State Issues Cyanobacteria Advisory for Middle Danforth Pond (Danforth Ponds and Bay) in Freedom, New Hampshire

Concord, NH - A cyanobacteria bloom has been observed throughout Danforth Bay of Middle Danforth Pond in Freedom. The bloom was first reported on August 17, appearing as blue-green flecks throughout the water. Samples were first collected by Green Mountain Conservation Group (GMGC) who found an abundance of Oscillatoriales. Samples were collected by NHDES on 8/18 and lake water contained cyanobacteria (Oscillatoria) with concentrations ranging from 500,000 cells/ml in clear-looking water to 2.5 million cells/ml in proximity to where clumps are observed. The bundles or clumps themselves represent millions of cells. 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.

A cyanobacteria bloom has been observed throughout Danforth Bay of Middle Danforth Pond in Freedom. The bloom was first reported on August 17, appearing as blue-green flecks throughout the water. Samples were first collected by Green Mountain Conservation Group (GMGC) who found an abundance of Oscillatoriales. Samples were collected by NHDES on 8/18 and lake water contained cyanobacteria (Oscillatoria) with concentrations ranging from 500,000 cells/ml in clear-looking water to 2.5 million cells/ml in proximity to where clumps are observed. The bundles or clumps themselves represent millions of cells. 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.

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 August 18, 2020 and will remain in effect until NHDES confirms that cell concentrations of the bloom have subsided.