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New Hampshire Department of Environmental Services

Media Center

DATE: August 29, 2018
CONTACT: Amanda McQuaid (603) 271-0698 (O), 848-8094 (C)

State Issues Cyanobacteria Lake Warning for Lake Winona in New Hampton and Center Harbor, New Hampshire

Concord, NH – A cyanobacteria bloom has been observed in Lake Winona in New Hampton and Center Harbor, New Hampshire. Samples collected August 28 and 29, 2018 contained roughly 100,000 to over 1 million cells/ml of Anabaena/Dolichospermum. New Hampshire uses a threshold of 70,000 cells per milliliter of lake water as a guideline for posting advisories or lake warnings for recreational exposure to cyanobacteria. The bloom was accumulating along shorelines and seemed to be isolated, but quickly grew over the last few days. The bloom can be elusive and disperse or accumulate along other shorelines. Volunteers helped survey the lake and found few accumulations around the lake. The worst part of the bloom was estimated to have cell concentrations in the millions per milliliter. 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. It is advised to look out for accumulations in other areas of the lake, coves or shorelines. Please continue to monitor your individual shorelines 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 August 29, 2018, and 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.

Cyanobacteria on Lake Winona in New Hampton and Center Harbor  

Cyanobacteria bloom accumulations along shorelines of Lake Winona on August 28, 2018.

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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