Toxic algal blooms will become more frequent off the U.S. west coast

Toxic algal blooms will become more frequent off the U.S. west coast. Rising ocean temperatures are increasing the frequency of algal blooms off the western coast of the United States, including one type of bloom that is extremely toxic, according to a new study published by Frontiers. The algae produce domoic acid, a neurotoxin that is the cause of amnesic shellfish poisoning (ASP). 

In both humans and animals, domoic acid exposure can lead to short-term memory loss and brain damage, and severe cases can be fatal. 

“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,” said lead author Dr. Vera L Trainer of the National Oceanic and Atmospheric Administration (NOAA). Toxic algal blooms will become more frequent off the U.S. west coast

“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 U.S. and other parts of the world.”

In 1998, Dr. Trainer and her colleagues began monitoring domoic acid, which is produced by Pseudo-nitzschia algae. The team collected shellfish and seawater samples along the West Coast.

A severe heatwave in the northeast Pacific Ocean in 2015 triggered a record-breaking Pseudo-nitzschia bloom that closed shellfish harvest and caused widespread marine mammal mortalities. Since then, a region in northern California near the Oregon border has become a new toxic hotspot that has prevented shellfish harvest.

Using multi-model datasets, the scientists found that the 2015 heatwave was five times more likely to have been caused by human influences rather than natural effects. 

Climate models that are based on several decades of relevant data predict that extreme marine heatwaves are now 20 times more likely to occur than they were before human-driven climate change. 

Ocean conditions in areas near the border of California and Oregon are favorable for recurring algal blooms, and the scientists have flagged them as what is known as “retentive regions.” Across these sites, Pseudo-nitzschia can remain dormant in sediments for years until ocean upwelling brings the algal cells to the surface and temperatures become warm enough for the algae to multiply.

In response to the issue of more frequent algal blooms, NOAA, the University of Washington, and several government agencies have teamed up to create the Pacific Northwest Harmful Algal Bloom Bulletin to forecast these events. The warning system will inform local communities of when and where it is safe to collect shellfish. 

Dr. Trainer’s team has found that these bulletins have become a cost-effective tool to help minimize the health and economic threats of the algal blooms.

“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 Dr. 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.”

The study is published in the journal Frontiers in Climate.

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By Chrissy Sexton, Earth.com Staff Writer