The study finds that corrosive water off the U.S. West Coast is dissolving the shells of a marine snail, also known as a sea butterfly, that is a key player in the coastal food chain.

Researchers worry that the mollusks' weakened shells could have far-reaching consequences for the animals that eat them, such as fish and marine mammals.

Salmon, herring, and other commercially important species rely on a snail-rich diet. But with many sea butterflies now growing thin, pitted, bumpy shells—a clear sign of ocean acidification—their ability to reproduce, protect against infection, and even swim is being compromised.

"We've been talking about ocean acidification as a problem for the future," says Scott Doney, an oceanographer with the Woods Hole Oceanographic Institution