Carbon Dioxide Emissions May Harm Ocean Life

From: Donald L Ferrt (wolfbat359_at_mindspring.com)
Date: 07/18/04 

Date: 18 Jul 2004 05:13:38 -0700

http://www.reuters.co.uk/newsArticle.jhtml?type=scienceNews&storyID=5685015&section=news

Carbon Dioxide Emissions May Harm Ocean Life
Thu 15 July, 2004 22:33
 
By Christopher Doering

WASHINGTON (Reuters) - The world's oceans have absorbed nearly half of
the carbon dioxide emitted by humans during the last 200 years,
creating potential long-term challenges for corals and free-swimming
algae, according to two studies released on Thursday.

An international team of scientists found that oceans have taken in
about 118 billion metric tons of carbon dioxide from human activities
between 1800 and 1994, accounting for nearly a third of their
long-term carrying capacity.

These findings could pose a long-term risk for marine organisms, such
as corals, which have greater difficulty in forming their outer shells
as carbon dioxide levels increase, researchers found.

"There is a price to pay in this process, and that is with living
organisms," said Richard Feely, a marine chemist with the National
Oceanic and Atmospheric Administration, the lead author on one of the
studies.

The research was published in the July issue of "Science."

Oceans, which cover about 75 percent of the Earth's surface, have seen
the amount of carbon dioxide they absorb fall to 30 percent as trees
and plants soak up more of the gas before it reaches the water.
Currently, 20 percent is taken in by foliage, with the remaining 50
percent staying in the atmosphere.

The 15-year study, conducted and analyzed with the help of several
researchers around the world, looked at nearly 72,000 samples taken in
the Atlantic, Pacific and Indian oceans.

Analysis of carbon dioxide since the industrial age has shown that
concentration levels in the atmosphere have increased to about 380
parts per million (ppm) from 280 ppm two centuries ago. Without ocean
absorption, carbon dioxide levels in the atmosphere would be about 55
ppm higher.

The data found that even though the oceans continue to absorb more
carbon dioxide, they are far from being saturated. Currents stir the
ocean very slowly by pulling deep ocean water to the surface, where it
is able to absorb more carbon dioxide.

"The oceans have a capacity to continue to take in CO2 for thousands
of years with the slow mixing time," said Christopher Sabine, NOAA
oceanographer and lead author of the other study.

The greatest threat to increasing levels of carbon dioxide is to
species that live in the upper 10 percent of the ocean.

As ocean surfaces capture and store carbon, the slow circulation of
water keeps the gas more highly concentrated where these creatures
live.

The change in ocean chemistry reduces the level of carbonate ions
needed by corals and other organisms to generate their shells. In
areas where the ion level has fallen too low, calcium carbonate shells
can begin to dissolve.

Researchers said that while the long-term impact on these creatures
and other species that depend on them for food is uncertain, they will
closely monitor how carbon dioxide absorption is affecting the food
chain.

"We might see the structure of the food web change ... and see shifts
in species competition" in the ocean ecosystem, said Victoria Fabry, a
biologist at California State University who worked on the research.

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