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For Immediate Release
November 6, 2020


Amanda McQuaid, Harmful Algal Blooms Coordinator
(603) 271-0698 |

State Warns Lake Users of Late Season Cyanobacteria Blooms in New Hampshire

Concord, NH – Cyanobacteria blooms have been observed along shorelines of a few lakes and ponds this week. NHDES advises lake users to avoid contact with the water in areas experiencing elevated levels of cyanobacteria. NHDES also advises the public to keep their pets out of any waters that have a cyanobacteria bloom. 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. Please continue to monitor shorelines for changing conditions and avoid contact.

Cyanobacteria are natural components of water bodies worldwide, though blooms and surface scums may form when excess nutrients are available in 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.

If you notice anything resembling cyanobacteria, please refrain from wading, swimming or drinking the water. Keep all pets out of the water and contact NHDES immediately. Please call NHDES to report a cyanobacteria bloom at (603) 848-8094 or email