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DATE: December 16, 2019

SNIP: The waters off California are acidifying twice as rapidly as elsewhere on Earth, according to a study published Monday, which suggests that climate change is likely hastening and worsening chemical changes in the ocean that could threaten seafood and fisheries.

Oceans play an important role in the planet’s delicate carbon cycle, acting as a crucial reservoir that absorbs and stores carbon dioxide from the atmosphere. But the new research finds that although oceans can withstand some natural variations in climate, global warming may be adding to the stress on those ecosystems and overwhelming their ability to cope.

“The system is adapted to experience and be able to thrive in a variable environment, but when you add extra stress, these changes become more extreme,” said Emily Osborne, a researcher at the National Oceanic and Atmospheric Administration, or NOAA, the lead author of the study, which was published in the journal Nature Geoscience.

Osborne and her colleagues analyzed almost 2,000 fossil shells of a tiny organism known as planktonic foraminifera to create a 100-year history of ocean acidification along the California coast. The organisms, which live for only about a month, use calcium carbonate to build their shells, which means they leave behind clues about their environment.

As oceans become more acidic, sea creatures struggle to build up hardier shells, Osborne said, which allowed her and her colleagues to study the thickness of foraminifera shells and trace levels of ocean acidity back through time. They found that the organisms’ shells were thinning as oceans became more acidic.

“We saw a clear, long-term declining trend with shell thickness that aligns with the signature of carbon that comes from the atmosphere,” she said.

Previous studies have shown that oceans have experienced a decline of 0.1 in pH since the Industrial Revolution in 1750. The pH scale ranges from 0 to 14, and lower values are more acidic, while higher values are more basic.

Similar data for California’s coastal waters for that entire period don’t exist, but Osborne and her colleagues found that in just the past century, California’s coastal waters have experienced a 0.21 decline in pH — twice the global average over more than 2½ centuries.

Although more research is needed, Osborne said, the chemical changes could have negative consequences for the vibrant fisheries off California and elsewhere around the world.