State Issues Cyanobacteria Warning for Keyser Pond in Henniker

Concord, NH – An elevated cyanobacteria cell concentration has been measured in Keyser Pond, Henniker.  Samples revealed that the state threshold of 70,000 cells/ml or greater of cyanobacteria was exceeded.  The cyanobacteria were identified as Anabaena (Dolichospermum).  As a result, the New Hampshire Department of Environmental Services (NHDES) has issued a cyanobacteria warning for those who recreate on Keyser Pond.  The current bloom is appearing as dark, green and brown water throughout the water column.

This warning is not based on a toxin evaluation and is intended as a precautionary measure for short term exposure. NHDES advises lake users to avoid contact with the water in areas experiencing elevated cyanobacteria cell conditions. NHDES also advises to keep pets and small children out of any waters that have green turbid water, surface scums or blue-green or bright green flecks in the water column.

NHDES routinely monitors public beaches and public waters of the state for cyanobacteria. Once a cyanobacteria warning has been issued, NHDES returns to affected waterbodies on a weekly basis until the cyanobacteria standards are again met. Cyanobacteria are natural components of water bodies worldwide, but blooms and surface scums may form when excess phosphorus is available to the water.  Some cyanobacteria produce toxins that are stored within the cells but 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, nausea, vomiting, and diarrhea. Chronic effects include liver and central nervous system damage.

The warning went into effect on July 25, 2017, and will remain in effect until additional samples reveal cyanobacteria levels have diminished.

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