Brunswick Marine Warden Dan Devereaux said Maine’s cold climate could help kill harmful algae that forced the closure of clam flats across Casco Bay recently.

Devereaux hopes shellfish harvesters can get back to work well before Christmas, although no one knows for certain when the flats could reopen.

On Dec. 4, the Maine Department of Marine Resources issued the notice of the precautionary closing, stretching from Cape Elizabeth to Harpswell. Devereaux said the closure includes Maquoit and Middle bays, the most productive clam flats in town this year.

By late Friday afternoon, the DMR had announced a mussel, clam, oyster and carnivorous snail closure in the northern part of New Meadows River, which does not include the New Meadows lakes, due to the risk of contamination by naturally occurring biotoxins.

There are between 15 and 20 locally licensed harvesters that work year-round. Brunswick is lucky, Devereaux said, because it still has shellfish coastline open on the New Meadow so harvesters can still work, at least for now. Thomas Point is scheduled to close Wednesday for conservation purposes.

Toxic bloom

According to the National Oceanic and Atmospheric Administration, harmful algae blooms “occur when colonies of algae — simple photosynthetic organisms that live in the sea and freshwater — grow out of control, while producing toxic or harmful effects on people, fish, shellfish, marine mammals, and birds.”

There are many viable shellfish on the coast of Maine that filter biotoxins at different rates, Devereaux said, “and we don’t know how these shellfish excrete these toxins and at what rate.”

“We’ve offered to assist the state in terms of collecting samples and even pitching in if it costs money to test Maquoit and Middle Bay more precisely,” he said.

Kohl Kanwit, director of the DMR Bureau of Public Health, said harmful algae blooms have been found in the Gulf of Maine the last few years, but prior closures were related more to red tide or paralytic shellfish events.

The phytoplankton that prompted this most closure is not new, Kanwit said, but prior to last year, Maine hadn’t seen any appreciable toxin in shellfish associated with it.

As of Friday, Kanwit said, “we do not know that’s what’s happening in Casco Bay.”

Shellfish can toxify faster than DMR can collect samples and process them. Any given area could see a threeto four-week closure, according to Kanwit.

In terms of losing access to harvesting opportunities, she said, “I don’t think that this is going to go away.”

Kanwit said Maine has a robust program for catching these blooms, knowing potentially toxic species and making closures to protect public health.

“Confidence in Maine shellfish is safe,” Kanwit said.