Red tide packs an early punch in Maine waters

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The early spring appearance of red tide in Maine shows possible danger signs this summer for the shellfish industry.

"We're actually seeing an early start," says Darcie Couture, director of the biotoxin monitoring program for the Maine Department of Marine Resources.

"Our first shellfish closure was on March 24, which is a full month earlier than last year - or in the last 30 years."

The closure means it is unlawful for anyone to dig, take or possess any mussels or carnivorous snails in the eastern area of Casco Bay, which includes the shores of Harpswell, Brunswick, West Bath and Phillipsburg.

Red tide is the name for a harmful bloom of single-celled Alexandrium fundyense algae that appears red or brown and adds a reddish color to the affected seawater. The blooms of the plankton cause paralytic shellfish poisoning. Red tide is a result of coastal environmental conditions that include warm surface temperatures, low salinity and calm seas, according to Couture.

"We have been having unusually warm weather this year," says Couture. "Northeast winds tend to blow everything in toward the shore and we've been getting a lot of those as well."

Couture says average peak times for the algae blooms are between the end of April to the end of September. When the weather cools down, the red tide organisms form hardened cysts that sink to the ocean floor and wake up when the weather becomes warmer in the spring.

"Our highest concentration in Maine last year was over 8,000 micrograms of red tide toxin found in mussels," says Couture. "To give an idea of the severity, we only need 80 micrograms to quarantine an area."

During an ocean floor survey conducted last fall, Woods Hole Oceanographic Institution in Woods Hole, Mass., found the abundance of cysts in the Gulf of Maine to be 60 percent higher than in 2005. Research also showed the cysts have expanded south toward New Hampshire and Massachusetts.

"We are supposed to be getting southwesterly winds, which will hopefully push some of this out into open water and away from shellfish beds," says Couture. "The good news is we have dealt with this before and research allows us to be prepared for it. The worst part of it is usually between June and July, but there is no telling at this point whether it will reach epic proportions."

This article originally appeared in the New England Home Waters Section of the June 2010 issue.