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http://www.google.com/hostednews/afp/article/ALeqM5i_Z1zrB_r470q
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WASHINGTON � High levels of pollution may be turning the 
planet's oceans acidic at a faster rate than at any time in the 
past 300 million years, with unknown consequences for future sea 
life, researchers said Thursday.

The acidification may be worse than during four major mass 
extinctions in history when natural pulses of carbon from 
asteroid impacts and volcanic eruptions caused global 
temperatures to soar, said the study in the journal Science.

An international team of researchers from the United States, 
Britain, Spain, Germany and the Netherlands examined hundreds of 
paleoceanographic studies, including fossils wedged in seafloor 
sediment from millions of years ago.

They found only one time in history that came close to what 
scientists are seeing today in terms of ocean life die-off -- a 
mysterious period known as the Paleocene-Eocene Thermal Maximum 
about 56 million years ago.

Though the reason for the carbon upsurge back then remains a 
source of debate, scientists believe that the doubling of 
harmful emissions drove up global temperatures by about six 
degrees Celsius and caused big losses of ocean life.

Oceans are particularly vulnerable because they soak up excess 
carbon dioxide from the air which turns the waters more acidic, 
a state that can kill corals, mollusks and other forms of reef 
and shell organisms.

"We know that life during past ocean acidification events was 
not wiped out -- new species evolved to replace those that died 
off," said lead author Barbel Honisch, a paleoceanographer at 
Columbia University's Lamont-Doherty Earth Observatory.

"But if industrial carbon emissions continue at the current 
pace, we may lose organisms we care about -- coral reefs, 
oysters, salmon."

Honish and colleagues said the current rate of ocean 
acidification is at least 10 times faster than it was 56 million 
years ago.

"The geological record suggests that the current acidification 
is potentially unparalleled in at least the last 300 million 
years of Earth history, and raises the possibility that we are 
entering an unknown territory of marine ecosystem change," said 
co-author Andy Ridgwell of Bristol University.

The UN Environment Program released a report in 2010 that warned 
carbon emissions from fossil fuels may bear a greater risk for 
the marine environment than previously thought.

Rising acidity levels have an impact on calcium-based lifeforms, 
ranging from tiny organisms called ptetropods that are the 
primary food source, to crabs, fish, lobsters and coral, it said.

The UN report called for cuts in human-made CO2 emissions to 
reduce acidification and support for further work to quantify 
the risk and identify species that could be most in peril.