Under the Sea — March 5, 2015 at 5:00 am

The Puzzle of Acid and the Sea

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©istockphoto/mauriziobiso

©istockphoto/mauriziobiso

If you happen to be an oyster or a clam, these are not good times. Stories about warmer, snowless winters and summer droughts get the press, but something else is also affecting the sea—and it’s all related. The ocean is becoming ever so slightly more acidic. If you’re a beachgoer, you might notice at first. But it’s happening, and here’s what we can do about it.

What Is It?
Ocean acidification is part of the legacy of fossil fuels and climate change. When we burn fossil fuels, a certain amount of carbon dioxide ends up in the ocean. Carbon dioxide and saltwater combine to form carbonic acid.

Shelling Out More For Shellfish
The major impact of carbonic acid is weakening the shells of creatures with hard exoskeletons. The main effect has been on shellfish like oysters and clams, especially during the vulnerable early growth stage. Oyster growers in Washington and Oregon have reported slower growth, weaker production, and more fragile shells. In some places, like Puget Sound, the problem is compounded by of pollution from population centers and farm chemicals. As populations decline, you may find yourself paying more for oysters, clams, scallops, and mussels.

Selling the Shelling
What to do about ocean acidification? One tactic involves using the mountains of shells piled up outside oyster harvesters and seafood restaurants. Most of the time, they’re either hauled to the dump or sold as fertilizer. Depositing shell material in shallow bays adds calcium carbonate to the water where shellfish grow. Calcium carbonate is alkaline, so as the shell material degrades and enters the water column, it may make the water less acidic. It’s an unproven tactic, but it has promise.

Kelp, I Need Somebody!
Another way to combat the rising acid content is with healthy seaweed beds. Plants like kelp, other seaweeds, and eelgrass absorb carbon dioxide just like trees do. Taking up this carbon dioxide will reduce the amount that can turn into carbonic as well as create a healthy environment for marine life in general. Kelp, which grows particularly quickly and therefore collects a lot of carbon dioxide; this may be one reason why acidification is less severe in places like California’s Monterey Canyon, where healthy kelp forests are maintained by urchin-eating sea otters, than in otterless Oregon and Puget Sound.

Tales of the Tailpipe
But at its root, ocean acidification is a result of climate change. Spreading shells and growing kelp may treat the symptoms, but treating the cause starts with us. It mans driving more efficient cars and appliances, insulating our homes and offices, and supporting renewable power.

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