The Maine Department of Marine Resources has given the all-clear for Down East shellfish harvesters, more than a month after closing the region to harvesting because of an unusual bloom of toxic algae.

On Monday, the DMR announced it was reopening harvesting areas between Penobscot Bay and Machiasport for shellfish, including softshell clams and mussels. Areas farther east, between Machiasport and Calais, were reopened to harvesting Oct. 25.

The entire Down East coast from east Penobscot Bay to the Canadian border was closed at the end of September. The closure was triggered after shellfish samples from Jonesport, Corea and Roque Bluffs tested positive for elevated levels of domoic acid, a biotoxin that can cause amnesic shellfish poisoning and lead to illness, brain damage and possibly death. About 5 tons of softshell clams, mussels and quahogs harvested in the affected area were recalled in late September and destroyed. The products had been distributed as far as Missouri and Utah.

The acid can be produced by a bloom of Pseudo-nitzschia, a naturally occurring phytoplankton. Different Pseudo-nitzschia species are commonly found in the Gulf of Maine, but this is the first recorded bloom that has created toxic levels of domoic acid, according to the Department of Marine Resources. Shellfish eat the plankton and store the toxin.

Maine has more experience with harmful algae blooms – called red tide – caused by Alexandrium, a different phytoplankton that produces a toxin that can cause paralytic shellfish poisoning.

Department scientists and researchers are still unclear what caused a toxic Pseudo-nitzschia bloom, but have said preliminary results from testing by the Woods Hole Oceanography Institute and Bigelow Laboratory for Ocean Sciences indicate a species of the phytoplankton previously undocumented in the Gulf of Maine could explain the toxicity.

Last month, Rhode Island closed most of its shellfish harvesting areas because of a Pseudo-nitzschia bloom, and large parts of the Massachusetts coastline south of Cape Code also were shuttered. Both states reopened their harvesting zones last week.

The U.S. Food and Drug Administration has an action level of 20 parts per million of domoic acid in shellfish. The agency will take action to remove products with levels of contaminants above that limit. The state uses the same limit to determine if it should close harvesting areas.

During the bloom, some tested shellfish had domoic acid levels of 129 parts per million, according to the Department of Marine Resources.

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

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