On Thursday, the New Hampshire Department of Environmental Services (NHDES) removed a cyanobacteria advisory for Halfmoon Pond that was issued Aug. 12 after a bloom had been spotted there Aug. 11.
While the bloom accumulation has dissipated, NHDES advises that lake-goers look out for green surface accumulations in the future and continue to monitor the shoreline for changing conditions.
This advisory was not based on a toxin evaluation and was intended as a precautionary measure for short-term exposure. Cyanobacteria are natural components of water bodies worldwide, though blooms and surface scums may form when excess nutrients are available to the water. According to NHDES, some cyanobacteria produce toxins that are stored within the cells and 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 may include liver and central nervous system damage.
People are advised to be cautious of lake water that has a surface scum, changes colors or appears to have green streaks or blue-green flecks aggregating along the shore.
If people notice anything resembling cyanobacteria, they should not wade in, swim or drink the water, keep all pets out of the water and contact NHDES immediately by calling 603-848-8094 or sending email to hab@des.nh.gov.