Red tide has spread from central Maine to Gloucester, making it unsafe to harvest soft-shell clams or mussels from those coastal waters and potentially signaling the onset of a business-damaging season, state officials say.
The single-celled algae carries toxins that concentrate over time in shellfish, making them poisonous, even lethal. Red tide often occurs in late spring and summer, when the algae grow rapidly. Crabs, lobsters, fish, and shrimp are not affected.
A combination of abundant beds of the algae seeds and excess winter precipitation could translate into the worst red tide season since 2005, oceanographers at the Woods Hole Oceanographic Institution say.
The 2005 outbreak, which also began in the middle of May, extended from northern Maine to Nantucket with algae counts 40 to 100 times higher than normal. It halted business for nearly 2,000 clammers, oyster farmers, and mussel harvesters for much of the summer. They lost tens of millions of dollars.
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http://www.boston.com/news/local/articles/2008/05/17/red_tide_has_spread_from_maine_to_mass/