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Climate change fuels new toxic algal blooms along Pacific Coast

Pseudo-nitzschia algae blooms, which produce a neurotoxin called domoic acid, have become increasingly common along the Pacific Coast. Photo by Rozalind Jester/Florida Southwestern State College
Pseudo-nitzschia algae blooms, which produce a neurotoxin called domoic acid, have become increasingly common along the Pacific Coast. Photo by Rozalind Jester/Florida Southwestern State College

Dec. 14 (UPI) -- According to a new study, a new kind of algal bloom is becoming more common along the West Coast -- fueled by human-caused climate change.

Red tides, masses of phytoplankton and dinoflagellates that tun the ocean a rusty, reddish orange, have long plagued the shores of California, but a previously rare rare type of bloom, which releases a neurotoxin called domoic acid, is increasingly putting fishers, swimmers and seafood at risk.

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On Monday, researchers published a new study in the journal Frontiers in Climate, detailing the threat of domoic acid and other algal toxins.

"This study shows that climate change can influence the occurrence and intensity of some harmful algal blooms, HABs, by creating new seed beds for their survival and distribution," study lead author Vera Trainer said in a news release.

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"Coastal communities, including Native Tribes, will suffer from the effects of HABs more frequently in the future, illustrating the importance of early warning systems such as Harmful Algal Bloom Bulletins that are becoming operational in the US and other parts of the world," said Trainer, a researcher at the National Oceanic and Atmospheric Administration.

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For more than two decades, Trainer and her colleagues have been measuring domoic acid concentrations in ocean water and seafood samples along the West Coast.

In 2015, the algae that produced domoic acid, Pseudo-nitzschia, proliferated throughout the Northeast Pacific. Fueled by a severe ocean heatwave, the toxic bloom triggered widespread marine mammal mortalities.

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As highlighted by the new research, massive blooms can turn a rare phenomena into an endemic problem.

In the wake of the 2015 bloom, domoic acid has become a persistent threat among the waters along the shores of northern California and southern Oregon. Shellfish harvests in the region has been disrupted by Pseudo-nitzschia blooms each of the last five years.

Scientists have previously used models to suss out the roles temperature, wind and ocean currents play in generating and sustaining extreme heatwaves.

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Simulations showed climate change made the marine heatwave that plagued the Pacific Coast between 2013 and 2015 five times more likely to occur under modern climate conditions than it would have been in a world without human-caused climate change. The same models suggest extreme heatwaves will be up to 20 times more likely in the near future.

For the new study, researchers examined the ways ocean currents and coastal topography make the waters off the coast of northern California and southern Oregon especially susceptible to recurring algal blooms.

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Their analysis showed Pseudo-nitzschia algae can lie dormant in marine sediments, becoming reanimated by upwelling that brings deeper water to the surface.

Massive algal blooms ensure a reserve of algae cells remain in coastal sediments, putting the region at greater risk of future toxic blooms.

Researchers at NOAA are currently working with an array of regional partners, including the University of Washington, the Washington State Departments of Health and Fish and Wildlife and Native Tribes, to monitor and forecast the risk of Pseudo-nitzschia blooms and their impact on local shellfish harvests.

"There is evidence that bacteria associated with seagrasses have algicidal properties, indicating that seagrass planting may be used to successfully control some HABs in Puget Sound," said Trainer. "But for large-scale marine HABs, early warning is our best defense and these HAB Bulletins will help preserve a way of life that includes wild shellfish harvest, on which coastal people depend."

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