Increasing acidity dissolving ocean snails

The Pacific Ocean’s increasing acidity is dissolving the shells of tiny sea snails that are a vital food source for fish such as salmon and sole, according to new research by the National Oceanic and Atmospheric Administration.

The ocean’s changing chemistry is the result of carbon dioxide emissions from industry and agriculture. Increasing acidity means a reduction in carbonate ions, which the snails — known as pteropods — need to grow their shells.

“This is the first time we’ve been able to tease out the percentage of human-caused carbon dioxide from natural carbon dioxide along a large portion of the West Coast and link it directly to pteropod shell dissolution,” Richard Feely, a NOAA senior scientist, said in a statement.

Ocean acidification has been dubbed the “evil twin” of global warming because the same carbon dioxide emissions that cause climate change also dissolve into seawater, threatening the world’s oceans.

“Our research shows that humans are increasing the acidification of U.S. West Coast coastal waters, making it more difficult for marine species to build strong shells,” said Feely, who led the research, published in the latest issue of the journal Estuarine, Coastal and Shelf Science.

The researchers created a detailed map of the varying carbon dioxide concentrations in different sections of the Pacific Ocean off America’s West Coast. They used several decades of measurements taken through the U.S. Global Ocean Carbon and Repeat Hydrography Program, as well as new data from four NOAA West Coast research cruises conducted from 2007 to 2013

They found that concentrations of human-caused carbon dioxide are greatest in shallow coastal waters but diminish where water is deeper.

Then they analyzed the pteropod shells in those different areas. They found that more than half of pteropod shells collected from coastal waters with the highest carbon dioxide concentrations were severely dissolved. In deeper offshore waters, a smaller portion of pteropods shells — between 10 to 35 percent — showed damage.

The shell dissolution affects the swimming ability of the snail, the size of the head of a pin, according to earlier research by Nina Bednaršek of the University of Washington. This may hamper its ability to protect itself from predators.

“We estimate that since pre-industrial times, pteropod shell dissolution has increased 20 to 25 percent on average in waters along the U.S. West Coast,” Bednaršek said in a statement.

Like a sponge, our oceans are absorbing increasing amounts of carbon dioxide from the atmosphere, NOAA said. It estimates that the world’s seas have absorbed more than 150 billion metric tons of carbon from human activities over the past 200 years. That’s a worldwide average of 15 pounds per person a week, enough to fill a coal train long enough to encircle the equator 13 times every year.

The team wants to learn how ocean acidification affects the larger marine ecosystem. If damaged, it could threaten human food supply, livelihoods and economies.

“This new research suggests we need a better understanding of how changes in pteropods may be affecting other species in the food chain,” said Bednaršek, “especially commercially valuable species such as salmon, sablefish and rock sole that feed on pteropods.”

Lisa M. Krieger, Bay Area News Group, via Santa Cruz Sentinel, 23 November 2016. Article.

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