BOSTON – The red tide of algae that choked the Massachusetts coast last year may not, as scientists had feared, come back year after year for a recurring summer encore.

The toxic algae blooms drop microscopic cysts on the ocean floor which act like seeds for future red tide outbreaks. Despite the intensity of last year’s bloom, the cysts are far less widespread than expected on the Southern New England sea floor, according to a study by the Woods Hole Oceanographic Institution on Cape Cod.

“The initial reaction is being surprised and pleased,” said Don Anderson, a senior scientist at Woods Hole. “We had feared that this was another giant step down the coast by this organism.”

Red tide remains an annual threat in Maine. The existing hotspots off Penobscot and Casco bays are still alarmingly active, Anderson said. While researchers found an average of 10 to 40 cysts per cubic centimeter of sediment off the Massachusetts coast, the Maine concentrations remained in the 1,000 to 6,000 range, Anderson said.

He cautioned that cysts are only one of a variety of factors needed for a crippling red tide, which also include weather patterns and ocean currents.

Those factors converged last year and hatched a nasty algae bloom that winds pushed from Maine down to Massachusetts. The outbreak shut shellfishing beds as far south as New Bedford and cost shellfisherman tens of millions of dollars in lost income.

“The news about the pods is fantastic,” said George Shamma, an Duxbury oyster farmer. “An annual red tide would destroy the industry. I just hope that the science is accurate.”

Researchers are not entirely sure why cyst levels were so low off Massachusetts. They speculate that plankton may have eaten the algae cells before cysts formed, that the seeds may have been naturally dispersed by winds and currents or that the cysts were unable to survive on Massachusetts’ sandy seabed.

Last year’s algae bloom was the worst in New England since 1972 as organisms grew at 40 to 100 times the normal rate. Anderson and his colleagues took a dozen trips during and after the outbreak to measure the red tide and gather samples.

The cysts, about the size of a pin point, germinate like a seed and can take from a few months to a decade to bloom. The team counted the number of cysts per cubic centimeters of sand and other sediment pulled from the ocean floor.

After the 1972 outbreak, New England entered a 10-year stretch of intensified red tides, a pattern Anderson expects to repeat itself. The region should continue to see a “level of sustained toxicity,” but blooms as severe as last year’s will remain a rarity, he said.

Like a meteorologist, Anderson cautioned that red tide forecasts are fluid and dependent on a complex series of factors.

“It’s still early,” he said. “I would guess in another couple of weeks we’ll see what is really going to happen this year.”