The state has closed all Dartmouth waters to shellfishing due to the detection of life-threatening algae in Buzzards Bay waters.

The Massachusetts Division of Marine Fisheries has banned shellfish harvesting following a burst in algae contamination. The state division first detected paralytic shellfish poisoning algae, which not only can lead to discolored waters, but can contaminate filter-feeding shellfish with life threatening toxins. Now, testing results are showing extremely high concentrations of pseudo-nitzschia, which can cause amnesic shellfish poisoning in humans.

In mild cases of amnesic shellfish poisoning, symptoms — including nausea, vomiting, diarrhea and abdominal cramps — arise within 24 hours of consumption of contaminated shellfish. In more severe cases, neurological symptoms occur, including headaches, hallucinations, confusion, short-term memory loss, respiratory difficulty, seizures, coma, and, in extreme cases, death.

Paralytic Shellfish Poisoning (PSP) can occur if shellfish are consumed. Symptoms — which include tingling, numbness, and burning of the perioral region, ataxia, giddiness, drowsiness, fever, rash, and staggering — are purely neurological and their onset is rapid. The most severe cases result in respiratory arrest within 24 hours of consumption of the toxic shellfish. There is no antidote. In non-lethal cases, the effects last a few days.

Harbormaster Steve Melo said luckily, neither have been spotted in Dartmouth.

"I've never heard of it before in Buzzards Bay," said Melo. Amnesic shellfish poisoning was first recorded off the eastern coast of Canada in 1987 when three deaths and more than 100 confirmed cases of acute intoxications followed the consumption of cultured mussels.

Due to the rains and the resulting increase in nitrogen pollution, shellfishing had already been closed, Melo said.

"It's discouraging with all our efforts to improve and expand shellfishing in Dartmouth. It's a reminder that Mother Nature is still in charge," said Melo.

Melo said the state is doing daily testing, as the algae blooms have been found in Rhode Island, Nantucket, and Cape Cod. "It's good to know the Division of Marine Fisheries is on top of it," he said.

Large-scale, proactive monitoring programs (assessing toxin levels in mussels, oysters, scallops, clams) and rapid harvesting closures are the best prevention method, according to authorities.

As a result of the closure, digging, harvesting, collecting and/or attempting to dig, harvest or collect shellfish, and the possession of shellfish, is prohibited in Bourne, Dartmouth, Fairhaven, Falmouth, Gosnold, Marion, Mattapoisett, New Bedford, Swansea and Westport.

Excluded from the ban are bay scallop and conch (welk) harvesting, in which the digestive tract is not ingested by humans.

Melo said the shellfish will eventually clean themselves of any toxins, and that it is just a matter of waiting.