Red tide shuts bay to shellfishing

A potent red tide outbreak in Massachusetts Bay is worsening, according to scientists who have recorded some of the highest concentrations of the toxic algal bloom in three decades drifting in coastal waters. Massachusetts officials yesterday shut down shellfishing throughout Cape Cod Bay.

The bloom, made up of vast numbers of single-celled organisms, stretches from Northern Maine to Cape Cod Bay. While swimming is safe in the sometimes rust-colored water, algae's neurotoxins, which concentrate in shellfish meat, can cause illness or even death if consumed in enough quantity.

In recent weeks, state officials throughout New England have closed off dozens of shellfish beds, threatening the region's multimillion dollar shellfish industry, which sells clams, scallops, and oysters throughout the world. Only filter-feeder shellfish are affected, meaning that other sea creatures, including lobsters, crabs, and shrimp, are not.

In years when the red tide blooms in the Northeast, it normally starts off the coast of Maine and rarely extends as far south as the Cape. Scientists believe it has not occurred with the intensity researchers are seeing in Massachusetts Bay since 1972. In a normal year, scientists might find fewer than 100 of the organisms per liter; in the last week they recorded levels as high as 6,000 per liter.

''The levels of toxin are still rising and showing up in more places," said J. Michael Hickey, Massachusetts's chief shellfish biologist. He said toxic levels in the shellfish meat are increasing. ''This thing has not topped off yet."

Scientists suspect the unseasonably windy and wet weather in the last few weeks is exacerbating the outbreak.

The spring blooms are usually pushed offshore and away from coastal shellfish beds by westerly winds. But a persistent high-pressure weather system off Greenland has pushed bad weather, winds, and red tide back toward the coast with northeasterly winds. Heavy rains and abundant snowfall this year have also poured fresh water into coastal waters, creating perfect conditions for red tide to flourish.

Scientists are unsure how long the bloom will last, but say it could linger for as long as six weeks based on previous outbreaks. Even once the bloom dissipates, it takes weeks for shellfish to flush enough of the poison out of their system to be safe to eat.

''It's a terrible time for it to happen. This is the beginning of the season," said George Shamma, a Duxbury oyster farmer.

This should be prime harvesting time. But fishermen are grounded, and heavy rains and high winds have also prevented them from doing repair work on their boats.

''In the long run, we'll survive. But economically it's a difficult time for us," said Shamma. ''We're going without paychecks."

Deaths from red tide shellfish poisoning have occurred throughout the country, but locally caught or grown shellfish have never been known to kill anyone, although people have become sick, scientists said. Shellfish contaminated with the red tide toxin can cause a poisoning syndrome called paralytic shellfish poisoning. Symptoms are often numbness, tingling, wooziness, nausea, and difficulty breathing.

Currently, the worst outbreak is off the coast of Sandwich, and high concentrations have been detected all along the South Shore because, scientists believe, the prevailing winds in recent weeks have been pushing the blooms south. In addition to Cape Cod Bay, shellfish beds in the northern portion of Buzzards Bay in Bourne and Wareham were also closed yesterday.

As red tide cell count numbers grew last week, Massachusetts officials moved swiftly to close down beds, even those that did not show high levels of the poisoning. Hickey says it is safe to eat shellfish in stores and restaurants because it was caught before it could have been contaminated.

''The whole plan is to close these places before they get into commerce," says Hickey. ''My job first and foremost is public health."

Scientists have long been baffled by New England's red tide species, Alexandrium fundyense, one of dozens of red tide species that can bloom out of control across the world each year. The New England species spends most of its life in a dormant state as cysts carpeting the sea floor, says Don Anderson, a red tide specialist at Woods Hole Oceanographic Institution who is co-heading a five-year project studying harmful algal blooms at the Woods Hole Center for Oceans and Human Health.

Every February or March, an internal clock sends the cysts swimming to the surface. Then, depending on conditions such as nutrients, sunlight, and water temperature, the cells can divide and spread exponentially until there are thousands of cells per liter of seawater.

''In terms of cell abundance, this is probably the biggest outbreak in Massachusetts Bay since 1972," said Anderson. For reasons scientists don't fully understand, the cells often stop dividing in the summer months, fuse together, and drop to the sea floor as cysts again until they awaken the following year.

Most red tide outbreaks in Massachusetts Bay are blown here from offshore. But Anderson worries if this outbreak is severe enough, it will send enough cysts to the floor of Massachusetts Bay to make the bay a breeding ground for future red tide outbreaks, a dangerous phenomenon for the region's shellfishermen.

''[This organism] is always fooling us," said Anderson. His team, on its first cruise of the five-year project, helped confirm the outbreak that Hickey and other state shellfish biologists had suspected. Anderson's team and other scientists will monitor the red tide outbreak starting this weekend with emergency funding from the National Ocean Service.

In Maine, news of the red tide was greeted with groans. Fishermen said they have had a rough season because of the long winter, bad spring weather, and several flooding-related closures.

''It's kind of a double whammy because we've been hit with so many things already," said Chad Coffin, a clam digger from Freeport and the chairman of the shellfish committee. ''Now it looks like we're going to lose half of May and most of June."

If there's a silver lining, he said, hauls will probably be huge when fishermen are allowed back on the water. ''You could recoup some of the losses eventually," he said. ''But the more time you lose, the more difficult it is to catch up."

Beth Daley can be reached by email at bdaley@globe.com.