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Cape Cod Times Nauset shellfishing halted by red tide
April 20, 2000
By John Leaning
STAFF WRITER
ORLEANS - An unexpected outbreak of potentially toxic red tide has forced the state to close the entire Nauset estuary system to shellfishing.
The closure was announced yesterday afternoon by the Division of Marine Fisheries and will remain in effect at least until Tuesday, said Michael Hickey, the division's chief shellfish biologist.
The closure involves shellfish beds in Eastham and Orleans.
"This came out of left field," Hickey said yesterday, noting that the algae that produced the toxin normally show up later in the spring, when water and air temperatures are on the rise.
Red tide contains a naturally occurring toxin that can be dangerous to humans in high concentrations.
Hickey said the levels found in samples taken Tueseday showed 118 micrograms of the toxin per 100 grams of mussel meat.
State regulations require closures when toxin levels reach 80 micrograms.
But Hickey also said that the closure level is conservative, and even at 118, the toxin levels pose no threat to humans.
For that reason, he said, he is not ordering any recall of shellfish from the area.
"If I even thought there was a problem, we'd be doing a recall, but we're not even close," he said yesterday.
The closure only affects bivalves - mussels, clams, quahogs, oysters and scallops.
Lobsters, crbas and shrimp are not subject to the closure, he said.
Hickey said this is the first report of red tide he has heard of anywhere in New England this year.
Normally, red tide is picked up later in the spring as the algae that produce the toxin migrate with currents south from the Gulf of Maine.
Last yeaer, for example, hot spots of red tide were picked up in May in the estuary, and the system was closed down. By the end of the month the entire system was reopened.
The toxin, paralytic shellfish poisoning, or PSP, is produced by a planktonic, microscopic algae.
In large concentrations, when the algae bloom, it can turn water a reddish hue, hence the name "red tide."
The toxin was found in mussels taken from Roberts Cove on the Orleans side of the Nauset estuary, which includes Nauset Cove, Nauset Harbor and the Nauset Marsh.
Mussels are used as sentinel mollusks, Hickey said, because they take up the toxin more quickly, and get rid of it faster, than other mollusks.
If sampling done Monday shows no evidence of the toxin anywhere else in any other mollusks, Hickey said the Nauset system, except for Roberts Cove, could be reopened Tuesday.
Roberts Cove would remain closed until three series of samples show toxin levels below the 80 microgram trigger.
Hickey said he wanted to reopen areas as quickly as he could.
"I am aware of the economic pressure. I understand the other side, that this is affecting people's livelihood," he said.
While no one knows yet where the red tide came from, Hickey suspects the algae may have been in cysts buried in the mud.
"Something must have distrubed them, and they resuspended in the water column and got them blooming. I have no idea what that was" he said.