Fossil Fuel Use Threatens Marine Ecosystems

from the SuwanneeRiverTimes_eNews
(The Oregonian)

Fossil fuels threatening sea life, researchers say
Pollution - Acid levels from carbon dioxide are rising in the
Pacific, impeding shell formation

by Michael Milstein
The Oregonian

Scientists just back from a research cruise across the northern
Pacific say the ocean has soaked up so much carbon dioxide from
human burning of fossil fuels that it's turning more acidic,
disrupting growth of coral and the tiny sea creatures salmon and
other fish rely on for food.

The chemical signature of the carbon dioxide makes clear it is from
human and not natural sources, said Richard Feely, an oceanographer
with the federal Pacific Marine Environmental Laboratory in Seattle
and chief scientist for the cruise.

Carbon dioxide is known as a greenhouse gas that contributes to
global warming by trapping heat in the atmosphere. Oceans help
offset that effect by absorbing about a third of the carbon dioxide
produced by humans, the researchers said.

But the new findings reveal that all the carbon dioxide is changing
the delicate chemical balance of ocean water that lets coral,
shellfish and forms of tiny plankton construct their vital shells.

The tiny life forms play vital parts in marine ecosystems by serving
as food for larger creatures. Their disruption, coupled with other
effects of greenhouse gases such as rising temperatures, could wreak
profound changes on the diversity and productivity of oceans, the
researchers said.

Escalating ocean acidity can begin to dissolve the shells faster
than the creatures can build them.

Researchers estimate the oceans have become about 30 percent more
acidic since humans began burning fossil fuels in large quantities,
exhausting carbon dioxide into the environment.

While carbon dioxide levels have been higher in the Earth's past,
and oceans more acidic, "the rate at which they're changing has
never been this fast," said Chris Sabine, another oceanographer on
the trip. Ocean life is not used to such sharp shifts.

Carbon dioxide levels in the atmosphere are now higher than they
have been at any time in at least 600,000 years. Scientists had
expected the rising levels would turn oceans more corrosive.

Northern Pacific waters where researchers detected the shift
circulate in currents along the Oregon coast.

"As predicted, the ocean is steadily becoming more acidic," said
Mark Hixon, a professor of zoology at Oregon State University and an
authority on coral reefs. "As that continues a threshold will be
crossed, and across that threshold these organisms will be unable to
make their shells, and they will die."

He said the findings are unsettling, especially coming only weeks
after findings that polar ice sheets are beginning to melt faster
than expected in a shift that could raise sea levels worldwide.

"All of this is really scary right now," said Hixon, who did not
take part in the Pacific research cruise. "It's becoming clear that
the biological effects of global warming are accelerating faster
than previously anticipated."

The research cruise, sponsored by the National Oceanic and
Atmospheric Administration and the National Science Foundation,
traversed the Pacific from Tahiti to Alaska, taking measurements
every 60 nautical miles. Scientists examined the water acidity and
chemistry, but also looked closely at pteropods, a shelled form of
plankton distantly related to land snails.

Pteropods are an important food source for salmon, herring, cod and
other fish, and their sensitivity to water chemistry makes them an
important barometer of ocean acidity.

Pteropods and other shellfish build shells from calcium carbonate,
with pteropods using an especially delicate form called aragonite.
They find enough aragonite only in water near the ocean's surface,
because deeper water becomes too acidic.

They are confined to a thin layer of surface water in the cool
northern Pacific, because cold water there holds more carbon dioxide
and is more acidic to start out.

As escalating carbon dioxide turns oceans more acidic still, that
layer of water gets thinner and thinner until pteropods get squeezed
out altogether, said Robert Byrne, a professor at the University of
South Florida who was on the research cruise.

"We're on the threshold of what is going to become a very large
effect," he said.

"People can argue back and forth whether climate is going to change,
but they can't argue that (acidity) is going to change, because we
can predict that with certainty and we can see it's happening,"
Byrne said. "The effects in the end are going to be global."

An international team of researchers reported last fall that if
fossil fuel burning continues at its current rates, oceans,
particularly in polar regions, will become too corrosive for
pteropods and other shelled ocean creatures such as sea urchins and
corals in the next century.

For more information, go to:
http://www.noaanews.noaa.gov/stories2006/s2606.htm