MEREDITH — The New Hampshire Department of Environmental Services has issued a lake warning about a cyanobacteria bloom in Lake Wicwas, saying that samples collected on Aug. 7 contained 119,000 cells per milliliter of Anabaena/Dolichospermum and Microcystis.
New Hampshire uses a threshold of 70,000 cells per milliliter of lake water as a guideline for posting advisories or lake warnings for recreational exposure to cyanobacteria.
The cyanobacteria lake warning advises people to look out for accumulations in other areas of the lake or shorelines.
Officials said the warning is not based on a toxin evaluation; rather, it is intended as a precautionary measure for short-term exposure. Lake users should 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.
Officials also advise pet owners to keep their pets out of any waters that have a cyanobacteria bloom.
Once the department issues a cyanobacteria lake warning or beach advisory, it returns to affected water bodies on a weekly basis until the cyanobacteria count returns to normal.
Cyanobacteria are natural components of water bodies worldwide, but blooms and surface scum may form when excess nutrients are available to the water. Some cyanobacteria produce toxins that are stored within the cells until they are 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 Aug. 9 and will remain in effect until additional samples reveal cyanobacteria levels have diminished.