February 26, 2010

Lobsters show unusual reaction to excess carbon dioxide: Faster shell growth

— Lobster is king in Maine when it comes to seafood and the coastal economy.

A study published this week in the journal Geology seems to say the Maine icon may soon be king of the ocean as well.

Researchers at the University of North Carolina and the Woods Hole Oceanographic Institution in Massachusetts found that a few sea creatures, including lobsters, appeared to grow shells faster as the water in their laboratory tanks absorbed carbon dioxide and became more acidic.

The study was intended to simulate the direct effects of what scientists say is happening to the world's oceans as they absorb carbon dioxide from fossil fuel combustion, the same emissions that are linked to global warming.

One article about the research ran on the Web site Futurity, under a headline that would surely excite Maine lobster fishermen and frighten small children: ''Jumbo shellfish rule in acidic oceans.''

While corals, clams, snails, oysters, scallops and other organisms showed signs of dissolving in the acidic water, lobsters, shrimp and crabs built shells quicker. The reasons aren't entirely understood, but lobsters may somehow convert the dissolved carbon from the atmosphere into a form they can use to build new shells, the researchers wrote.

Does that mean we'll have to start building bigger lobster traps?

Don't start melting the butter yet. Scientists say it's a little more complicated than that.

''It's very complex at the organism level,'' said Mark Green, a marine science professor at Saint Joseph's College in Standish and a leading researcher on ocean acidification and clams. ''The study just shows there's a lot we don't know about what's going on.''

Ocean acidification is emerging as an urgent concern for scientists. Green and other marine scientists here say its effects could be more damaging, and happen more quickly, than those tied to global warming.

The world's oceans have become 30 percent more acidic over the past two decades, and the trend is expected to continue because of the amount of carbon dioxide in the atmosphere today, researchers say.

Green, who grows oysters in Casco Bay when he's not teaching or doing research, will go to Washington, D.C., next week with fishermen and shellfish growers from around the country to urge members of Congress to cut carbon emissions and slow the rate of acidification.

The laboratory findings published this week confirmed Green's research, which showed that rising acidity in Casco Bay is killing clams and making it difficult for others to make and maintain their shells.

That doesn't necessarily prove that clams are doomed, Green said.

''There are going to be plenty of species that are significantly impacted by (acidification), but there is so much to understand about the ability of organisms to adapt,'' he said.

He's also far from convinced that lobsters will thrive in the increasingly acidic sea.

For one thing, no one knows how lobsters will adapt to all the other changes in the ocean that will come from acidification, Green said.

''When you're simultaneously removing other parts of the ecosystem that lobsters may rely upon as a food item, what's the net effect going to be?'' he said.

There also are questions about the long-term effects on lobsters' growth, health and reproduction.

The study also looked narrowly at shell mass and didn't consider what was happening to rest of the animal.

Robert Steneck, a marine biologist at the University of Maine and one of the state's top lobster scientists, called the new study intriguing.

He remains concerned about the lobster's future.

''Can a (calcium-dependent) organism live and calcify for years in acidic seas? I'm a skeptic on that point,'' he said in an e-mail.

 ''Nevertheless, we clearly see that not all organisms respond to acidification in the same way.''

As with climate change, there is no doubt there will be winners and losers in nature as oceans acidify, scientists say. And the odds for lobsters may have improved this week.

The ocean is a complicated place, however, and it's basically in the midst of a giant chemistry experiment, Green said. ''It's nearly impossible to tease out what's going to happen at the organism level.''

Staff Writer John Richardson can be contacted at 791-6324 or at:

jrichardson@pressherald.com

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