Red menace

What's the Fourth of July without fireworks, sweet corn, something hot off the grill, and-if you live in New England-a clambake by the sea?

New Englanders need a backup plan for their quintessential rite as the height of summer draws nigh. Shellfish beds from Maine to Massachusetts-representing over a third of the nation's clam harvest-are closed due to one of the worst outbreaks in years of red tide, an algae bloom that is toxic to humans and absorbed by some shellfish.

The unusually heavy algae outbreak closed clam flats in northern Massachusetts starting in May, and many shellfish workers expect beds to be closed until September. While many fishermen remember the last severe red tide outbreak 12 years ago, or another historic influx in 1972, oceanographers say it has never traveled so far south or stayed so long. Shellfish beds in Nantucket Sound off Martha's Vineyard and Nantucket have never been closed before. Massachusetts Gov. Mitt Romney declared an emergency last month, allowing shellfish farmers-who say they are losing as much as $600,000 a week-to seek federal disaster aid.

Red tide, or Alexandrium fundyense, thrives in fresh water that washes into the ocean. Normally its natural enemy is zooplankton, but-in a process biologists say is like chemical warfare-the algae fights off the plankton by releasing its own toxins. Heavy rains this spring over the Atlantic are blamed for launching this cycle of vengeance.

Shellfish including clams, mussels, oysters, and some scallops retain the algae's toxin. (The fish aren't harmed, yet the toxin can be deadly to humans or wildlife if eaten.) Lobsters, crabs, shrimp, and finfish are safe, according to the Massachusetts Department of Public Health.

Health officials-and tourism operators-are worried about half-baked publicity. Northeastern restaurants serving the beloved fried clam are importing their bivalves from Canada or Maryland, yet visitors may wonder. Red tide infested waters are safe for swimming, but tourists may decide that affected waters-and canceled clambakes-are reasons to stay away.

Shellfish harvesters, meanwhile, are no fair-weather farmers. "No one made me go into this profession. I knew it would be feast or famine," 49-year-old John Grundstrom, a fourth-generation clammer, told The Boston Globe. He's seen red tide before, and bad weather, and predators, and other plagues on what is at best a cyclical profession. He's painting houses until the clam beds open again.