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  The Sydney Morning Herald 12 Sep 07
Ocean time bomb
 Acid caused by greenhouse gases is ravaging marine life.
Graham Phillips examines this devastating threat to our seas.

Much of the carbon dioxide that is belched into the skies by cars and industry ultimately ends up in our oceans.

There it dissolves in a process called ocean acidification.

Science has become aware of it only over the past few years, but the consequences of this hidden side effect of our greenhouse gas emissions could be devastating. Perhaps even bigger than climate change.

The acidification of our seas threatens to ravage marine life around the globe and ultimately even damage land dwellers, including us.

A disturbing aspect of this phenomenon is that it has been going on under our noses for decades and we haven't been aware of it. And even worse, much of the carbon we've put into the atmosphere during those years of ignorance is poised to further acidify our oceans over coming decades.

And, unfortunately, there is little we can do about it.

"This problem will continue to affect the oceans even if we stopped all carbon emissions now, and will continue for probably centuries," says Dr Will Howard, a marine geologist at the Antarctic Climate and Ecosystems Cooperative Research Centre in Hobart.

Howard and his team have just uncovered the first evidence that ocean acidification is starting to affect sea life.

They've discovered that some of the plankton in the Southern Ocean is already finding it more difficult to make shells because the water there is becoming too acidic.

These microscopic marine organisms may be less glamorous than the whales and seals but plankton plays a vital role in the ocean web of life. It is at the very bottom of the food chain, and when it suffers, so does the life above it.

"Many of the fish and other plankton in the ocean that feed on these organisms will all be affected," says Howard. Krill, for example, eat plankton, and whales and seals eat krill. "This will have an ecological cascade effect right up to parts of the food web that are important to human beings, that is fish, shellfish, for example.

"The detail of how the ocean's ecosystems will be altered is impossible to forecast at this early stage, but it is likely we will eventually see the consequences on our dinner plates.

"We will have to adapt perhaps our whole seafood industry to live with a very different ocean to what we have today," says Howard.

The phenomenon is the result of simple chemistry. Carbon dioxide dissolves in seawater to form weak, carbonic acid. The problem is, acids dissolve limestone, or calcium carbonate, which is the main constituent of seashells.

As the oceans become more acidic, it will become increasingly difficult for creatures' shells to form.
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