Influx of toxic algae blooms along U.S. west coast due to climate change, scientists conclude

SEATTLE — Due to warming ocean temperatures, more and more toxic algal blooms (Pseudo-nitzschia algae) are being seen on the west coast of the United States. These algae create a neurotoxin known as domoic acid that can wreak havoc on the digestive and neurological systems of humans and animals alike.

As one can imagine, this development is anything but positive for west coast shellfish harvests.

“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,” says lead author Dr. Vera L Trainer from the U.S. National Oceanic and Atmospheric Administration (NOAA) in Seattle in a media release. “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.”

Dr. Trainer has been researching domoic acid in both shellfish and water samples from the west coast since 1998. Fast forward to 2015, and a heatwave in the northeast Pacific Ocean led to unprecedented amounts of harmful algal blooms. That year saw shellfish harvesting called off altogether and staggering marine mammal casualties. Furthermore, one specific coastal area located in northern California by the Oregon border is still a toxic “hotspot” to this day with shellfish harvesting indefinitely banned.

Toxic algae blooms are a growing danger in the oceans

Researchers’ calculations find the 2013-2015 heatwave was five times more likely to be due to climate change than natural causes. Also, future extreme marine heatwaves are currently 20 times more likely to occur than they would have been without man-made climate change. Those predictions are based on extensive datasets including decades worth of temperature data and wind and ocean current measurements.

Thanks to the very nature of its water currents and coastal topography, the coastal area near the California/Oregon border is an ideal environment for more algal blooms. In areas like this, Pseudo-nitzschia algae stays buried under sediment for years until ocean swells bring it to the surface. That’s when warm temperatures cause the algae to multiply.

In an effort to combat this problem, a number of local organizations (NOAA, the University of Washington, the Washington State Departments of Health and Fish and Wildlife and Native Tribes) have come together to start issuing algae forecasts that warn locals when it is and isn’t safe to harvest shellfish.

“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,” Dr. Trainer concludes. “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 Frontiers in Climate.

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