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May 01, 2008 02:44 pm
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Photos
Courtesy photo
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Red tide rising: Scientists find 30 percent more spores than in 2005 crisis
The algae are gathered in the flesh of filter-feeding bivalves — soft-shelled clams and their immediate cousins, but not lobsters, crabs or scallops — in concentrations that render the healthy shellfish toxic to humans, and can induce paralytic shellfish poisoning.
By Richard Gaines
CNHI News Service
GLOUCESTER, Mass. — As the sea warms up at this time each year, the seeds of a plant buried just offshore in the sediment of the Gulf of Maine germinate into cells that swim to the surface — and there are more of those seeds this year than scientists have ever seen before.
Typically, the algae — known to science as Alexandrium fundense — concentrate into blooms so dense they turn the surface of the ocean crimson.
If conditions are just so, these blooms of red tide will be pushed in-shore by northeast winds and carried south by the prevailing currents, and it is here in the protected, shallow waters of Maine, New Hampshire and Massachusetts that the red tide wreaks its havoc on coastal economies committed to shellfishing since Native Americans were digging by themselves.
The algae are gathered in the flesh of the filter-feeding bivalves — soft-shelled clams and their immediate cousins, but not lobsters, crabs or scallops — in concentrations that render the healthy shellfish toxic to humans, and can induce paralytic shellfish poisoning.
Traditionally, even before concentrations rise to dangerous levels, the harvesting and sale of affected shellfish are halted. In 2005, the bloom and distribution of the toxin were pandemic along the northern New England coast, and shellfishermen, their buyers, distributors and restaurants from the Bay of Fundy to Martha's Vineyard suffered losses estimated at more than $50 million.
It was the greatest red tide since 1972. So extensive were the losses that the Woods Hole Oceanographic Institution was granted $540,000 by the federal government to survey the floor of the Gulf of Maine for the distribution of the cysts or seeds that settle to the bottom each fall and produce modeling for future outbreaks. What the team from Woods Hole found last fall in the Gulf of Maine — now coming back to life — are more seeds by far than were transformed into the great red tide bloom of three years ago.
"It's watch and wait time," Don Anderson, the senior scientist, director of the Coastal Ocean Institute and recognized red tide expert, told the Times Wednesday.
The regional observation and modeling program known as the Gulf of Maine Toxicity study organized from Woods Hole has found a worrisome concentration of the red tide algae seed. The seafood study by Anderson's team found "the number of cysts is more than 30 percent higher than what was observed in the sediments prior to the historic (2005) bloom," the institution reports. Already, there have been isolated closures in Cape Cod and Maine.
Anderson explained that the super size of the seed bed was not by itself certain to produce widespread red tide harvesting closures later this spring. But the other natural conditions are in place. These include the necessity of unusual amounts of snowfall and winter rain. The coast received record amounts of both.
What else is required to bring red tide to civilization? Winds. Northeast winds, a fairly typical pattern for spring, will push the blooms into estuaries such as those along the coast of Essex County. Southwest winds, which are not atypical, can keep huge blooms out at sea, where they can remain for months, harmless to coastal economies.
"Our hypothesis is that cyst abundance is an indicator of the magnitude of the bloom," said Woods Hole oceanographer Dennis McGillicuddy in a report on the institute's Web site. He and his team were at sea this week on the research vessel Oceanus.
"If there is a large bloom offshore," he wrote, "the wind patterns and ocean currents in the next few weeks will determine whether it will be transported onshore and have an effect on coastal shellfish resources."
Richard Gaines can be reached at rgaines@gloucestertimes.com
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