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New Hampshire Department of Environmental Services

Media Center

DATE: September 21, 2018
CONTACT: Amanda McQuaid (603) 271-0698 (O), 848-8094 (C)

State REMOVES Cyanobacteria Warning for Winter Harbor on Lake Winnipesaukee in Wolfeboro, NH

Concord, NH – The New Hampshire Department of Environmental Services (DES) has REMOVED a cyanobacteria warning for the Winter Harbor area of Lake Winnipesaukee. The warning went into effect on August 30, 2018, and was removed on September 21, 2018.

Lake volunteers were tracking the Gloeotrichia bloom daily by visual observations. Samples were also collected for analyses using CyanoScope, a monitoring approach set out by the Environmental Protection Agency ( The bloom was not observed on Carry Beach, though was accumulating in various private coves in the area. Samples were collected August 29, September 5, September 6 and September 13. Several reports by lake residents from various towns across Lake Winnipesaukee were also submitted. Samples were not collected from other areas of Lake Winnipesaukee as low concentrations were observed and reported. The most significant concentrations were reported from Winter Harbor on September 5, 2018. NHDES analyzed these samples for the identification and enumeration of the bloom. Concentrations of Gloeotrichia exceeded 70,000 cells per milliliter from samples collected along coves and shorelines of Winter Harbor. Since that time, daily observations have been made that the bloom has slowly dissipated from the area. Please continue to monitor your individual shorelines for changing conditions.

Gloeotrichia – Large, deep NH lakes (such as Lake Winnipesaukee and Lake Sunapee) have been found to contain a unique cyanobacteria bloom called Gloeotrichia. Each colony of Gloeotrichia may contain approximately 5,000 cells. The colonies look like very small, fuzzy balls in the water. They can appear either green or sometimes brownish-yellow by eye. Often these cyanobacteria do not accumulate to large concentrations and may go unnoticed.  These types of cyanobacteria do not typically form green surface scums, however they can quickly accumulate along shorelines and coves. Various NH researchers are studying the Gloeotrichia cyanobacteria to learn more about these unique blooms.

To learn more, follow the links:

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, blue-green flecks, or even clouds of tiny balls like these. Changes in water color or clarity, though typically aggregating along the shore, may also be signs of cyanobacteria growth. NHDES advises pet owners to keep their pets out of any waters that have a cyanobacteria bloom in order to avoid consumption of cyanobacterial-contaminated lake water.

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 aims to return to affected waterbodies on a weekly basis until the cyanobacteria standards are again met.

loeotrichia under compound light microscopy at 100x.<
Gloeotrichia under compound light microscopy at 100x.

Gloeotrichia collected from a cove along Winter Harbor on August 29, 2018.
Gloeotrichia collected from a cove along Winter Harbor on August 29, 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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