Toxic Algae Bloom on West Coast May be Largest Ever

Jun 18, 2015 10:34 AM EDT

A toxic algae bloom is spreading along the West Coast, and it may be the largest one scientists have ever seen.

Federal biologists onboard a NOAA research vessel have begun a survey of the bloom - which stretches from Central California to British Columbia, and possibly as far north as Alaska - to figure out its extent and severity.

Of particular concern is the fact that the bloom contains a single-celled algae called Pseudo-nitzschia, which produces dangerous levels of domoic acid, a powerful neurotoxin.

Meanwhile, two other types of toxins rarely seen together have been observed in shellfish in Puget Sound and along the Washington coast, according to Vera Trainer, manager of the Marine Microbes and Toxins Programs at the Northwest Fisheries Science Center in Seattle. One causes paralytic shellfish poisoning (PSP) and the other leads to diarrhetic shellfish poisoning (DSP).

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"The fact that we're seeing multiple toxins at the same time, we're seeing high levels of domoic acid, and we're seeing a coastwide bloom - those are indications that this is unprecedented," Trainer told The Seattle Times.

Toxic algae blooms are actually quite common in the Pacific Ocean around this time of year; however, the size of this latest bloom is surprising.

"This is new territory for us," said Dan Ayres, coastal shellfish manager for the Washington Department of Fish and Wildlife. "We've never had to close essentially half our coast."

So to find out more, a team of scientists will be using the NOAA research vessel Bell M. Shimada to conduct a weeks-long fish survey from Vancouver Island down to Southern California. They will collect water and algae samples, measure water temperatures, and also test fish like sardines and anchovies that feed on plankton.

"By collecting data over the full West Coast with one ship, we will have a much better idea of where the bloom is, what is causing it, and why this year," University of California, Santa Cruz ocean scientist Raphael Kudela told the Times.

Its effects are especially bad in Monterey Bay, where domoic acid concentrations were 10 to 30 times normal levels back in mid-May, according to CBS News. Who knows where they are now.

Domoic acid is dangerous in large amounts to marine life, ranging from small fish and shellfish at the bottom of the food web, to the mammals and birds that ingest them. It can overstimulate the nervous system, causing animals to become lethargic or disoriented, and even seize and die.

It can also pose a threat to humans if they eat too much seafood that contains a lot of domoic acid. For example, in 2011, a family that ate mussels from Sequim Bay on the Olympic Peninsula experienced DSP poisoning, CBS noted - the first confirmed case.

The concentration of the acid itself in the water, however, is not high enough to cause harm to swimmers and surfers.

It remains to be seen what exactly is causing this record toxic bloom, but scientists suspect that this year's unseasonably high temperatures are playing a role (2014 was the hottest year yet). In addition, "The Blob" of unusually warm water that popped up in the northeastern Pacific late last year may also have a contributing role, leaving the United States with some weird weather.

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