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Ocean Acidification Affecting California Mussels

Buoys in the water at the Carlsbad Aquafarm where owners grow oysters and mussels on Aug. 26, 2019.
Erik Anderson
Buoys in the water at the Carlsbad Aquafarm where owners grow oysters and mussels on Aug. 26, 2019.

A UC San Diego researcher says an increasingly acidic ocean is having an impact on shellfish that live in the nearshore environment.

Graduate student Elizabeth Bullard studied recent mussel samples and compared them to records of mussels captured along the California coast 60 years ago.

Ocean Acidification Affecting California Mussels
Listen to this story by Erik Anderson.

Bullard expected to find that the animal’s shells were harder and contained more of the carbonate mineral aragonite as the shellfish adjusted to a warming ocean.


Instead, she found mussel shells contained more calcite — a much softer material that makes the animal more vulnerable to predators or strong waves near shore.

RELATED: San Diego’s Climate Crisis: Oyster Hatchery Challenged By Warming Ocean

Bullard’s research found the modern-day mussels were adapting to the more acidic water.

“Are the shells really weakening that much? Or do they have alternative ways to compensate for the change in mineralogy?” Bullard asked.

Bullard said the shellfish is considered a foundation species because it has such a marked impact on its habitat.


Bullard studies the animal because mussels play an important role in nearshore habitats and she worries those areas could be permanently changed if the mussel’s numbers dwindle.

RELATED: San Diego Coastal Marshes May Become Important Tools To Battle Climate Change

“Even if some species do benefit,” Bullard said. “In terms of their physiology or their metabolism with ocean acidification, because every organism is so intricately tied together in the ocean, if one species doesn’t do well all other species are going to be impacted.”

The shift in the last 60 years is pretty dramatic, according to Bullard.

Her findings were published in the Proceedings of the National Academy of Sciences.