From the air, the Pacific algal bloom doesn’t look like much of a threat: a wispy, brownish stream, snaking up along the West Coast. But it’s causing amnesia in birds, deadly seizures in sea lions, and a crippling decline in the West Coast shellfish industry. Here’s what you need to know about it, from what this bloom has to do with the drought to why these toxins could be a real threat to the homeless.
What’s causing it? The culprits are single-celled, plant-like organisms called pseudo-nitzschia, a subset of the thousands of species of algae that produce more than 50 percent of the world’s oxygen through photosynthesis. They’re a hardy variety usually found in cool, shallow oceans, where they survive on light and dissolved nutrients, including silcates, nitrates, and phosphates. “They’re sort of like the dandelions of the sea,” says Vera Trainer, who manages the Marine Biotoxin Program at the Northwest Fisheries Science Center in Seattle. “They’re always there in some low numbers, just waiting for nutrients to be resupplied to the ocean’s surface.” In most years, blooms in the eastern Pacific are contained near “hot spots” that dot the West Coast—relatively shallow and sheltered places like California’s Monterey Bay or the Channel Islands. They usually flare up in April or May as trade winds cycle nutrient-rich waters from offshore depths to the coast in a process called “upwelling,” but they fade after only a few weeks.
That makes the source of this bloom different from its cousin in the Gulf of Mexico, where fertilizers flowing from as far as Iowa are feeding a zone of algae that’s as large as New Jersey. “We’re seeing them in relatively pristine waters of the US West Coast,” Trainer explains, though she adds runoff and sewage discharge may be playing some role in the blooms off Southern California.
So just how big is this thing? Bigger than researchers have ever seen: a patchy stream that stretches from Southern California up along the Alaskan coast. The hot spot blooms that appear each spring are merging for the first time, Trainer explains. Though the combined mass has ebbed and flowed over the past four months, it hasn’t let up; her team finds algae each time they journey out to sea, with no signs of abatement soon. And it’s also unusually potent. “These are the highest levels of toxicity we’ve ever seen,” says Raphael Kudela, a professor of ocean sciences at the University of California-Santa Cruz. “It’s a truly extraordinary phenomenon.”
How deadly are these “dandelions”? The algae produce a compound called domoic acid, a type of amino acid that leads to a condition commonly known as “amnesic shellfish poisoning” in humans. Shellfish and some small fish, like sardines and anchovies, feed on the algae and concentrate the toxin in their flesh. When animals further up the food chain—like birds—eat those fish and shellfish, the domoic acid seeps into the bloodstream and eventually the brain, where it attacks cells in the hippocampus, the brain’s command center for memory and learning. The result: amnesia-stricken birds that will repeatedly fly into windows, and sea lions that writhe on the shore, plagued by seizures. Both are symptoms of rapidly firing neurons in the hippocampus, which will eventually burn out and kill the animal. Beaches have been littered with dead fish, birds, and sea lions up and down the Pacific coast since May—all the way up to Alaska, where NOAA is investigating the deaths of fin whales in connection with the toxin.
Exposing the Big Game 