team, led by Laval University scientists Warwick Vincent and
Reinhard Pienitz, found aquatic life in Ward Hunt Lake, located on
island north of Ellesmere Island, increased 500-fold during the period.
The changes occurred at a speed and range "unprecedented in the lake's
last 8,000 years," the researchers said in a statement.
And, they say, the likely culprit is "climate change related to human
activity."
The findings, to appear in the journal Geophysical Research Letters on
September 28, are based on an analysis of an 18-centimeter (seven-inch)
sediment core plucked from the lake's center in August 2003.
Its layers, the researchers said, chronicle the diversity and abundance
of aquatic life in the lake over the last 8,450 years.
The deepest layers of sediment revealed a very small number of algae as
well as only minor variations in concentration, but the top two
centimeters (0.8 inches), corresponding to the last 200 years, showed an
abrupt increase in the lake's algae population, they said.
"This is of course an extreme environment for living organisms," said
lead author Dermot Antoniades of the Center for Northern Studies.
"But our data indicate that current conditions make the lake a more
favorable location for algae growth than it was in the past."
"We cannot claim with certainty that these changes were brought on by
human activity, but natural variations observed over the last millennia
were never so abrupt and extensive," he said.
Located on the 83rd parallel in the Quttinirpaaq (meaning "top of the
world" in Inuktitut) National Park, Ward Hunt Island is completely
surrounded by ice.
The lake itself is permanently covered by a four-meter layer of ice,
except for a small peripheral zone that thaws out during a few weeks
every summer.
It was previously believed to be frozen solid year-round.
"We now estimate that in the past two hundred years the ice on the
peripheral has thawed more, permitting organisms to thrive," said
Reinhard Pienitz.
"It seems that the lake is at a critical threshold," he told AFP.
"Suddenly, there's aquatic life in an ecosystem that was once sealed."
According to the UN's Intergovernmental Panel on Climate Change, average
temperatures in the Arctic increased twice as fast as elsewhere over the
past century, and polar ice is expected to be greatly reduced by 2100.