Climate scientists have long feared that as atmospheric CO2 increased the oceans would become increasingly acidic. While large quantities of carbon dioxide are disbursed into the atmosphere, the oceans also absorb larger and larger amounts of the gas. This causes increased acidity in the water and the corrosive effect can endanger marine ecosystems.

Recent tests by the National Oceanic and Atmospheric Administration (NOAA) off of the U.S. west coast have confirmed that this is happening and that it is occurring at a faster pace than predicted. Researchers gathered free swimming snails, also known as pteropods, during west coast survey cruises in 2011 and 2013.

They found that many of the animals, which are a food staple for many commercial fish including salmon and herring, had severely corroded shells. Shellfish with calcium carbonate skeletons or shells including snails, corals, oysters and mussels are expected to be one of the first indicators of acidification.

“Our findings are the first evidence that a large fraction of the West Coast pteropod population is being affected by ocean acidification. Dissolving coastal pteropod shells point to the need to study how acidification may be affecting the larger marine ecosystem. 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,” said Nina Bednarsek, Ph.D., of NOAA’s Pacific Marine Environmental Laboratory in Seattle in a statement.

The scientists estimate that the number of pteropods with dissolving shells has doubled since the pre-industrial era and is on track to triple by 2050. In the region from northern Washington to central California a full 53 percent of the snails showed shell deterioration.

“We did not expect to see pteropods being affected to this extent in our coastal region for several decades. This study will help us as we compare these results with future observations to analyze how the chemical and physical processes of ocean acidification are affecting marine organisms,” said William Peterson, Ph.D., an oceanographer at NOAA’s Northwest Fisheries Science Center.

The highest levels of acidification occur from April to September during what is called the “upswelling season.” During this period winds bring water from depths of 400 to 600 feet onto the continental shelf. In addition to snails and shellfish, it is believed that increased acidification could cause harm to young fish and animals in a larval stage. This, in turn, could disturb the overall food chain and ecosystem of the world’s oceans.

“Acidification of our oceans may impact marine ecosystems in a way that threatens the sustainability of the marine resources we depend on. Research on the progression and impacts of ocean acidification is vital to understanding the consequences of our burning of fossil fuels,” said Libby Jewett, Director of the NOAA Ocean Acidification Program.

The complete findings of the NOAA team can be found in the journal Proceedings of the Royal Society B. Additional information is also available at NOAA.gov.