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Oceans becoming acid soup


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Silently and steadily, a tragedy is unfolding beneath the ocean's waves: Coral reefs around the world are disappearing. According to some projections, there could be few, if any, left by the end of the century.

This dire and credible prediction has shocked many marine scientists, who had not realized how close to the tipping point coral reefs are. The news is especially disheartening because 2008 is the International Year of the Reef.

The culprit here is carbon dioxide, the greenhouse gas that is responsible for global warming and that also is turning our oceans into an acid bath.

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Here's the problem. When carbon dioxide enters the ocean, it reacts with water to form carbonic acid. A few other chemical steps ensue, with the outcome that fewer carbonate ions are available for biological systems. Corals are not the only organisms that suffer. All shell-forming marine creatures are adversely affected.

Taking a human analogy, it would be as if your bones could no longer keep growing.

We are seeing the effects of ocean acidification. Today, the concentration of carbon dioxide in Earth's atmosphere is more than 380 parts per million. That's more than at any time during the past 20 million years.

About 25 percent of this carbon dioxide ends up being absorbed by the oceans. As carbon dioxide levels have risen during the industrial era, the average pH level in the ocean, an indicator of acidity, has dropped by 0.1 pH unit. (On the pH scale, a lower number means more acidic.)

That might not sound like much, but evidence from Antarctic ice cores shows that the global average is lower than at any time over almost half a million years. As the Science article notes, changes in atmospheric carbon dioxide over the last century "are 2 or 3 orders of magnitude higher than most of the changes seen in the past 420,000 years."
JanforGore

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