Anchorage,
Alaska (AP)—Erosion threatens to
topple coastal Alaskan villages. Melting ice threatens polar bears. Now, a
marine scientist says the state's marine waters are turning acidic from
absorbing greenhouse gases faster than tropical waters, potentially endangering
Alaska's $4.6
billion fishing industry.
The same things that make Alaska's marine waters among the most
productive in the world — cold, shallow depths and abundant marine life — make
them the most vulnerable to acidification, said Jeremy Mathis, a chemical
oceanographer at the University of Alaska Fairbanks.
This Feb. 6, 2009, photo provided by the University of Alaska, Fairbanks, School of Fisheries and Ocean Sciences shows Jeremy Mathis right and Kristen Shake, one of his students studying ocean acidification, testing seawater samples in Jeremy's lab on the UAF campus in Fairbanks, Alaska. Alaska's marine waters are turning acidic from absorption of greenhouse gases faster than tropical waters, according to findings by Mathis. (AP Photo/University of Alaska, Fairbanks, School of Fisheries and Ocean Sciences)
"Ecosystems in Alaska
are going to take a hit from ocean acidification," he said. "Right
now, we don't know how they are going to respond."
Alaska has already seen
more than its share of global warming effects: shrinking glaciers, coastal
erosion, the march north of destructive forest beetles formerly held in check
by cold winters, melting Arctic Ocean ice that
also threatens walrus and other marine mammals.
Ocean acidification, the lowering of basicity and the
increase in acidity of marine waters, is tied to increased carbon dioxide
levels in the atmosphere.
Oceans absorb 22 million tons of carbon dioxide from human
activities per day, removing 30 percent emitted to the atmosphere each year and
mitigating the harmful impact of greenhouse gas, according to the Intergovernmental
Oceanographic Commission.
When carbon dioxide dissolves in sea water, it forms
carbonic acid. That decreases the amount of calcium carbonate, used by marine
creatures to construct shells or skeletons.
Mathis last spring collected water in the Gulf
of Alaska and found samples to be more acidic than expected — and
higher than in tropical waters. The results matched his findings in the Chukchi
and Bering seas off Alaska's
west and northwest coast. Cold water absorbs and holds more gas than warm
water, Mathis said.
His research in the Gulf of Alaska
uncovered multiple sites where concentrations of shell-building minerals were
so low, that shellfish, including crab, and other organisms would be unable to
build strong shells.
"We're not saying that crab shells are going to start
dissolving, but these organisms have adapted their physiology to a certain
range of acidity," Mathis said. "Early results have shown that when
some species of crabs and fish are exposed to more acidic water, certain stress
hormones increase and their metabolism slows down.
"If they are spending energy responding to acidity
changes, then that energy is diverted away from growth, foraging and
reproduction."
Acidification could affect the tiny pteropod, also known as
a sea butterfly or swimming sea snail. It is at the base of the food chain and
makes up nearly half of the diet of pink salmon. A 10 percent decrease in
pteropods could mean a 20 percent decrease in an adult salmon's body weight.
"This is a case where we see ocean acidification having
an indirect effect on a commercially viable species by reducing its food
supply," Mathis said.
The shallow waters of Alaska's
broad continental shelves also retain more carbon dioxide because there is less
mixing from deeper ocean waters.
Another contributor is the rich biological life of Alaska waters, from tiny
plankton to humpback whales. All use oxygen and emit CO2. Mathis and other
scientists call it the "biological pump." Phytoplankton, like other
plant life, absorbs CO22 and gives off oxygen, but when it dies and sinks in the
shallow Alaska
waters, decomposes and adds carbon to the water column.
Mathis has been warning fisheries managers around the state
of ocean acidification. He has been hearing back of salmon returns with fewer,
smaller fish reaching streams.
"We can't correlate that yet to ocean acidification or
any climate process," he said. "We cannot make those connections yet
but there's indications in the ecosystem that the ecosystems are
stressed."
He said there should be a twofold course of action:
increasing studies and observation of the effects of ocean acidification, and
reducing carbon emissions.
A future study will look at the physiological impact of
acidification on one of Alaska's
money fish, pollock. A graduate student will rear pollock from hatch and study
them in the larval and juvenile stages under different acidified conditions,
looking for decreases in body mass, increases in stress hormones and other
physiological indicators.
Pollock is the largest U.S. fishery by volume. Annual
catches average 2.5 billion pounds and provide raw material for fish sticks and
fast food fish sandwiches. Ocean acidification could be a blow to commercial
fishing, which accounts for 50 percent of U.S. seafood production.
The Center for Biological Diversity, citing Mathis'
findings, renewed its call for Alaska
to declare its waters impaired under the Clean Water Act. The state last year
rejected the group's first request for the declaration.
SOURCE: The Associated Press
