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New Hampshire Department of Environmental Services

Media Center
DATE: August 2, 2013
Sonya Carlson (603) 271-0698 or (603) 419-9229

State Removes Cyanobacteria Warning for Horseshoe Pond, Merrimack, NH

Concord, NH – The cyanobacteria cell concentration in Horseshoe Pond, Merrimack, NH, is below a level of public health concern. As a result, the New Hampshire Department of Environmental Services (DES) has removed the cyanobacteria lake warning issued on July 17, 2013. Please continue to monitor your individual shoreline for changing conditions and avoid areas of contamination.

Samples collected today, August 2, 2013, from the beaches and boat launch had minimal amounts of cyanobacteria. However, once a bloom has been seen in a lake, that lake is more likely to have future blooms. Please continue to monitor your individual shoreline for changing conditions and avoid any large amounts of bluish-green growth in the water.

DES routinely monitors public beaches and public waters of the state for cyanobacteria. Once a cyanobacteria warning has been issued, DES returns to affected waterbodies on a weekly basis until the cyanobacteria bloom is not evident. Cyanobacteria are natural components of water bodies worldwide, but blooms and surface scums may form when excess phosphorus is 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, nausea, vomiting, and diarrhea. Chronic effects include liver and central nervous system damage.

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