Climate change most likely suspect in Spofford Lake algae growth

Amanda McQuade, New Hampshire Department of Environmental Services' beach and cyanobacteria monitoring coordinator, collects a sample that looks like black sludge on the shore at B&K Aqua Club on Spofford Lake in September 2020.

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CHESTERFIELD, N.H. — Cyanobacteria has been sighted on Spofford Lake, prompting the state to issue another alert.

“Accumulations are appearing along shorelines as dark or black mats and fluffy material,” states the alert from the New Hampshire Department of Environmental Services. “This is similar to the material observed this July.”

However, said Darlene Smith, director of Chesterfield’s Parks and Recreation Department, the town’s two public beaches, Ware’s Grove and North Shore, are both open and safe for swimming.

And Kate Hastings, the state’s cyanobacteria harmful algal bloom program manager, said as long as swimmers don’t come into contact with the mats, they should be OK.

The alert doesn’t specify exactly where the blooms were discovered, but Smith said it appeared they were found in the same location, along the corner of the lake at Route 63 and North Shore Road.

“The mats of cyanobacteria have come from the bottom of the lake and are washing along the shores, carried by winds and currents,” states the alert. “This material can cause rashes and NHDES advises that lake goers avoid contact with these mats/accumulations of cyanobacteria. It is also important to keep pets from interacting with this material.”

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Folks who spot what appears to be cyanobacteria on the surface of a lake are urged to contact the DES at

“Surface blooms can rapidly change and accumulate in various locations around a waterbody,” states the alert. “Please continue to monitor your individual shorelines for changing conditions.”

Cyanobacteria are natural components of water bodies worldwide, though blooms and surface scums may form when excess nutrients are available to the water. Some cyanobacteria produce toxins that are stored within the cells and released upon cell death. Toxins can cause both acute and chronic health effects that range in severity. Acute health effects include irritation of skin and mucous membranes, tingling, numbness, nausea, vomiting, seizures and diarrhea. Chronic effects may include liver and central nervous system damage.

“Be cautious of lake water that has a surface scum, changes colors, or appears to have green streaks or blue-green flecks aggregating along the shore,” states the alert.

Visit the NHDES Harmful Algal and Cyanobacteria Bloom Program website for photos and more information about cyanobacteria at

Bob Audette can be contacted at