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Oyster populations at risk as climate change transforms ocean ecosystems

"They are very sensitive to changes in climate and water quality, because they cannot move if a location becomes inhospitable," researcher Yoann Thomas said.

By Brooks Hays
Oyster populations at risk as climate change transforms ocean ecosystems
An increase in warmer, wetter winters will threaten oysters, according to a new study. Photo by Pixabay/CC

Oct. 9 (UPI) -- Oyster populations are likely to suffer, accelerating mortality rates as the effects of climate change progress, according to a new study.

The research, published Tuesday in the journal Environmental Research Letters, suggests climate change -- and its effects on regional climate variability, including an uptick in wet, warm winters -- are likely to disrupt marine ecosystems and negatively impact oysters.

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To project how climate change might effect global oyster populations, scientists looked at the impacts of climate variation on the oyster mortality along the French Atlantic coast.

While surveying oyster population data collected between 1993 and 2015, researchers found mortality rates increased in years following wet, warm winters.

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Scientists linked the spikes in oyster mortality with the North Atlantic Oscillation, a weather circulation pattern in the North Atlantic. The NAO is linked with an increase in winter storms across Europe.

For many oysters, the disrupting effects of the weather circulation pattern proved fatal -- evidence of the bivalve's sensitivity to climatic variability.

Researchers believe the NAO affects oysters several different ways. By moderating temperatures, the climate pattern may allow a larger pathogen load to survive the winter. An increase in precipitation causes an influx of fresh water on the coast, lowering salinity levels. Warmer, shorter winters offer oysters less time for their off-season rest.

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In many places, scientists expect climate change to trigger an increase in warm, wet winters, a pattern that could harm oyster populations, as well as species that rely on the bivalves for food and other ecological services.

"Benthic species like oysters are keystone species in coastal ecosystems," Yoann Thomas, from the French National Research Institute for Sustainable Development, said in a news release. "For example, they build reef habitats, which sustain a high biodiversity, and provide tremendous food source worldwide though fishing or aquaculture activities."

"But they are very sensitive to changes in climate and water quality, because they cannot move if a location becomes inhospitable," Thomas said. "In this sense, oyster populations are sentinels of long-term climate fluctuations and climate trends, and more broadly of the 'health' of coastal ecosystems."

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The only solution, according to Thomas, is to drastically reduce greenhouse gas emissions and slow warming trends.

"The near-future looks bleak, but we show that this will be even worse without a clear reduction of the greenhouse gases emissions by human activities," he said. "We obviously need to take rapid action now to avoid further damage to very sensitive and vulnerable coastal ecosystems."

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