No one knows the origin of an algae bloom that closed hundreds of miles of Maine coastline to shellfish harvesting this fall. Or why the microscopic phytoplankton responsible for it suddenly became so bountiful in the Gulf of Maine. Or even why it produces toxins in the first place.

What is known is that a toxic bloom of Pseudo-nitzschia, a common phytoplankton, caused a recall of 58,500 pounds of blue mussels in September – only the second shellfish recall in Maine’s modern history. To prevent another recall, the state is drastically reassessing its shellfish monitoring practices.

“I’m frustrated we had another recall this year,” said Kohl Kanwit, director of public health for the Maine Department of Marine Resources. A similar Pseudo-nitzschia bloom in 2016 forced a recall and closed a third of the state’s 3,500-mile coastline to harvesting.

“I was confident we were going to be ahead of it. We knew a lot more, we were quicker to react to it, but we weren’t accounting for the fact that in less than a week toxins could go from barely detectable to over the (safety) limit.”

Next year, even a hint of toxic Pseudo-nitzschia in the water will trigger broad precautionary closures until the department knows shellfish are safe, an entirely new approach to biotoxin management, Kanwit said.

“Usually you have plenty of time,” she said. “Now, going forward into next year, the minute we start to see toxins we will start to take action. We won’t wait to see what the next week’s scores are. We will close down flats.”


On Wednesday, the state lifted a harvesting ban on a section of coastline east of Milbridge after toxin levels declined to safe levels. It was the last part of coast to reopen since elevated toxin levels were detected in Frenchman Bay almost two months ago. No illnesses were reported as a result of the September blooms, but a precautionary harvesting ban on parts of the coast from Vinalhaven to Eastport – an area with little commercial harvesting – remains in place awaiting testing.


Maine has practiced a successful shellfish safety program for more than 50 years and the state has been held up as the gold standard for monitoring and responding to bacterial and biotoxin problems.

But Maine’s biotoxin program is designed to forecast and respond to annual blooms of Alexandrium, commonly known as red tide. Red tide is fairly easy to predict and manage, Kanwit said. If there is a red tide bloom, it is guaranteed to carry saxitoxin, which causes paralytic shellfish poisoning. Red tide predictably blooms in spring and summer, creeping in gradually so monitors can manage it by testing sites on coastal headlands and closing off specific harvesting areas where the toxin exceeds safety limits.

Pseudo-nitzschia doesn’t work like red tide. It blooms suddenly and can become extremely poisonous very quickly, even at a low concentration. “They are becoming toxic at cell numbers that are so low, there is something missing here,” said Quay Dortch, the coordinator of the harmful-algae-bloom program at the National Oceanic and Atmospheric Administration. “We don’t know. That is what is so strange about Maine.”

There are about 13 species of Pseudo-nitzschia in the Gulf of Maine, said Mark Wells, a marine biology professor at the University of Maine who has studied blooms of the algae on the West Coast. Some species produce toxins while others do not. The species are so closely related that researchers need an electron microscope to tell the difference. And they are unpredictable.


“They can bloom at one time with no toxin whatsoever and bloom at another time and be extremely toxic,” Wells said. The speed with which it becomes toxic is also alarming, he said.

“… What is happening now is that (monitors) have a really short timeline to make a decision between the time they notice it and when it becomes really toxic.”

Toxic species produce domoic acid, which can cause amnesic shellfish poisoning, resulting in nausea, diarrhea and vomiting, short-term memory loss and seizures. The only recorded case of domoic acid poisoning occurred in Prince Edward Island in 1987, when three people died and more than 100 became ill after eating tainted blue mussels.

The federal action limit for domoic acid is 20 parts per million. If shellfish exceed that level, state authorities have to stop harvesting and issue a recall for any tainted product.

During the height of the Pseudo-nitzschia bloom in 2016, tests revealed mussels near Brooklin and clams near Machiasport had toxin levels more than six times the health limit. Lobster tomalley, the green paste inside the crustaceans, tested near Milbridge had almost five times the limit, according to unqualified DMR testing data.

A request for 2017 testing data was not returned by the department.



The sudden toxic blooms have alarmed monitors and scientists, but explanations are in short supply, and so is funding to get answers.

Changes in Maine waters may be driving new blooms, said Wells, the UMaine professor. The Gulf of Maine is one of the fastest-warming bodies of water on the Earth, and observers have warned about the ecological changes driven by a warming planet.

“The concern is, we are seeing the start of a trend. It might not happen every year, but it may happen more frequently than in the past,” he said.

In 2015, a massive bloom of Pseudo-nitzschia on the West Coast shut down shellfishing and the lucrative Dungeness crab fishing industry for months. That bloom was connected to a “warm blob” of ocean water pushed onshore, which favored the development of toxic species, Wells said.

“The concern is the warming of the surface waters in the Gulf of Maine might be doing the same thing, but I have to emphasize, we don’t know,” he said.


Researchers also don’t fully understand how algae blooms produce toxins, or why, said Dortch, from NOAA. Nutrients, water conditions, sunlight and multiple other environmental factors can make a bloom toxic, or not. Some think Pseudo-nitzschia may become toxic when it doesn’t have enough silica to reproduce, Dortch said.

“I think that at this point we don’t really know, it is not just the Gulf of Maine that has this problem,” she said.

And it’s not likely that additional funding for research on harmful blooms will be forthcoming anytime soon. Dortch said funding has never been sufficient for all research proposals and a 2018 budget from the Trump administration eliminates bloom research funding though NOAA.

But while funding is scarce, a scenario where there is no money to study harmful algae blooms is unlikely, said Don Anderson, director of U.S. National Office for Harmful Algal Blooms at Woods Hole Oceanographic Institution.

Scientists have become better at predicting algae blooms, even as the problem is getting worse, in coastal waters, as well as in lakes and reservoirs. Lake Erie is periodically contaminated by algae blooms, threatening drinking water for 500,000 customers in Toledo, Ohio, and sickening some people.

The upside of worsening blooms is that politicians and government agencies are taking the problem more seriously and considering support for additional research, Anderson said. Woods Hole is trying to fund a research project focused on Pseudo-nitzschia, and hopes discoveries will go beyond the science of toxic blooms and develop ways to predict blooms and avoid recalls, Anderson said.


“That is what it is very frustrating. The research that is needed is much more than ‘let’s get some money to find out why Pseudo-nitzschia blooms or doesn’t.’ It needs to get the managers what they need to deal with it.”

Peter McGuire can be contacted at 791-6325 or at:

Twitter: PeteL_McGuire

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