SEATTLE — A vast bloom of toxic algae off the West Coast is denser, more widespread and deeper than scientists feared even weeks ago, according to surveyors aboard a National Oceanic and Atmospheric Administration research vessel.
This coastal ribbon of microscopic algae, up to 64 kilometres wide and 200 metres deep in places, is flourishing amid unusually warm Pacific Ocean temperatures. It now stretches from at least California to Alaska and has shut down lucrative fisheries. Shellfish managers on Tuesday doubled the area off Washington’s coast that is closed to Dungeness crab fishing, after finding elevated levels of marine toxins in tested crab meat.
So-called “red tides” are cyclical and have happened many times before, but ocean researchers say this one is much larger and persisting much longer, with higher levels of neurotoxins bringing severe consequences for the Pacific seafood industry, coastal tourism and marine ecosystems.
Dan Ayres, coastal shellfish manager for the Washington Department of Fish and Wildlife, said the area now closed to crab fishing includes more than half the state’s 252-km-long coast, and likely will bring a premature end to this year’s coastal crab season.
“We think it’s just sitting and lingering out there,” said Anthony Odell, a University of Washington research analyst who is part of a NOAA-led team surveying the harmful algae bloom, which was first detected in May. “It’s farther offshore, but it’s still there.”
The survey data should provide a clearer picture of what is causing the bloom which is brownish in colour, unlike the blue and green algae found in polluted freshwater lakes. Marine detectives already have a suspect: a large patch of water running as much as 3 degrees centigrade warmer than normal in the northeast Pacific Ocean, nicknamed “the blob.”
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The brownish bloom was particularly thick off the coast of Santa Barbara, California, and Odell said it was unusually dominated by one type of algae called Pseudo-nitzschia, which can produce the neurotoxin domoic acid.
“It’s an indication of an imbalance,” said Vera Trainer, a research oceanographer with the Northwest Fisheries Science Center in Seattle. “Too much of any one thing is not healthy for anybody to eat.”
Trainer said this bloom is the worst she’s seen in 20 years of studying them. Harmful algal blooms have usually been limited to one area of the ocean or another, and have disappeared after a few weeks. This one has grown for months, waxing and waning but never going away.
This is really unprecedented territory for us
Full article: Red tide: Massive, ‘incredibly thick’ toxic algae bloom in Pacific now stretches from California to Alaska (Vancouver Sun)
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