By Sarah Harrison, WIRED

In Washington state, scientists, coastal communities, and state agencies are banding together to manage the growing threat of harmful algal blooms.

IN 1991, FRANK Cox, a biotoxin coordinator for the Washington State Department of Health, went digging for razor clams. He packed up his haul and sent the shellfish to a state lab to check for paralytic shellfish poisoning, the only marine toxin known to appear on that part of the coast.

The lab ground up the shellfish and mixed the tissue with solvents. Then, they injected the slurry into mice, a common testing technique at the time. But the mice started to do something peculiar. Instead of gasping for breath or dying—standard symptoms of paralytic shellfish poisoning—the mice started scratching behind their ears. The symptom, though seemingly innocuous, revealed a disturbing new toxic threat: Domoic acid had arrived on the West Coast.

Domoic acid is a deadly, naturally occurring neurotoxin produced by Pseudo-nitzschia, a genus of planktonic diatom or single-celled algae. When that algae is eaten by other marine animals, like mussels, clams, and Dungeness crabs, the acid concentrates in their digestive tracts and internal organs. And when those tasty marine treats are ingested by humans, the domoic acid can make people sick, causing headaches, stomach cramps, nausea, and diarrhea. In more severe cases, patients might also experience seizures, coma, and even short-term memory loss, which is why the illness is also sometimes referred to as amnesic shellfish poisoning. After the world’s first occurrence of domoic acid poisoning in 1987, three people died.

So when state officials found out what was happening in those mice in the lab in Washington, they quickly closed the entire state’s coastline. Electronic signs on the highway warned visitors away from clamming, and the Washington Department of Fish and Wildlife sent armed officers to patrol the beaches. “The public didn’t know what the heck was going on,” says Vera Trainer, an oceanographer at the National Oceanic and Atmospheric Administration (NOAA) who studies harmful algal blooms in the Pacific Northwest.