State Issues Cyanobacteria Advisory for Long Pond in Henniker, New Hampshire

Concord, NH - A cyanobacterial bloom has been observed on Long Pond in Henniker. Blue-green flakes are present and most concentrated in wind-ward locations of the pond. Samples collected on 7/16/20 contained Planktothrix (Oscillatoria) with cell concentrations of at least 110,000 cells/ml where water appears clear. Advisories are issued when cyanobacterial cell concentrations exceed 70,000 cells/ml. As a result, the New Hampshire Department of Environmental Services (NHDES) has issued a cyanobacteria advisory for those who use the waterbody for recreation. The advisory is not based on a toxin evaluation and is intended as a precautionary measure for short term exposure. Lake-goers should continue to be on the lookout for blooms and avoid contact.

Surface blooms can rapidly change and accumulate in various locations around a waterbody. Please continue to monitor your individual shorelines for changing conditions. NHDES advises lake users to avoid contact with the water in areas experiencing elevated cyanobacteria cell conditions, also known as a bloom. NHDES also advises pet owners to keep their pets out of any waters that have a cyanobacteria bloom.

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.

The cyanobacteria advisory went into effect on July 16, 2020 and will remain in effect until NHDES confirms that cell concentrations of the bloom have subsided.