The likelihood of a red tide outbreak in the Gulf of Maine this spring and summer is "moderately large," researchers at the Woods Hole Oceanographic Institution (WHOI) and North Carolina State University (NCSU) advised yesterday.
Red tide is caused by naturally occurring algal blooms that produce a toxin ingested by feeding shellfish. While harmless to bivalves like clams, mussels and oysters, high levels of red tide toxins can cause people who eat them to become sick or even die.
Periodic red tide outbreaks have forced the closure of some New England shellfish beds to harvesting in recent years, causing a lapse in the region's clam, mussel and oyster supply.
Wednesday's advisory is based in part on a seafloor survey of quantities of Alexandrium fundyense, the algae that produces the toxin. The researchers found concentrations of Alexandrium cysts - the dormant seed-like stage of the algae's life cycle - in the Gulf of Maine to be 40 percent lower than the historically high levels observed prior to last year's bloom. But the concentrations are higher than the levels preceding a major regional bloom that closed shellfish beds from the Canadian border to Massachusetts Bay in the spring of 2006.
"Last year at this time, we issued an advisory for a very large regional bloom that did in fact occur. In hindsight, that advisory was ‘easy' because the cyst concentrations were higher than we had ever seen - 30 percent higher than in 2004 just before the massive 2005 red tide that many people probably remember," said Don Anderson, a senior scientist at the WHOI. "It's more difficult to make a prediction this year because the numbers of cysts we found are not extreme."
April 22, 2009
