Shifting spring:
Arctic plankton blooming up to
50 days earlier now
--------------------------
The Washington Post March 6,
2011
http://www.washingtonpost.com/wp-dyn/content/article/
2011/03/06/AR2011030602931.html
Shifting spring: Arctic
plankton blooming up to 50
days earlier now
By Brian Vastag
Washington Post Staff
Writer
Climate researchers have
long warned that the Arctic is
particularly
vulnerable to global
warming. The dramatic
shrinking of sea ice in
areas circling the North
Pole highlights those
concerns.
A new report finds that the
disappearing ice has
apparently triggered
another dramatic event -
one that could disrupt the
entire ecosystem
of fish, shellfish, birds,
and marine mammals that thrive
in the
harsh northern climate.
Each summer, an explosion
of tiny ocean-dwelling plants
and algae,
called phytoplankton,
anchors the Arctic food
web.
But these vital annual
blooms of phytoplankton are
now peaking up to
50 days earlier than they
did just 14 years ago,
satellite data show.
"The ice is retreating
earlier in the Arctic, and the
phytoplankton
blooms are also starting
earlier," said study leader
Mati Kahru, an
oceanographer at the
Scripps Institution of
Oceanography in San Diego.
Drawing on observations
from three American and
European climate
satellites, Kahru and his
international team studied
worldwide
phytoplankton blooms from
1997 through 2009. The
satellites can spot
the blooms by their color,
as billions of the tiny
organisms turn
huge swaths of the ocean
green for a week or two.
The blooms peaked earlier
and earlier in 11 percent of
the areas
where Kahru's team was able
to collect good data. Kahru
said the
impacted zones cover
roughly 1 million square
kilometers, including
portions of the Foxe Basin
and the Baffin Sea, which
belong to
Canada, and the Kara Sea
north of Russia.
In the late 1990s,
phytoplankton blooms in these
areas hit their peak
in September, only after a
summer's worth of relative
warmth had
melted the edges of the
polar ice cap. But by 2009 the
blooms' peaks
had shifted to early
July.
"The trend is obvious and
significant, and in my mind
there is no
doubt it is related to the
retreat of the ice," said
Kahru, who
published the work in the
journal Global Change
Biology.
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"A 50-day shift is a big
shift," said plankton
researcher Michael
Behrenfeld of Oregon State
University, who was not
involved in the
study. "As the planet
warms, the threat is that
these changes seen
closer to land may spread
across the entire Arctic."
Ecologists worry that the
early blooms could unravel the
region's
ecosystem and "lead to
crashes of the food web," said
William
Sydeman, who studies ocean
ecology as president of the
nonprofit
Farallon Institute in
Petaluma, Calif.
When phytoplankton explode
in population during the
blooms, tiny
animals called zooplankton
- which include krill and
other small
crustaceans - likewise
expand in number as they
harvest the
phytoplankton. Fish,
shellfish and whales feed on
the zooplankton,
seabirds snatch the fish
and shellfish, and polar bears
and seals
subsist on those
species.
The timing of this
sequential harvest is
programmed into the
reproductive cycles of many
animals, Sydeman said. "It's
all about
when food is available." So
the disrupted phytoplankton
blooms could
"have cascading effects up
the food web all the way to
marine
mammals."
But the Arctic food web is
poorly studied, and so any
resulting
decline in fish, seabirds
and mammals will be difficult
to spot.
As the Arctic Ocean north
becomes less and less icy,
commercial
fisherman have begun eyeing
these vast, untapped waters as
an adjunct
to the famously rich
fishing grounds of the
subarctic Bering Sea,
west of Alaska.
But in 2009, the U.S. body
overseeing fishing in the
region, the
North Pacific Fishery
Management Council, banned
commercial fishing
in the Arctic Ocean, citing
a lack of knowledge about how
many - or
even what kind - of fish
live there.
"There are no catches
authorized because we don't
know enough about
the fish populations there
to set a quota," said Julie
Speegle, a
spokeswoman for the Alaska
office of the National Marine
Fisheries
Service.
Last week, that service
reported results from the
first fish survey
in 30 years of the Beaufort
Sea, an arm of the Arctic
Ocean north of
Alaska. The survey found
sizeable populations of
several commercially
valuable species, including
pollock, Pacific cod, and snow
crab.
How these populations will
respond to the ever-earlier
plankton
blooms is a big unknown,
Sydeman said. But other
research has shown
that northern Atlantic cod
populations crash when
plankton blooms in
that region shift in
time.
Last week, the National
Snow and Ice Data Center, in
Boulder, Colo.,
reported that in February,
Arctic sea ice covered a
smaller area than
ever seen in that month,
tying with February 2005 as
the most
ice-free February since
satellites began tracking
Arctic ice in 1979.
The annual average Arctic
sea ice coverage has decreased
about 12
percent since then, a trend
that appears to be
accelerating, said
Walt Meier, a research
scientist at the center.
Summer ice coverage
has declined even more
dramatically, he said, with
the Arctic losing
almost a third of its
late-summer ice over the past
30 years.
