Officials Say Alum Unrelated To Pilgrim Lake Bloom

by Ryan Bray
Pilgrim Lake remains under a public health advisory due to a “potentially harmful algal bloom.” But members of the town’s marine and fresh water quality committee say the bloom is unrelated to a recent alum treatment in the lake. FILE PHOTO Pilgrim Lake remains under a public health advisory due to a “potentially harmful algal bloom.” But members of the town’s marine and fresh water quality committee say the bloom is unrelated to a recent alum treatment in the lake. FILE PHOTO

ORLEANS – Town officials and scientists say that recent cyanobacteria activity at Pilgrim Lake is not an indication that a spring alum treatment was ineffective.

Water quality testing continues at the lake, which has been under a public health advisory from the town’s health department due to a “potentially harmful algal bloom” since June 12. The lake is not closed to residents and visitors, but the health department in its advisory posted to the town’s website recommends against people and pets swimming there.

“It may be unsafe for people and pets, so please do not swim or play in the water at this time. If you come into contact with the water, rinse off,” the advisory reads.

Pilgrim Lake was subject to an extended closure through much of last August due to an algal bloom. The lake reopened to swimming on Sept. 7.

At a special town meeting in October, voters authorized spending $50,000 in free cash to treat the lake with aluminum sulfate, or alum. The treatment, which has also been employed at Uncle Harvey’s Pond and Crystal Lake, disrupts algal growth by binding to phosphorus in the deepest part of the waterway.

Town Manager Kim Newman said in an email that Pilgrim was treated with alum in early March. But members of the town's marine and fresh water quality committee last week said the recent bloom at Pilgrim is unrelated to the recent treatment.

“The actual alum treatment does sequester phosphorus that’s in the water column, but it doesn’t do anything to the phosphorus that’s already in the sediment and so forth,” said Richard Levy, the committee’s chair. “So these things can actually happen.”

Committee members conduct regular monitoring at the lake with the help and guidance of professionals including staff with the Association to Protect Cape Cod and the coastal systems program at UMass Dartmouth’s School for Marine Science and Technology. Ed Eichner, a water scientist and professor at the school, has worked with the committee to create management plans for select ponds and lakes in town.

“What we’re seeing now, or what has been seen, is not the result of the alum treatment or the failure of the alum treatment,” he said of the recent activity at Pilgrim. “It is a shallow water phenomenon. It is not a deep water phenomenon. It’s the result of something that is going on in the shallow waters.”

Judy Scanlon, a marine biologist and member of the marine and fresh water quality committee, said there are a number of factors that could have contributed to the most recent bloom, among them warmer temperatures, wind, sunlight and the lake’s wave activity.

But Scanlon said it can be easy for people to correlate the recent bloom with the spring alum treatment, especially as the effectiveness of alum has been publicly met with skepticism by some in the community.

“I guess my main concern is that people have expectations about the alum treatment, and when you have a small increase in cyanobacteria and activity in the phytoplankton community, people automatically assume that the alum’s not working,” she said. “And it’s not really related.”

Eichner said blooms are common this time of year in clearer waterways such as Pilgrim as sediments warm up. He also said that last summer’s bloom could be having a “residual effect” on the lake closer to shore.

Levy, meanwhile, suggested that a wet spring could have also played a part in the current conditions.

“We’ve had a very strange spring into summer here weatherwise,” he said. “We had a lot of rain.”

“Cyanobacteria is naturally occurring in all our lakes and ponds,” Scanlon added. “It’s there. So only when conditions favor its growth does it start to multiply more rapidly. There can be short bursts of nutrients that can cause it to start to multiply.”

Staff with SMAST work with towns all across Southeastern Massachusetts, Eichner said. In many of the waterways that staff have observed over the years, he said a trend of increased impairment has been observed.

“They’re losing their clarity,” he said. “Their nutrient levels are going up. Some of them are starting to see more blooms. All of this is a product of how phosphorus moves with the groundwater.”

One source of impairment is materials from developments as far back as the 1980s and 1990s, Eichner said, which only now are beginning to “arrive” and become evident in local waterways.

“A large number of the deeper ponds had impaired conditions deep within them for a very long time,” he said. “Those impairments are now starting to impact the shallower waters. We’re starting to actually see it.”

Levy and Scanlon said in their sampling and observations, they’ve noticed improvements in the lake’s water quality since the June 12 advisory.

“Right now, it looks like it’s actually cleared up by the herring run,” Levy said. “The flow out of Pilgrim goes to the herring run. We’ve seen stuff collect there. There was an awful lot of pollen and other materials in there, too. It gets to be a complex sampling challenge.”

However, the advisory remained in effect as of June 21. The town is awaiting two consecutive water samples from APCC that demonstrate toxicity levels low enough to drop the advisory. The health department said on the town website that it would have a status update on the lake on June 27.

Going forward, Levy said that the committee wants to prepare a cyanobacteria education program with the town’s health department to better educate the public about the committee’s findings on cyanobacteria.

“It will basically be presenting the science around cyanobacteria in fresh water environments, because they’re always present,” he said.

The Pilgrim Lake advisory came less than two weeks after a similar public health advisory was issued for Boland Pond on May 30. That advisory was lifted on June 20, according to Jamie Demas, who has been conducting sampling at the pond with the nonprofit Orleans Pond Coalition.

In an email to the committee June 19, Dr. Julie Hambrook Berkman, director of pond and cyanobacteria monitoring programs for APCC, declared the pond as “acceptable,” noting that there was no evidence of scum on the surface and that testing showed a “negative growth rate.”

Unlike Pilgrim Lake, Boland Pond does not have a management plan. But Scanlon said there could be efforts made to encourage the town to support the creation of such a plan for the pond in the future.

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