Scientists say the toxic algae bloom off the West Coast could be the largest ever recorded. It stretches 40 miles wide and 650 feet deep from central California to Alaska.
Vera Trainer, a researcher with the Northwest Fisheries Science Center in Seattle, says, "It's one the most geographically extensive, long lasting and most toxic harmful algal blooms of this type that we've seen on the U.S. West Coast."
Trainer is part of a team currently on a research cruise aboard a National Oceanic Atmospheric Administration (NOAA) vessel conducting a fish survey from Canada to San Diego.
The naked eye can barely see the bloom, but in dense sections it might add a slightly brown-green tinge to the water.
It produces a powerful neurotoxin, domoic acid, that accumulates in small marine life that feed on algae. Mammals and birds that prey on small fish can in turn get sick.
Trainer urges great caution to avoid contaminated seafood. "You can become quite sick," she says. "You have nausea, vomiting, and in very extreme cases you have permanent short term memory loss, or can even die."
Raphael Kudela, professor of ocean sciences at University of California Santa Cruz, says several commercial fisheries along the coast have already closed.
"Dungeness crabs is closed, anchovies are closed over quite a bit of the California coast. Razor clams are closed in Washington and Oregon."
But, state officials say shellfish purchased in stores is safe because it's regularly tested for toxins. However, officials warn against eating recreationally caught clams, mussels and crab from Monterey, Santa Cruz or Santa Barbara counties. And, they recommend avoiding commercially or recreationally caught anchovies or sardines from infected waters.
The bloom is thriving in unusually warm, still summer waters.
Trainer says algae blooms are becoming more and more common, and the increase could be related to global climate change.
"Whether this bloom is providing a window of things to come for the future, and a world that we can envision under climate change, I think that's a distinct possibility," says Trainer.
Historically, toxic algae blooms usually disappear a few weeks after they appear. But, this one has lasted since May.
Trainer expects the bloom to stick around until fall storms shake up the ocean and wash it away.