Saturday, September 22, 2007

Ocean acidity from CO2 could violate EPA water standards by 2050

The acidification of the oceans is proceeding so fast that
the seas could violate Environmental Protection Agency
guidelines by the middle of the century.
That's the assessment of a multinational team of scientists
writing in the Sept. 25 issue of Geophysical Research
But EPA water quality criteria are hardly the problem.
They're just paper and ink. The problem for us, said a
Hawai'i researcher who co-wrote the report, is what that
acidification could do to life around the Islands.
One key issue: the slowing growth of coral reefs that
protect many of our shorelines.
Richard E. Zeebe, an assistant professor in oceanography
with the University of Hawai'i's School of Ocean and Earth
Science and Technology, said the higher acidity could
decrease the rate of production of forms of calcium
carbonate like calcite and aragonite. (Calcium carbonate
is a base, and is eaten up by acidity.)

These compounds are the building blocks of coral reefs,
seashells and other forms of life—and they form much of
the sand on the beaches and the sea floor.

“Coral skeletons are made of aragonite, so it's likely
that calcification rates in corals will slow down with
potentially detrimental consequences for coral reef
ecosystem structure,” he wrote in an email.

How soon could there be issues?
“Given the response we see in experimental studies with
coral, it's likely that impacts are noticeable within a
few decades. Some coral studies indicate that
calcification rates could be reduced by about 50 percent
in 2050 relative to preindustrial values,” he wrote.

The paper in which Zeebe was a co-author argues that
“changes in ocean chemistry within the ranges predicted
for the next decades and centuries present significant
risks to marine biota.”

The increasing acidity is caused by the increasing amount
of carbon dioxide (CO2) in the atmosphere. One of the
other big results of this is global warming.

Before the Industrial Revolution, there were 280 parts
per million of carbon dioxide in the atmosphere. As
fossil fuels like oil and coal began forming the basis
of the world's energy supply, CO2 was a significant waste
product and ended up in the atmosphere.

Today, there's about 380 parts per million CO2 in the air.
And the researchers figure that at current rates of
fossil fuel burning, it could be 500 parts per million
by 2050 and 760 parts per million by 2100.

Lead author Ken Caldeira of the Carnegie Institution
Department of Global Ecology,

said that about a third of the CO2 formed by fossil
fuel burning ends up dissolved in the oceans. He
explains the chemistry.

“When CO2 gas dissolves in the ocean it makes carbonic
acid, which can damage coral reefs and also hurt other
calcifying organisms, such as phytoplankton and
zooplankton, some of the most critical players at the
bottom of the world's food chain.

“In sufficient concentration, the acidity can corrode
shellfish shells, disrupt coral formation and interfere
with the oxygen supply,” he wrote.

Caldeira said that for the health of the planet,
atmospheric CO2 must not be allowed to exceed 500 parts
per million.

“We need to start thinking about carbon dioxide as an
ocean pollutant. That is, when we release carbon dioxide
into the atmosphere, we are dumping industrial waste in
the ocean.”

The researchers said the solution is conservation and
quickly changing to a global energy system that produces
very little carbon dioxide.

© 2007 Jan W. TenBruggencate

No comments: