State officials have closed tidal areas on the east side of Mount Desert Island and issued a recall for recently harvested mussels over fears of possible shellfish poisoning.
The state Department of Marine Resources is banning the harvest of clams, oysters or carnivorous snails from Frenchman Bay and other connected bays east of Little Cranberry Island and west of Cranberry Point in Gouldsboro, according to a Thursday advisory.
The closure, effective immediately, is in response to high levels of domoic acid caused by an outbreak of a naturally occurring marine biotoxin. Harmful algal blooms, sometimes referred to as red tide, can produce toxins such as domoic acid which can cause sickness and memory loss in humans and, in severe cases, death.
The state also closed state waters, most of them further out to sea, from roughly North Haven to Machiasport. That closure, enacted as a precaution, applies to mussels, European oysters and surf or hen clams.
The department is recalling mussels that were harvested in the Frenchman Bay area between Sept. 10 and 14, Jeff Nichols, spokesman for DMR, said Friday. The department does not yet know how many mussels were harvested in that area during that time.
“We’re still working to communicate directly with dealers and we’re still trying to determine the exact amount of product impacted,” Nichols said.
Companies affected by the recall include Atlantic Shellfish and Moosabec Mussels, both of Jonesport; Eastern Maine Mussels of Hancock; Pemaquid Oyster Company of Waldoboro; and Stewardship GEM LLC of Bar Harbor, he said.
The state routinely tests shellfish along the entire coast for toxins, Nichols said. The closure will last until test results taken at least one week apart show that domoic acid levels have fallen back below the threshold of 20 parts per million, which is considered the maximum concentration safe for human consumption.
Such closures happen along the Maine coast every summer when biotoxins, which can cause amnesic shellfish poisoning or paralytic shellfish poisoning, naturally bloom in large enough quantities to pose a threat to people who eat contaminated shellfish.
Amnesic shellfish poisoning can cause gastrointestinal symptoms at first and then headaches, confusion, dizziness, disorientation or even long-term memory loss, according to state officials. In severe cases, seizures, weakness and paralysis or death may occur.
With paralytic shellfish poisoning, symptoms can include tingling of the tongue, lips and throat that then may spread to the face, neck and arms. Other symptoms can include headache or nausea, and can progress to weakness, difficulty breathing and choking.
The last confirmed cases of red tide poisoning in Maine were in 2007, 2008 and 2009, which resulted in the sickening of eight people who harvested and ate contaminated mussels.
The toxins most commonly accumulate in clams, mussels, oysters and snails. Other marine species such as lobster, crabs, scallops, shrimp and finfish generally are considered to be not at risk for contamination.
Similar biotoxin closures between the Maine/New Hampshire border and the eastern side of Penobscot Bay were repealed in August.
A closure on the harvesting of surf or hen clams off Cape Elizabeth and Scarborough remains in effect.
Clarification: An earlier version of this article misidentified a type of harmful algal bloom known as red tide as being caused by domoic acid. Red tide is caused by a type of algae that produces saxotoxin, not domoic acid.