The state has removed it warning about a bacteria bloom at Elm Brook Park Beach in Hopkinton.
The New Hampshire Department of Environmental Services places the warning after water samples on June 12 found more than acceptable levels of cyanobacteria.
Follow-up testing on Wednsday, June 20, found that the levels had declined to zero and there were no visible signs of cyanobacteria, sometime incorrectly called blue-green algae.
This waterbody is monitored by the Army Corp of Engineers and observations were made at the boat launch, beach and fishing platform.
Cyanobacteria are natural components of water bodies worldwide, but blooms and surface scums can form when excess nutrients enter 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.
DES 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.
The NHDES Beach Program website has photos and more information about cyanobacteria: des.nh.gov/organization/divisions/water/wmb/beaches/index.htm
