Tests on dead or dying marine wildlife show the animals were exposed to a vast bloom of toxic algae that flourished off the West Coast this summer, federal biologists said on Tuesday.
Scientists detected domoic acid — a neurotoxin produced by marine algae and harmful to people, fish and marine life — in more than three dozen animals from Washington to California, including whales, dolphins, seabirds and seals. Several were found to have dangerous levels of the toxin, the National Oceanic and Atmospheric Administration (NOAA) said.
Meanwhile, high levels of domoic acid continue to be found in shellfish.
On Tuesday, California health officials advised people not to eat Dungeness or Rock crabs caught between the Oregon border and the southern Santa Barbara County line because tests showed dangerous levels of domoic acid.
Oregon state officials also issued an advisory Tuesday for all recreationally caught crab along the southern Oregon coast, from south of Coos Bay to California. Officials warned people to remove the viscera, or guts, before eating the crab meat.
Last month, Washington shellfish managers postponed the fall start of razor clam digging on ocean beaches and all razor clamming remains closed along the entire Oregon coast because of high level of domoic acid.
The toxic algae bloom emerged last spring and flourished during the summer amid unusually warm Pacific Ocean temperatures. It was the largest and most widespread ever recorded on the West Coast and shut down lucrative fisheries, according to NOAA.
Sea lions in California commonly experienced seizures, a common sign of domoic acid poisoning, during harmful algae blooms along that state's coast.
But this was the first year that such harmful effects were documented as far north as Washington state, said Kathi Lefebvre, a research biologist with the NOAA's Northwest Fisheries Science Center in Seattle.
"My biggest concern is — what does the future hold?" she asked.
Domoic acid accumulates in anchovies, sardines and other small fish as well as shellfish that eat the algae. Marine mammals and fish-eating birds in turn can get sick from eating the contaminated fish. In people, it can trigger amnesic shellfish poisoning, which can cause permanent loss of short-term memory in severe cases.
Health officials stress that seafood bought in stores is still safe to eat because it is regularly tested.
Researchers said the number of animals found exposed to domoic acid may be a small fraction of those affected since many others don't wash ashore or aren't found.