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New Hampshire Department of Environmental Services

Media Center

DATE: July 3, 2018
CONTACT: Amanda McQuaid (603) 271-0698 (O), 848-8094 (C)

State Issues Cyanobacteria Lake Warning for Post Pond in Lyme, New Hampshire

Concord, NH – A cyanobacteria bloom has been accumulating in Post Pond of Lyme, New Hampshire. Based on visual evidence on June 29, 2018, the cyanobacteria bloom was accumulating at Chase Beach. The bloom appeared white, indicating cell death. Cyanotoxins may be released upon bloom decay. On July 3, 2018 the Chase Beach was clear and no cyanobacteria were found. However more bloom accumulations were found along Post Pond Lane. It is typical for blooms to accumulate in other areas or shorelines as wind and currents move them around. Samples collected July 3, 2018 contained Anabaena/Dolichospermum and Woronichinia at concentrations greater than 70,000 cells/ml. As a result, the New Hampshire Department of Environmental Services (NHDES) has issued a cyanobacteria lake warning for those who use the waterbody for recreation. The beach advisory has been removed at this time. It is advised to look out for accumulations in other areas of the lake or shorelines. Please continue to monitor your individual shoreline for changing conditions.

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 typically where lake water has a surface scum, green streaks or blue-green flecks aggregating along the shore. NHDES also advises pet owners to keep their pets out of any waters that have a cyanobacteria bloom.

NHDES routinely monitors public beaches and public waters of the state for cyanobacteria. Once a cyanobacteria lake warning or beach advisory 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 nutrients are 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, tingling, numbness, nausea, vomiting, seizures and diarrhea. Chronic effects include liver and central nervous system damage.

The warning went into effect on June 29, 2018, and again on July 3, 2018 as it was modified to a lake warning. The warning will remain in effect until additional samples reveal cyanobacteria levels have diminished.

Visit the NHDES Beach Program website for photos and more information about cyanobacteria at
Updates on advisories and warnings may be obtained at
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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.

NH Department of Environmental Services | 29 Hazen Drive | PO Box 95 | Concord, NH 03302-0095
(603) 271-3503 | TDD Access: Relay NH 1-800-735-2964 | Hours: M-F, 8am-4pm

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