Algal bloom in Lake Binder, Iowa. (Photo Credit: Dr. Jennifer L. Graham / U.S. Geological Survey)

Algal bloom in Lake Binder, Iowa. (Photo Credit: Dr. Jennifer L. Graham / U.S. Geological Survey)

Toxic algae that has been growing rapidly in Monterey Bay since May continues to plague fisheries as scientists attempt to understand what has made this algae bloom one of the largest and most severe in the last decade.

Algae blooms — a spurt of microscopic algal growth caused by elevated levels of nutrients and warm, still waters — have been documented in Monterey Bay for the last 25 years. But this one is unusual in its scope—stretching from Santa Barabara to as far north as Alaska — and in the high levels of toxins released by the microscopic organisms.

The organism Pseudo-nitzschia is the primary culprit of the bloom. It’s a single-celled organism that produces the neurotoxin domoic acid.

Pseudo-nitzschia seriata. (Image Credit: Minami Himemiya)

Pseudo-nitzschia seriata. (Image Credit: Minami Himemiya)

In May, sensors deployed by the National Center for Coastal Ocean Science’s detected early signs of the toxin in the Monterey Bay. Even then, the levels of domoic acid found were above the limit deemed safe for eating seafood, and the California Department of Health closed some anchovy, sardine and crab fisheries and advised consumers not to eat recreationally-harvested mussels and clams from Monterey Bay. Since then, numerous fisheries in Washington, Oregon and elsewhere in California have been closed.

“It’s a pretty massive bloom,” Raphael Kudela, a professor of ocean sciences at the University of California, Santa Cruz, said in a statement. “This event may be related to the unusually warm water conditions we’ve been having, and this year that warm water has spread all along the west coast, from Washington to southern California.”

Kudela is leading a project to study the bloom in Monterey Bay. The project is funded in part by the National Oceanic and Atmospheric Administration, and the NOAA Fisheries’ Northwest Fisheries Science Center in Seattle recently sent additional scientists to chart and monitor the algal bloom further north along the Pacific coast.

“The better we understand what’s happening out on the water, the better we can address the impacts,” Eileen Sobeck, an assistant administrator for NOAA Fisheries, said in a statement. “This is unprecedented in terms of the extent and magnitude of this harmful algal bloom and the warm water conditions we’re seeing offshore,” Vera Trainer, manager of the Marine Microbes and Toxins Program at the Northwest Fisheries Science Center in Seattle, added.

Scientists think a number of conditions are causing this bloom to be particularly large and potent. Ocean upwelling, which distributes colder water from deeper in the ocean to the warmer surface, has been weak in Monterey Bay. In addition, Kudela said there is a condition in Monterrey Bay, which has been dubbed the “warm blob,” where warm water has just been sitting near the coast.

While the amount of domoic acid in the water is not high enough to harm people swimming in the bay, animal rescue centers have reported an increase in sea lion, dolphin and pelican deaths.

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