Mussels Lose Out As Carbon Dioxide Changes Ocean
All the carbon dioxide pouring into the atmosphere is making the oceans more acidic — and those effects appear to be striking very close to home.
Scientists have been fretting about what ocean acid will do to coral reefs and certain species of plankton. And a new study now documents a startling and rapid change in ocean acid on an island just off the coast of Washington state.
Ocean chemistry measured from Tatoosh Island found that the ocean there is becoming acidic 10 times faster than expected, according to a study published in the Proceedings of the National Academy of Sciences. And the study's author J. Timothy Wootton says the island's ecosystem is changing rapidly as a result.
During an eight-year period, he says, 10 to 20 percent of the mussels on the island have been replaced by acid-tolerant algae.
"When we project where these shifts are going in the long run, they're actually pretty alarming," Wootton says.
Given this trend, he expects 60 to 70 percent of the mussels on the island to disappear in the coming decades.
"The demise of mussels as a dominant species is potentially a pretty big deal," Wootton says. Mussels provide shelter for many animals that live along the tide line. They form a key part of the food web that includes the fish we eat.
Wootton isn't sure why the acidity changed so rapidly on this island. One lesson, though, is that ocean chemistry doesn't change uniformly over the entire planet — there are hot spots. No other studies along the Pacific coast have been monitoring acidity regularly, as this study did, so it's not clear how widespread the phenomenon is.
It's also not clear what we can do about it. Marine scientist Jane Lubchenco at Oregon State University says that even if the world abruptly shifts away from fossil fuels — and stops emitting billions of tons of carbon dioxide into the atmosphere every year — the oceans will continue to soak up carbon dioxide from the air and become more acidic.
Lubchenco says that means other ways must be found to help marine organisms survive this global threat. She recommends protecting marine life by reducing overfishing, cutting back on nutrient runoff, and creating marine reserves to protect the most valuable and vulnerable marine ecosystems.
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STEVE INSKEEP, host:
Here's one more way that human life is changing the oceans. It involves the carbon dioxide that we emit, the same substance that contributes to climate change. That carbon dioxide is also making the oceans more acidic. A new study finds the process is happening at a breathtaking rate at one study area off the coast of Washington state. Acid in the ocean is reshaping ocean life. NPR's Richard Harris reports.
RICHARD HARRIS: About half the carbon dioxide we emit into the atmosphere gets soaked up in the oceans. That's good news for us. The air isn't heating up as fast as it otherwise would. But Tim Wootton at the University of Chicago says that's bad news for the oceans.
Dr. TIM WOOTTON (Professor, Department of Ecology and Evolution, University of Chicago): As carbon dioxide increases in the atmosphere, it dissolves in the water as well. And when it does that, it reacts with water and creates carbonic acid.
HARRIS: That carbonic acid is already making ocean water slightly more corrosive around the world. But rarely has anyone really taken the time to see whether that acid is changing ocean ecosystems. Wootton just happened to include acid measurements in a long-term study he's doing on Tatoosh Island, which is half a mile off the coast of Washington state. As expected, Wootton saw a trend toward greater acidity over the past eight years.
Dr. WOOTTON: What surprised us, though, is the rate at which this was occurring. It's been occurring a lot faster, about ten times faster, than had been predicted from physical models of the ocean and the atmosphere and how they interact.
HARRIS: Wootton doesn't know why the waters at Tatoosh Island are changing so much faster than expected. Whatever the cause, it's creating rapid changes in the ecosystem as well. Wootton says 10 to 20 percent of the mussels along the coast disappeared in just that eight-year period, to be replaced by algae and other less acid-sensitive species.
Dr. WOOTTON: When we project where these shifts are going in the long run, they're actually pretty alarming. The demise of mussels as a dominant species is potentially a really big deal.
HARRIS: Wootton says soon 60 to 70 percent of the mussels on this island coastline could be gone. That's bad for more than just mussels. They are central players in the marine food web, which includes the fish we eat.
Dr. WOOTTON: So instead of a big, solid band of mussels, you'll have little patches, or mussels scattered around haphazardly. It would be like changing a system from a heavy forest into a plain that's dotted with trees.
HARRIS: Wootton's research is published in the Proceedings of the National Academy of Sciences. The looming question is whether this rapid acidification is just a fluke occurrence on one island, or whether the entire West Coast could soon feel these effects. Nobody knows because, apparently, nobody else along the coast has been monitoring the acidity of seawater this closely. But Jane Lubchenco at Oregon State University is worried.
Dr. JANE LUBCHENCO (Professor of Marine Biology and Zoology, Oregon State University): Ocean acidification is likely one of the most serious and insidious changes under way. And it was one that was not even on our radar screen. And it looms large.
HARRIS: Lubchenco says biologists are focused mostly on the risk to corrals and plankton that have calcium shells that can literally dissolve away if the ocean gets too acidic. But the latest study shows the problems are likely also much closer to home. And it's likely to get worse for a long time to come. Lubchenco says it won't be easy to curtail our emissions of carbon dioxide.
Dr. LUBCHENCO: Even if we do, it's not going to fix the ocean acidification problem immediately. There's a long time lag in the system.
HARRIS: The oceans will keep soaking up the carbon dioxide that's already in the atmosphere. So, she says, at least we should take whatever other steps we can to reduce the stresses on marine life. Richard Harris, NPR News.
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INSKEEP: You can read more about the ocean's role in the carbon cycle by going to npr.org. This is NPR News. Transcript provided by NPR, Copyright National Public Radio.
