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By DOUG FRASER STAFF WRITER Red tide closes Nauset estuary to shellfishing
May 1, 2001
EASTHAM - Those April showers bring May flowers. Unfortunately, they also bring algae blooms.
The state closed the Nauset estuary to the harvest of all shellfish on April 12 due to high concentrations of the Alexandrium algae, also known as red tide, the toxins of which can cause potentially fatal shellfish poisoning.
Mike Hickey, the state Division of Marine Fisheries chief shellfish biologist, believes the heavy rains and winds of an early April storm churned up cysts of the red tide algae that were resting on the bottom. Several post-storm days of warm sunshine energized the cysts, which were then floating closer to the surface, and the algae joined the crocuses and snow drops in spring's first bloom.
Orleans Harbor Master Dawson Farber said the closure affected between 12 and 15 Orleans shellfishermen and two aquaculture grants located in his town. Farber said shellfishermen switch to other open areas of the town, minimizing the impact of the closure. Aquaculturalists must wait, however, until the state reopens the area.
Eastham Harbor Master Henry Lind said between six and 10 shellfishermen were affected by the closures in his town along with a half-dozen aquaculture grants. Typically, the estuary is for red tide algae are closed for five weeks.
Red tide has been around for a long time. Lind said the Jamestown colony may have been wiped out by the shellfish poisoning. American Indians would send out coastal patrols to warn villages of the red tide.
The state closes an area when the toxin level in the shellfish meat approaches 80 micrograms per hundred grams of meat. It will not reopen an area until the concentration drops below 80 and declines for three days of sampling in a row. Hickey is hoping that sampling done yesterday and later this week will lead to the estuary being reopened by the end of the week or early next week.
Depending on the species, it takes from a couple of days to a couple of weeks for shellfish to purge the toxins from their systems. DMF biologists take samples from shellfish to predict an opening date. They also close areas well in advance of reaching toxic levels.
"The good news is that this is another assurance to the public that we're taking care of their health. The state takes a very conservative approach," said Lind.
Last year, red tide closed the estuary for over six weeks.
Nauset estuary is one of the few areas of the Cape that sees these early spring closures. That, said Hickey, is not due to a decline in water quality because of environmental factors, such as pollution by septic discharge and lawn and agricultural fertilizers.
Instead, he believes Nauset's annual spring red tide is due to survivors of a massive bloom that occurred in 1972. Biologists are pretty sure the seed beds for red tide algae are located in the Bay of Fundy. The algae blooms of spring and early fall spread from Casco, Maine, down to the Carolinas. That bloom was so big in 1972 that some algae made it over the bar at Nauset Inlet into the estuary.
The algae prefer a narrow temperature band that typically exists in spring and fall. As winter approaches, the algae make cysts that drop to the bottom and wait for more favorable conditions. If the temperature climbs sharply from cold to warm in the spring, or drops off sharply in the fall, the cysts will not open and will be buried by sedimentation, depleting the numbers that will bloom in the next season.