Science Daily —
Analyses conducted by researchers from Université Laval's Center for
Northern Studies reveal that the continent's northernmost lake is
affected by climate change.

Ward
Hunt Lake in Northern Canada. The top two centimeters of core samples,
which correspond to the last 200 years, showed abrupt changes in the
lake's algae population. (Credit: Dermot Antoniades, Université Laval)

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In an article to be published in
the September 28 edition of Geophysical Research Letters, the
international research team led by Université Laval scientists Warwick
Vincent and Reinhard Pienitz reports that aquatic life in Ward Hunt
Lake, a body of water located on a small island north of Ellesmere
Island in the Canadian Arctic, has undergone major transformations
within the last two centuries.

The speed and range of these
transformations--unprecedented in the lake's last 8,000 years--suggest
that climate change related to human activity could be at the source of
this phenomenon.

The researchers' conclusions are based on the
analysis of a sediment core extracted in the center of Ward Hunt Lake
in August 2003. This 18 centimeter long sediment core containing algae
pigments and diatom remnants was used by the researchers as a
biological archive in order to determine the diversity and abundance of
aquatic life-forms in the lake over the last 8,450 years.

Analysis
of the deepest layers of sediment revealed a very small number of algae
as well as only minor variations in concentration. However, the top two
centimeters of the core, which correspond to the last 200 years, showed
abrupt changes in the lake's algae population: during that period,
chlorophyll a concentration, a pigment found in every species in the
lake, increased by a factor of 500.

A type of diatom typical of
very cold environments also made its first appearance during the same
period. "The absence of diatoms and the low pigment concentration below
the top 2.5 centimeters of the core suggest that the lake was
permanently frozen in the past," explains lead author and Center for
Northern Studies researcher Dermot Antoniades.

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 4-meter layer of ice,
except for a small peripheral zone that thaws out during a few weeks
every summer.

"This is of course an extreme environment for
living organisms, but our data indicate that current conditions make
the lake a more favorable location for algae growth than it was in the
past," points out Antoniades. "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,"
concludes the researcher.

In addition to Antoniades, Vincent, and
Pienitz, the article is co-authored by Catherine Crawley from the
University of Toronto, Marianne Douglas from the University of Alberta,
Dale Andersen from the Center for the Study of Life in the Universe
(USA), Peter Doran at the University of Illinois in Chicago (USA), Ian
Hawes from the National Institute of Water and Atmospheric Research
(New Zealand), and Wayne Pollard from McGill University.

This
study was conducted as part of the ArcticNet program, which brings
together scientists and managers in the natural, human health and
social sciences with their partners in Inuit organizations, northern
communities, federal and provincial agencies and the private sector to
study the impacts of climate change in the coastal Canadian Arctic.

Note: This story has been adapted from material provided by Université Laval.