An unusual bloom of toxic algae has closed a third of Maine’s coastline to clam and mussel harvesting and triggered a widespread shellfish recall.

Last week, the Department of Marine Resources issued a recall of mussels, clams and quahogs caught in Down East Maine after samples tested positive for domoic acid, a biotoxin that can cause illness, memory loss, brain damage and possibly death in humans.

At the same time, the state banned harvesting for mussels, clams, oysters and carnivorous snails on parts of a wide swath of coastline from Deer Isle to the Canadian border.

This is the first time an algae bloom producing toxic domoic acid has occurred in Maine, although low levels of the toxin have been found in shellfish for decades. Some recent mussels and clams showed domoic acid levels of up to 100 parts per million, five times the level considered safe for human consumption.

“A closure for this toxin in eastern Maine is unprecedented, that is not anything anyone has ever seen,” said Darcie Couture, a Brunswick marine scientist and former head of the state’s marine biotoxin program.

“No one on this coast is that experienced with a domoic acid event,” Couture said. “I don’t think it is sinking in how serious this is.”

The Department of Marine Resources isn’t sure what triggered the bloom, how long it will last, or what other species might be affected. This week it started precautionary testing on quahog, Jonah and rock crabs, urchin, whelk and lobster in the affected area.

“We don’t have any science that specifically points to anything,” said DMR spokesman Jeff Nichols. “Our focus really is on the public health side of this and we are ensuring the closure is implemented and enforced. So far that has been working.”

FIVE TONS OF SHELLFISH RECALLED

The recall affected mussels and quahogs harvested and stored around Jonesport and clams harvested from Gouldsboro to Jonesport. About five tons of shellfish, 96 percent of the affected product, were successfully recalled, Nichols said. The recall affected five Maine companies, and contaminated mussels made it to retail stores in Georgia, Massachusetts, Missouri, New Jersey, New York and Utah, the DMR said. Soft-shelled clams were found only in Maine and mahogany quahogs were limited to Massachusetts. There is no way to trace the product that wasn’t recovered because it was not sold through retail outlets, Nichols said.

There have been no reported illnesses from the contaminated shellfish, the department said.

The recall and closures have been a financial blow to Down East harvesters and shellfish dealers.

“Anytime there is something in the news about the safety of shellfish, it affects the market,” said Albert Carver, who owns A.C. Inc., a shellfish dealer in Beals. He would not specifically say how much product was affected, but the financial impact was “significant.” This is the first recall Carver has had in 40 years of doing business.

Dealers and harvesters are accustomed to closures, usually for toxic algae blooms known as red tide that can cause paralytic shellfish poisoning. But no one is sure what to expect this time around, Carver said.

“Generally we get closed for red tide, the state of Maine is extra good at predicting that,” Carver said. “This is new, it is a different critter, it affects things differently, we don’t have any history of it.”

Domoic acid is produced by a marine phytoplankton called Pseudo-nitzschia that grows rapidly, or blooms, under the right environmental conditions. Filter feeders like mussels and clams eat the algae and store the toxin. The toxin can work its way into the food chain, poisoning other fish, crustaceans, seabirds and marine mammals.

‘IT IS A VERY NASTY TOXIN’

In humans, domoic acid can cause Amnesic Shellfish Poisoning, or ASP, named for the short-term memory loss it produces. Early symptoms of ASP include vomiting, nausea and diarrhea, but it can progress to severe problems such as dizziness, confusion, motor weakness, respiratory problems, coma and even death. An ASP outbreak in Prince Edward Island, Canada, in 1987 killed three people and sickened more than 100.

“It’s a serious issue, it requires attention,” said Sandra Shumway, a shellfish expert at the University of Connecticut. “If it is showing up in those high numbers, I’d be worried. It is a very nasty toxin.”

While Maine has little experience with domoic acid, states on the Pacific Coast are familiar with the problem. A bloom last year stretched from central California to Washington and into Alaska. The bloom involved some of the highest domoic acid concentrations ever observed in Monterey Bay and the central Oregon coast, according to the National Oceanic and Atmospheric Administration’s northwest fisheries office.

The high readings forced an early closure of the razor clam industry in Washington and Oregon last year. Tests in one area in Washington showed toxin levels of 170 parts per million in clams, more than eight times the level considered safe for human consumption. Washington shut down most of its lucrative Dungeness crab fishery last summer because the crustaceans tested at high toxin levels.

In Maine, the state regularly tests shellfish at 80 monitoring sites and updates its closure maps. Currently, mussels, carnivorous snails and surf clams are closed from Deer Isle to the Canadian border. All other clams are closed from Bar Harbor to the border, and European oysters are closed from Deer Isle to Machiasport, said Nichols, the DMR spokesman.

In order to open an area, there needs to be two clean shellfish meat samples, less than 20 parts per million, recorded seven days apart.

“There is no set timeline for this,” Nichols said. “We just continue to rigorously monitor the coast. We don’t know how long this is going to last.”