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New Hampshire Department of Environmental Services

Media Center

DATE: October 12, 2018
CONTACT: Amanda McQuaid (603) 271-0698 (O), 848-8094 (C)

State Issues Cyanobacteria Lake Warning for White Oak Pond and Pipers Cove of Squam Lake in Holderness, New Hampshire

Concord, NH – A cyanobacteria bloom has been observed on White Oak Pond in Holderness, NH. The bloom appeared near the outlet connecting to Pipers Cove on Squam Lake. The bloom was also observed at the Squam Lake Association boat launch on Squam Lake in Holderness, New Hampshire. A sample was collected on October 9, 2018 from White Oak Pond. The Squam Lake boat launch was sampled on October 10, 2018. Both samples were identified and enumerated, appearing to have been a connected bloom between the two waterbodies. An estimate of 4.4 million cells/ml of cyanobacteria, comprised of Microcystis and Anabaena/Dolichospermum, were found on White Oak near the outlet. The Squam Lake boat launch near the inlet had 1.75 million cells/ml of the same types of cyanobacteria. The state threshold for a warning or advisory is 70,000 cells/ml of cyanobacteria in NH lake water. There have been no reports or sightings of the bloom since then. NHDES will sample again next week and will update as soon as possible. At this time, the New Hampshire Department of Environmental Services (NHDES) has issued a lake warning for those who use the waterbodies for recreation. It is advised to avoid contact, especially keeping pets and children away from blooms. 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 October 12, 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
Follow the Beaches twitter feed:

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.


comparison view of bloom
A side by side comparison of the bloom from the Squam Lake Association Boat Launch and White Oak Pond in Holderness, NH.

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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