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Smithsonian study finds more bad news about climate change: skimpier Chesapeake Bay oysters

In a lab dubbed the “room of doom” at an Edgewater research center, scientists learned that climate change is no friend to lovers of meaty oysters.

A new study by the Smithsonian Environmental Research Center shows that oysters stressed by low dissolved oxygen and warm water early in life grow thicker shells and less meat, the white, briny culinary delight the bivalve is harvested for.

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The warmer water is, the less dissolved oxygen it holds, the substance fish, oysters, crabs and underwater plants use to breathe.

In other words, oysters about half the normal size.

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SERC Scientist Emeritus Denise Breitburg said climate change has been the driving factor in the Chesapeake Bay’s low oxygen, or hypoxia, for the past 30 years. A 2018 study from the University of Maryland, Center for Environmental Science predicted that the amount of low-oxygen and no-oxygen water in the bay would increase by 10%-30% between the late 20th century and the mid-21st century.

In 2018, researchers at SERC studied thousands of oysters and their response to different temperatures and oxygen levels. The lab was dubbed the “Room of DOOM” (Dissolved Oxygen Oyster Mortality). The study based on that work was recently published.

Postdoctoral fellow Sarah Donelan took 3-month-old oysters and exposed some of them to warm water with low dissolved oxygen for 18 days.

At the end of that period, there was no difference in the oysters that had been in warm water and those which were spared. Or, so Donelan thought.

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Two months later, she took another subset and exposed them to low-oxygen and warm temperatures again. This time the oysters started to show signs of strain.

But when she opened up the oysters, she saw what the stress was really doing to them.

While the shells of the oysters looked similar, the meat of the oysters exposed to both periods of stress had a ratio of tissue to shell that was half that of other oysters.

Donelan said while two oysters might look the same on the outside, inside the amount of meat was different.

“At the raw bar, you care about how much meat is in there,” she said.

Raw Oysters at McGarveys Saloon & Oyster Bar, Friday, February 26, 2021. A new study shows that climate change could mean less meaty oysters at the raw bar.
Raw Oysters at McGarveys Saloon & Oyster Bar, Friday, February 26, 2021. A new study shows that climate change could mean less meaty oysters at the raw bar. (Paul W. Gillespie/Capital Gazette)

Donelan said while they can’t make specific recommendations from their results just yet, the study shows that low dissolved oxygen early in life continues to affect oysters later on. Some options for the future could include bubbling more dissolved oxygen into the water at oyster farmers, or more closely monitoring temperature and dissolved oxygen levels.

It is another piece to the puzzle of how multiple stressors like salinity and water quality affect oysters.

“Farmers are probably already thinking about keeping their oysters in good environments, but our results highlight that monitoring and mitigating stress exposure for young oysters is important,” Donelan said.

Breitburg said the research showed that even for something thought to be well-understood, like oysters, there is still a lot unknown.

“The problem is more complex than we were thinking,” she said.

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