Modern mussel shells much thinner than 50 years ago

http://www.eurekalert.org/pub_releases/2016-06/uocm-mms061416.php

Public Release: 14-Jun-2016
Modern mussel shells much thinner than 50 years ago
Shells from the Pacific Northwest are nearly a third thinner now than specimens collected in the 1970s
University of Chicago Medical Center

Shells of California mussels collected from the Pacific Ocean off the coast of Washington in the 1970s are on average 32 percent thicker than modern specimens, according to a new study published by University of Chicago biologists.

Shells collected by Native Americans 1,000 to 1,300 years ago were also 27 percent thicker than modern shells, on average. The decreasing thickness over time, in particular the last few decades, is likely due to ocean acidification as a result of increased carbon in the atmosphere.

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As humans burn fossils fuels, the oceans absorb a large portion of the additional carbon released into the atmosphere. This in turn causes pH levels of ocean water to drop, making it more acidic. Mussels, oysters, and certain species of algae have difficulty producing their calcium carbonate shells and skeletons in such an environment, and can provide an early indicator of how increasing ocean acidification affects marine life.

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The researchers also point out that their findings raise concerns about the California mussel's ability to retain its role as a foundational species in these waters. Decreased shell thickness makes them increasingly vulnerable to predators and environmental disturbances. This in turn could affect interactions with hundreds of other species of organisms that live near mussel beds in tidal waters.

"The California mussel is a common species along the entire west coast of the United States, and their fate will be linked to that of a rich diversity of predators, including sea stars and sea otters, as well as myriad species that are part of the mussel bed habitat," Pfister said. "It is imperative that we understand more about how these species will change as ocean conditions change."