State Removes Cyanobacteria Advisory for Harvey Lake in Northwood, New Hampshire

The New Hampshire Department of Environmental Services (NHDES) has REMOVED a cyanobacteria advisory for Harvey Lake that was first issued on 8/9/21 (removed on 9/3/2021) and re-issued on 9/8/2021. Some surface accumulations were still observed on 10/21/21 and samples contained cyanobacteria concentrations of only 15,000 cells/ml; including Microcytsis, Dolichospermum and Woronichinia. While the bloom accumulation has dissipated, NHDES advises that lake-goers look out for green surface accumulations in the future. Please continue to monitor your individual 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.  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. 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.  

The re-issuance of this advisory went into effect on September 8, 2021 and was removed on October 25, 2021.

• Visit the NHDES Beach Program website for photos and more information about cyanobacteria.
• View updates on cyanobacteria advisories.
• Follow the Beaches twitter feed.

If you notice anything resembling cyanobacteria, please refrain from wading, swimming, or drinking the water. Keep all pets out of the water and contact NHDES immediately. Please call NHDES to report a cyanobacteria bloom at (603) 848-8094 or email HAB@des.nh.gov.