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October 2011 Issue

In a World of Acidifying Oceans, Life Hangs on a Precipice
By Alanna Mitchell
I've spent a decade piecing together the puzzling implications of the growing proportion of carbon dioxide gas in the atmosphere. That means reading academic papers published in journals, interviewing scientists on each of the seven continents as they conduct their studies and bearing witness myself to the effects that they have been laboring to explain to us. And then translating all that in articles, books and public talks in a bid to tell readers what scientists are finding.

At first I thought the changes to the seasons—the patterns of climate that tell us when we can sow and reap and whether we'll have enough rain to grow food—were the most important consequences of this high-carbon world we are creating. And, to be sure, these changes are enormous. It was only when I started finding out about the impact of a high-carbon ocean that I realized the consequences may be even worse.

As we burn the fossilized bodies of plants and animals that lived millions of years ago—we call them coal, oil and gas—we are releasing the ancient carbon from their bodies into atmosphere in the form of carbon dioxide gas. Some of that is reabsorbed into plants and soil but about a third stays in the air. Before the industrial revolution began a couple of centuries ago, there were about 280 parts of carbon dioxide per million in the atmosphere. Today, the figure is 393 parts per million, a jump of 40 percent in a very short time, speaking in geologic timescales. It would be far higher except that, like the land, the ocean has absorbed about a third of that carbon.

There's a big difference between carbon in the air and in the ocean. Carbon dioxide in the atmosphere hangs there, holding heat against the body of the Earth and making the seasons forgetful. But it's also chemically inert. In the ocean, it is not. Carbon dioxide reacts chemically with water to make carbonic acid, acidifying the ocean. Today, a growing number of ocean-monitoring technologies are showing the ocean is 30 percent more acidic than it was before the industrial revolution. That's more acidic than it has been for about 55 million years.

Why does it matter? For one thing, pH is a key determinant of life. When it changes, the ocean's ability to support life changes. It's the same in humans. Blood pH is one of the first things doctors measure when a baby is born to see how healthy the child is. It's a sensitive measure and whole levels of protection are set up in the ecosystem of your body to make sure it can't change very much, because if it changes even very slightly, you die.

It's similar in the larger ecosystems of the planet. When ocean pH changes, especially if it's a major change over a short period of time, it's grim news for the creatures that live in the ocean. Some are already having trouble maintaining their own internal chemistry. Embryos—of fish and other creatures—are particularly vulnerable. As we put ever more ancient carbon into the air and it gets absorbed into the ocean, the ocean will become even more acidic.

The second reason pH is so important is that as the ocean becomes more acidic, the calcium it contains becomes less available to the marine creatures that need it to build shells, teeth, bones and coral reefs. Scientists are already tracking sea snails in the Southern Ocean around Antarctica that have thin, pitted shells and oysters in Puget Sound that are failing to thrive. Researchers are worried about the fate of mussels in California, too.

And coral reefs, three-quarters of which are already in danger around the world from overfishing, land runoff and high water temperatures, could be gone in as little as 20 years as the acidifying water breaks down their ability to build their bony structures.

The bottom line is that life in the ocean is in trouble and that trouble grows with every molecule of carbon dioxide that goes into the atmosphere. That matters because ocean life controls all life on Earth, strange as it seems to us land-dwellers. In other words, if all life on land were to die off tomorrow, life in the ocean would be fine. Better without all that pressure from humans. But if life in the ocean were to die off, life on land would also perish. Marine plankton, many of which use calcium to make their shells, produce every second breath of oxygen we breathe. The ocean also regulates the planet's carbon and nitrogen cycles.

In fact, the planet's five mass extinctions—the last was 65 million years ago when the dinosaurs vanished—were likely sparked by the same changes to ocean chemistry that we're seeing today. The ocean is the switch of life. Our human hands are on the switch.

What to do? Ocean acidification is irreversible except over long spans of time. But if we stopped putting all that ancient carbon into the atmosphere, and therefore into the ocean, we could slow down the pace of acidification and that would help marine life adjust to the chemical changes.

Scientists are key to the process. Not only are they the diagnosticians of the disease, but they're also the ones who will keep gathering the data we need to see how quickly things are progressing—or reversing. And many of them will be the ones to come up with solutions. Already, engineers are figuring out how to build offshore wind, solar and tidal farms, some of the carbon-free alternatives we'll need. And in the meantime, many people in the oil and gas industry are finding smart new ways to extract fossil fuels more efficiently.

As citizens, we can insist that the high-carbon ocean be taken seriously at international carbon talks, and that these dreadful marine consequences put an even greater urgency behind the need to shift away from fossil fuels and toward the new forms of energy. Life as we know it is at stake.
Alanna Mitchell is a Canadian journalist. Last year she won the Grantham Prize for Excellence in Reporting on the Environment for her international best-seller, "Seasick: Ocean Change and the Extinction of Life on Earth." It was the first time a Canadian won the award, and the first time the award was awarded for a book rather than a series of articles.


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Sea Technology is read worldwide in more than 110 countries by management, engineers, scientists and technical personnel working in industry, government and educational research institutions. Readers are involved with oceanographic research, fisheries management, offshore oil and gas exploration and production, undersea defense including antisubmarine warfare, ocean mining and commercial diving.