Increased acidity in our oceans as a result of burning fossil fuels is the cause of a thinning of the California mussel shell, according to a new study by UChicago biologists.
California mussel shells collected off the coast of Washington state in the 1970s are, on average, 32% thicker than modern specimens, according to the report published in the Proceedings of the Royal Society B.
This trend is seen throughout millennia with shells collected by Native Americans 1,000 to 1,300 years ago an average of 27% thicker than modern shells.
“Archival material provided by past researchers, the Makah Tribal Nation, and the Olympic National Park allowed us to document this intriguing and concerning pattern in shell thickness,” said Cathy Pfister, professor of ecology and evolution and lead author.
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.
The researchers compared the thicknesses of modern mussel shells with those collected by the Makah tribe of Tatoosh Island off the coast of Washington between 668 and 1008AD and shells from the 1970s. On average, the shells provided by the Makah Cultural and Research Centre were 27.6% thicker than modern counterparts. Shells from the 1970s were 32.2% thicker. Shells collected from a different Native American site in Sand Point, Washington, dating between 2150 and 2420 years old were almost 94% thicker than modern shells.
The researchers point out that their findings raise concerns about the California mussel’s ability to retain its role as a foundational species. 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 study can be found on the UChicago website.
