The problem of increasing acidity developing in the world's oceans has reared its head on the U.S. West Coast, where scientist have confirmed the acidity is dissolving shells of miniscule marine snails forming an important link of the marine food chain.

The small free-swimming creatures known as pteropods, represent a significant food source consumed by mackerel, salmon and herring, research team led by the National Oceanographic and Atmospheric Administration says.

The problem of dissolving shells has almost doubled in habitats near shoreline since pre-industrial times, and human-caused ocean acidification could make coastal waters more corrosive by 70 percent by 2050.

"Our findings are the first evidence that a large fraction of the West Coast pteropod population is being affected by ocean acidification," says lead study author Nina Bednarsek of NOAA's Seattle-based Pacific Marine Environmental Laboratory.

Acidification, a result of the oceans absorption of much of the carbon dioxide greenhouse gas emitted into the atmosphere from human activities is changing ocean chemistry. A portion of the CO2 forms corrosive carbonic acid.

Species with shells of calcium carbonate such as oysters, mussels and corals, along with pteropods and other vital food-chain species are particularly prone to the damaging effects of those chemistry changes.

In their study, the researchers traced movements of acidic waters during the season from April until September, a period of upwelling when winds move the corrosive CO2-laden water from hundreds of feet deep into the shallower continental shelf waters.

The arrival of increasingly acidic waters is what drives the harm to the pteropods; as their shells are dissolved they become more vulnerable to diseases, suffer reduced reproductive rates and are less able to escape predators.

The problem could have a wider scope than previously thought, the researchers said.

"Dissolving coastal pteropod shells point to the need to study how acidification may be affecting the larger marine ecosystem," Bednarek says. "These nearshore waters provide essential habitat to a great diversity of marine species, including many economically important fish that support coastal economies and provide us with food."

The study had been reported in the Proceedings of the Royal Society B.

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