(Correction: Because of a reporting error in a story about red tide that ran on Page 1 on Sunday, the baseline value for toxins in shellfish meat was incorrect on second reference. On Boston's North Shore, isolated counts were over 2,000 micrograms per 100 grams of meat.)
The massive red tide festering off the coast of New England has spread to federal waters, closing thousands of square miles to shellfishing by Massachusetts boats as levels of the algae bloom's toxin hit all-time highs in the region's clams and mussels.
''Cumulatively, it is the worst outbreak ever," said J. Michael Hickey, the chief shellfish biologist for the state Division of Marine Fisheries. The agency ordered the federal waters closed to state shellfishermen late Friday and asked federal officials to extend the ban to out-of-state boats. The last red tide outbreak of a similar scope occurred in 1972.
Shellfish bed closures have already idled close to 2,000 clammers, oyster farmers, and mussel harvesters in state waters that stretch 3 miles from shore. The new ban extends that closure to more than 100 miles from shore. Officials expect fewer fishermen will be affected by the federal ban, although the new closure may hurt a robust fishery for ocean quahogs and surf clams. Niche fisheries in federal waters could also be affected.
The news arrives as New England officials scramble to cope with the devastating algae bloom that stretches from central Maine to Nantucket Sound. The Cape Cod Chamber of Commerce launched a public outreach campaign this weekend to educate tourists about the bloom. One of the world's authorities on red tide, Don Anderson of Woods Hole Oceanographic Institution, flew home early from a scientific conference in Barcelona yesterday to prepare for a red tide briefing on Tuesday with the New England congressional delegation in Washington, D.C.
The New England shellfishing industry is losing an estimated $3 million per week because of the red tide, and state officials say that if the outbreak lasts for the predicted eight to 10 weeks, the total impact could be close to $28 million.
The only good news in recent days, officials say, is that the outbreak has not progressed further south in coastal waters toward Rhode Island.
Massachusetts officials have authority to close federal waters only to fishermen with Massachusetts fishing licenses, Hickey said. He has put in a request with the US Food and Drug Administration to ask the National Oceanic and Atmospheric Administration to shut the area down to all fishermen. A spokeswoman for NOAA fisheries yesterday said she was unable to confirm the request.
Yesterday, shellfishermen in Massachusetts and Maine were awaiting word on whether they would be eligible to get low-interest loans and other disaster aid that governors Mitt Romney and John Baldacci applied for last week after declaring states of emergency because of the bloom.
The red tide, which has yet to take on its signature red-brown color, is made up of vast numbers of single-celled organisms that began an exponential growth explosion offshore last month. While swimming is safe, the algae's toxins, which concentrate over time in shellfish meat, can cause illness or even death if consumed in enough quantity. It does not affect lobsters, crabs, shrimp, or finned fish. The part of the scallop people eat in New England -- the adductor muscle -- does not retain the toxin and is safe to eat.
No one has become ill from the red tide, state officials said yesterday. However, Anderson said there have been reports of several dead terns at Monomoy National Wildlife Refuge and ducks in Audubon's Wellfleet Bay Wildlife Sanctuary, although analysis is needed to see if they died from eating contaminated shellfish.
All shellfish being served in restaurants and stores is safe to eat after having undergone rigorous testing, officials stressed yesterday. Many restaurants are buying clams from out of state, and customers can expect higher prices as a result. Still, despite the repeated reports about the red tide outbreak, tourists seemed to be getting only some of the message.
''We are getting calls, not so much about eating but about swimming . . . which is safe," said Wendy Northcross, CEO of the Cape Cod Chamber of Commerce. ''It would be such a shame to change plans because of bad information."
Red tide is naturally found in New England waters -- it appears so regularly off the coast that the Georges Bank area is permanently closed to shellfishing. However, this year's stubborn storms, winter snow runoff, and recent hot sun has created perfect conditions for the algae to bloom furiously and be blown close to shore.
Hickey -- and researchers from the Woods Hole Center for Oceans and Human Health -- said cell counts in the water remain high, but it was the counts in the shellfish meat that were the most worrisome.
Normally, shellfish beds are closed if there are more than 80 micrograms of toxin per 100 grams of shellfish meat. On the North Shore, isolated counts were over 2,000 micrograms per 1,000 grams of meat, while in Chatham they were around 1,800.
The high counts and the bloom's persistence troubles longtime red tide researchers like Anderson because there is some research that shows the more severe and long a red tide outbreak is, the longer it can take for some shellfish to purge the toxins from their bodies. Another worry is that the algae -- which rests on the sea floor much of the time as dormant cysts -- may begin populating Massachusetts Bay in greater numbers, triggering outbreaks year after year.
''As much as we are all exhausted, it is very, very important to map this out and learn about its footprint," said Anderson.
New England elected officials, meanwhile, said yesterday that aid would be coming for the beleaguered shellfish industry. US Senator Olympia J. Snowe of Maine said, ''I am confident we can find a way to bring relief to the workers and businesses that have been devastated by this outbreak."
US Representative Barney Frank of Massachusetts said the outbreak response was a clear example of how federal government can help an entire industry.
''For those people who say we don't need the government, that it is a nuisance, we need disaster relief, we need the government to sort this out," he said.
Beth Daley can be reached by e-mail at Bdaley@globe.com