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New Hampshire Department of Environmental Services

Media Center

DATE: September 25, 2018
CONTACT: Amanda McQuaid (603) 271-0698 (O), 848-8094 (C)

State REMOVES Cyanobacteria Lake Warning for Jones Pond in New Durham, NH

Concord, NH – The New Hampshire Department of Environmental Services (NHDES) has REMOVED a cyanobacteria lake warning issued on 7/20/2018 for Jones Pond in New Durham. NHDES issues lake warnings for cyanobacteria when concentrations exceed 70,000 cells per milliliter of lake water. This waterbody has been carefully monitored by NHDES, UNH (University of New Hampshire) and local volunteers. Jones Pond, Marsh Pond and Downing Pond (New Durham) were collectively examined for research purposes through the University of New Hampshire. Local volunteers were able to observe and report daily cycles of the blooms surfacing throughout Jones Pond and Marsh Pond, while no cyanobacterial blooms were observed on Downing Pond. Samples have been collected nearly every week to observe the conditions of the waterbodies. Duplicate sampling efforts and weekly communication were conducted between NHDES, UNH and volunteers. A deep layer bloom in Jones Pond had been evident for the duration of the advisory, and appeared to surface during the morning hours. The bloom was primarily comprised of Oscillatoria, estimated to be nearly 3 million cells/ml from samples collected from 0-3 meters at the deep site of the pond (July 20). Samples were collected near the dam on July 23 and 24, revealing estimates of 2 to 3.25 million cells/ml of Oscillatoria at the surface. Globs were often observed near shorelines in the morning, containing visibly high concentrations of cyanobacteria throughout the lake. Estimates from the dense globs were roughly between 10 million and 100 million cells/ml (between July 26 and July 27). Jones Pond was sampled again August 3 and 6, where it was evident that the bloom was still highly concentrated. Jones Pond was sampled again on August 16 and 17, with no evidence of surface blooms of cyanobacteria. However, these observations changed by the hour with evidence that the heaviest surface blooms were appearing in the early morning. On August 17, the bloom was observed deeper in the lake (~ 7 million cells/ml at 3 meters), and the advisory remained at that time due to its cyclical nature to surface-bloom. Samples were collected again on August 24, August 27, and August 30. Samples were collected between 0-3 meters of lake water and cell concentrations varied, though remained elevated at around 100,000 cells/ml. Occasional sightings of surface accumulations continued into September, but appeared to be an early morning event. By September 6, the bloom in Jones Pond had dissipated. The monitoring effort by UNH and volunteers continues, with the most recent samples collected on September 21 from Jones Pond. Please continue to monitor your individual shorelines for changing conditions.

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 that can be 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.

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.

The warning went into effect on July 20, 2018, and was removed on September 25, 2018.

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.

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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