State REMOVES Cyanobacteria Advisory for Halfmoon Lake in Alton and Barnstead, NH

Concord, NH – The New Hampshire Department of Environmental Services (DES) has REMOVED a cyanobacteria advisory for Halfmoon Lake that was issued on 8/20/2019. Most recent samples were collected on 8/22 and there were less than 1,000 cells/ml of cyanobacteria. The bloom quickly dissipated, however there have been a few reported sightings of the bloom since it was first issued. No new samples have been collected to prove that there are still surface blooms on the lake. Please continue to monitor your individual shoreline for changing conditions and report back if you see a surface bloom on the lake.

NHDES monitors public beaches and public waters of the state for cyanobacteria. Once a cyanobacteria advisory has been issued, NHDES returns to affected waterbodies weekly until the cyanobacteria standards are again met. NHDES advises lake users to avoid contact with the water in areas experiencing elevated cyanobacteria cell conditions. NHDES also advises pet owners to keep their pets out of any waters that have a cyanobacteria bloom.

This advisory was not based on a toxin evaluation and was intended as a precautionary measure for short term exposure. 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 advisory went into effect on August 20, 2019 and was removed on August 27, 2019.

Visit the NHDES Beach Program website for photos and more information about cyanobacteria at https://www.des.nh.gov/organization/divisions/water/wmb/beaches/index.htm

Updates on advisories and warnings may be obtained at http://www4.des.state.nh.us/WaterShed_BeachMaps/WaterShed_BeachMaps.aspx

Follow the Beaches twitter feed: https://twitter.com/NHDES_Beaches

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.