A long band of toxic algae blooming off the West Coast of the United States shows no sign of receding months after scientists first observed it, leaving many worried that it will make trouble for local commercial fishing and tourism industries.

In this undated handout microscopy photo provided by NOAA Fisheries, the algae pseudo-nitzchia, which produces the toxic domoic acid, is seen from an algae bloom sample collected during its survey this summer on the West Coast.

Some species of algae in the bloom—part of a group called called Pseudo-nitzschia, produce a toxin known as domoic acid, which can harm or even kill seabirds, mammals and humans. There's still a lot about the algae bloom that scientists don't understand—but some of what they have learned has them concerned.



Among their concerns is the possibility that an unusually strong El Nino climate pattern—such as the one that's expected this year—will keep water temperatures in the Pacific Ocean unusually high through next year, meaning the toxic bloom could last through 2016, said Raphael Kudela, a professor of ocean ecology at the University of California Santa Cruz.

"The one that we are waiting to see is one of the strongest El Ninos ever, and those are exactly the sorts of conditions we have been having so far," Kudela said. "So we are waiting to see if next year we will have a big bloom, and that would be pretty much unprecedented to have blooms two years in a row."

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The size of the bloom and the amount of time it has lasted in the ocean are already unprecedented, according to the U.S. National Oceanic and Atmospheric Administration. It stretches across much of the West Coast of North America, from Monterey Bay off the central coast of California all the way up to the Aleutian Islands in the southern region of Alaska.

Scientists had previously believed that domoic acid was water soluble—meaning that it could be flushed out of the bodies of animals that ingested it, Kudela said.

But researchers have since observed domoic acid building up in the tissues of fish, leading scientists to doubt that notion. They also think that the toxin may be spreading to a wider array of marine life than they had previously thought was possible.

"That really suggests that it is really going to work its way through the food web," Kudela told CNBC. "It has always been assumed cleaning the fish (meant that) you'll be fine, as long as you are removing all of the viscera. Now, we are questioning that."

State health departments in California, Oregon and Washington have all issued warnings against catching or eating shellfish and plankton-eating fish such as sardines and anchovies from areas off the coast.