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New Hampshire Department of Environmental Services

Media Center

DATE: August 22, 2018
CONTACT: Amanda McQuaid (603) 271-0698 (O), 848-8094 (C)

State REMOVES Cyanobacteria Lake Warning for Sebbins Pond in Bedford, NH

Concord, NH – The New Hampshire Department of Environmental Services (DES) has REMOVED a cyanobacteria lake warning issued on 7/20/2018. Based on visual evidence, the cyanobacteria bloom was accumulating in coves throughout the pond appearing as dark blue-green globs. A sample collected July 19, 2018 was identified and enumerated. An estimate of over 30 million cells/ml of seven different types of cyanobacteria were found, comprised of Oscillatoria, Lyngbya, Merismopedia, Microcystis, Anabaena/Dolichospermum, Woronichinia and Aphanocapsa. Follow-up samples were collected from the shorelines on 7/26/2018 and a sample from Sebbins Pond Road had > 100,000 cells/ml of Microcystis. Samples were collected again on 8/7/2018 and contained 941,000 cells/ml of Microcystis, Anabaena/Dolichospermum, Woronichinia. Finally, samples were again collected on 8/20 and 8/21 from various side of the pond. The water was generally clear, though few globs of green were found accumulating at the surface near vegetation. Water samples showed very few colonies with an estimate of 1,000 cells/ml. Please continue to monitor your individual shoreline 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 August 22, 2018.

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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