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100 years of tiny seashells reveal alarming trend threatening West Coast seafood

The Sacramento Bee

December 16, 2019

Roughly 100 years worth of tiny shells resting on the Southern California seafloor have revealed an alarming trend that could spell trouble for the West Coast seafood industry, a new study says.

The research, published Monday in the journal Nature Geoscience, suggests that the Pacific Ocean along California is acidifying twice as fast as the global average, scientists from the National Oceanic and Atmospheric Administration said in a news release on the findings.

Acidification is a serious threat for the seafood industry, researchers said, explaining that “California coastal waters contain some of our nation’s more economically valuable fisheries, including salmon, crabs and shellfish. Yet, these fisheries are also some of the most vulnerable to the potential harmful effects of ocean acidification on marine life.”

Researchers said the findings looked at “the progression of ocean acidification in the California Current Ecosystem through the twentieth century.” That ecosystem extends from southern British Columbia in Canada to Baja California in Mexico, encompassing the Washington and Oregon coasts, according to NOAA.

Higher acidity levels in oceans mean waters have relatively fewer carbonate ions, which oysters, clams, corals, plankton and more rely on to build shells and other structures — and if those creatures struggle or die in acidic waters, it can have ripple effects threatening salmon, whales and other predators across the food chain, NOAA says.

The scientists blamed acidification on the fact that oceans are absorbing carbon dioxide from the Earth’s atmosphere, including emissions that humans create by burning fossil fuels in power plants, cars and more.

To figure out how much the water chemistry off California has changed in the last century, scientists zeroed in on an underwater protist that can be used to track acidification shifts over time.

Dead single-celled foraminifera drift to the bottom of the ocean each day and then get covered up by sediment, researchers said. And the composition of those tiny organisms’ shells, which are buried at sea, offers a peek into how ocean conditions have changed year by year, because researchers can compare layer upon layer of microscopic shells.

“By measuring the thickness of the shells, we can provide a very accurate estimate of the ocean’s acidity level when the foraminifera were alive,” lead study author Emily Osborne of NOAA said in a statement.

A foraminifera shell magnified to 650 times its actul size under a scanning electron microscope. NOAA

The researchers said they analyzed nearly 2,000 shells dating back to 1895, which Osborne started gathering from sediment off the Southern California coast in 2013, the Oregonian reported.

According to NOAA researchers, “These colorful spots are tiny foraminifera shells taken from the mud of core samples as seen under a microscope.” NOAA

Those shells didn’t just reveals an acidification trends linked to climate change — they also showed that acidification is worsening in a cyclical pattern that tracks with Pacific Decadal Oscillation, a phenomenon researchers described as “a natural warming and cooling cycle” in ocean waters.

“During the cool phases of the Pacific Decadal Oscillation, strengthened winds across the ocean drive carbon dioxide-rich waters upward toward the surface along the West Coast of the U.S.,” Osborne, who works in NOAA’s Ocean Acidification Program, said in a statement. “It’s like a double whammy, increasing ocean acidification in this region of the world.”

NOAA characterizes Pacific Decadal Oscillation as “a long-lived El Niño-like pattern of Pacific climate variability” with extremes “marked by widespread variations in the Pacific Basin and the North American climate.”

Researchers said the findings fill a void in the historical data about the impacts of climate change on ocean acidification off the West Coast.

According to the Los Angeles Times, “scientists for years have worried that the West Coast would face some of the earliest, most severe changes in ocean carbon chemistry. Many have noted how West Coast waters seemed to acidify faster, but there was little historical data to turn to.”

The new study is providing that data.

“This is the first time that we have any sort of record that takes it back to the beginning of the [last] century,” Osborn said, per the Times. “Prior to this, we didn’t have a time series that was long enough to really reveal the relationship between ocean acidification” and climate cycles.

According to the Oregonian, a 2015 Oregon State University survey of shellfish farmers revealed that three-quarters “reported some level of concern over ocean acidification. Of those respondents who said they have been affected by ocean acidification, 97 percent reported financial damage, while 68 percent cited emotional stress.”

Oceans absorb roughly 30 percent of carbon dioxide released in the atmosphere, according to NOAA.

“While the ocean has served a very important role in mitigating climate change by absorbing CO2 from the atmosphere, there’s a capacity at which the ocean can’t absorb anymore,” Osborne said, according to the Times. “From this study, and so many other published studies, there’s no question that the answer is to curb our carbon emissions.”

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