PORTLAND — Maine and the rest of New England have had a second straight year of mild red tide outbreaks, bringing a sigh of relief to the clamming industry following two consecutive years of widespread clam flat closures because of red tide.

Clam diggers were hurt in 2008 and 2009 when red tide outbreaks resulted in extended closures of hundreds of miles of clam flats in Maine.

But only small numbers of clam flats have been shut down this summer because of red tide, said Darcie Couture of the Department of Marine Resources. The flats that were closed were shut down for relatively short periods, and the toxin levels of the red tide blooms didn’t reach unusually high levels as seen in past years.

“I always expect the worst and heave a sigh of relief when it doesn’t happen. I think we’ve dodged the bullet,” said Jim Markos, general manager of Maine Shellfish Co. in Ellsworth.

Clam and mussel harvesters have also been helped by the dry weather, with few flats being shut down because of bacterial pollution caused by runoff from rainstorms.

“The timing of this has been nice considering the economy,” said Couture, who is director of the DMR’s biotoxin monitoring program. “The clam diggers didn’t suffer a double whammy of a natural disaster on top of everything else.”

Red tide is caused by naturally occurring algae that produce a toxin shellfish absorb as they feed. Red tide taints clams and mussels, making them unsafe for people to eat, but poses no risk to those who eat fish, lobster, scallops and shrimp.

Officials close clam flats when toxicity levels get too high. When large numbers of flats are closed for prolonged periods, it can lead to clam shortages and drive up prices for steamers and fried clams.

Scientists this year predicted a moderate red tide season, said Don Anderson, a senior scientist at Woods Hole Oceanographic Institution in Falmouth, Mass., who heads the Gulf of Maine Toxicity Research Program.

While there were red tide closures at one time or another along much of the Maine, New Hampshire and Massachusetts coasts, the toxicity levels never reached the elevated levels found in 2008 and 2009, Anderson said. In 2009, for instance, toxin levels were as much as 50 times above the threshold at which harvest areas must be closed.

It’s hard to predict how severe or mild red tide will be each year. In 2010, scientists warned of extensive outbreaks and urged clam harvesters to prepare for the worst. But the predictions didn’t pan out, with only a few scattered, short-lived clam flat closures.

Scientists can’t forecast next year’s red tide based on what’s happening this year, he said.

“Just because we’ve had a year or two that are low in closures, it doesn’t mean we might not have a big one coming up next year,” he said.

But scientists hope to get a better handle on red tide with a new instrument that was deployed in the waters off New Hampshire last spring. The device, which was placed about 60 feet deep and was connected to a buoy on the surface, filters the ocean water and counts and analyzes red tide cells, sending the information to scientists’ computers in their laboratories.

Anderson said he expects more of the devices to be deployed throughout the Gulf of Maine in the coming years to provide real-time data about red tide.

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