The closure of Nantucket Sound to shellfishing will continue at least through Nov. 1, Chatham's shellfish warden announced late Thursday.
In an email, Shellfish Constable Renee Gagne wrote, "The MA Division of Marine Fisheries has issued an update to local authorities indicating that the current shellfish area closures will continue, at minimum, through Nov. 1. New information indicates the possible release of harmful bio-toxins as the current algae bloom decays. The town will continue to update the public as further information is released."
The information came in a call from the biologist covering this area, she said.
This story will be updated as more information becomes available.
A potentially toxic plankton bloom prompted state officials to close all of Nantucket Sound to shellfishing last week.
As of Thursday the closure remained in place, and officials said they could not predict when it would be lifted. While initial results of tests on samples of shellfish meats did not show the presence of toxins, analysis of water samples indicated that the phytoplankton responsible for the toxins was present.
The closure includes all of the waters along Nantucket Sound east to the eastern tip of Morris Island in Chatham. The Southway and the entire east coast of Chatham remain open to shellfishing.
The closures encompasses all of the flats, bays and embayments along the south coast of Cape Cod. Closed areas in Chatham include Stage Harbor, Mill Pond, Mitchell River, Forest Beach, Cockle Cove Beach and Ridgevale Beach, some of which were already under seasonal closures. In Harwich, the Herring River, Allen Harbor and Oyster Creek, Wychmere Harbor, Saquatucket channel and all Nantucket Sound-facing beaches were closed.
Most Chatham commercial shellfishermen are working in the Southway or along the east coast and therefore unaffected by the closure, said Jamie Bassett, chairman of the town's shellfish advisory committee. Those areas are flushed by the Atlantic twice a day, which accounts for the high quality of Chatham shellfish, he said.
“Chatham shellfishermen are working,” he said.
The exception to that is the Chatham Shellfish Company, which farms oysters in Oyster River. The closure, implemented on Oct. 11, shut down the operation.
Stephen Wright said samples of oysters from the Chatham Shellfish Company's growing areas were given to state officials on Tuesday. Previous samples taken there showed “zero toxicity,” he said.
“We're hoping that remains the case.”
The shutdown creates a backlog in the regimented process of harvest and relocated oysters, he said. “It creates a little bit of a bottleneck as far as our ability to free up equipment, to bring along the seed that we have,” he said, adding that the company continued to pay its employees during the closure.
The state division of marine fisheries banned shellfish harvesting in Buzzards Bay on Oct. 7 because of a “substantial bloom” of a potentially toxic form of phytoplankton called pseudo-Nitzschia. The bloom was present in Rhode Island and appeared to be creeping up the coast, prompting officials to close Nantucket Sound four days later.
Michael Hickey, shellfish program manager for the state division of marine fisheries, said Tuesday that samples taken last week did not show any toxins present. Results took a while to receive because shellfish had to be sent to labs in Florida and Maine; the tests are complicated, he said, beyond the ability of the state's shellfish lab.
“It's just a very complicated test, it's very expensive equipment,” he said. “Most state labs aren't set up to do that kind of work.”
Pseudo-Nitzschia can produce domoic acid, a biotoxin that accumulates in the guts of filter-feeding shellfish. Shellfish with high concentrations of the acid cause amnesic shellfish poisoning (ASP), the symptoms of which include vomiting, cramps, diarrhea and incapacitating headaches, followed by confusion, disorientation, permanent loss of short-term memory and in severe cases seizures and coma. No illnesses have been reported as a result of the phytoplankton bloom.
Hickey said the problem is that there are 13 species of pseudo-Nitzschia, seven of which produce toxins and four of which produce high levels of toxins. Isolating the species is what takes time.
He also said this particular strain can produce more toxins as it dissipates. “That's what we're trying to track,” he said.
Chatham Shellfish Constable Renee Gagne told selectmen Tuesday that while no toxins were present in the shellfish meats and waters that were tested, phytoplankton cells were found in high numbers in samples from Nantucket Sound, and in moderate numbers in Stage Harbor. Testing continued later in the week; she urged people to check the town's website for updates.
While there have phytoplankton blooms here in the past, Hickey said there has been “nothing at this scale” involving pseudo-Nitzschia. “It's pretty wide spread geographically. This is really the first time we've had to deal with this.”
The closure covers most species of shellfish, including clams and oysters. The closure does not include harvest of whelks, bay scallops or sea scallops for sale of the abductor muscle, which does not accumulate the toxin.
Chatham issues hundreds of commercial shellfish licenses and dozens of shellfishermen dig quahogs, steamers and mussels full time. Gagne said many of the areas impacted by the closure, including Oyster Pond, were already under seasonal closures, and with the Southway and east-facing areas still open, local shellfishermen have an alternative.
“Really one of the more productive areas is still open, which is the Southway,” she said.
Bassett urged consumers to ask to check the travel tag of shellfish they purchase or order in restaurants to ensure they are from open areas. “Our harvest areas are pristine and our product stands alone when it comes to cleanliness,” he said.
The widespread closure came just a few days before a different form of contamination was identified in Wellfleet oysters, prompting the closure of those beds just before last weekend's Wellfleet Oyster Festival. “We're dealing with two crises at once,” Hickey said, and are limited in the number of tests that can be run at state labs.
“We're doing the best we can as far as collecting samples and trying to get them run,” Hickey said.
Watch The Chronicle's website for updates on this story.