News from the New Hampshire Department of Environmental Services DATE: 09/22/2022

CONTACT: Kate Hastings, (603) 848-8094, HAB@des.nh.gov Cyanobacteria Bloom Alert for

Lake Warren in Alstead, NH

Concord, NH- A cyanobacteria bloom has been observed on Lake Warren. Cyanobacteria activity was first observed over the weekend on 9/17/22. The bloom dissipated before Monday, so a sample was not reviewed. The bloom material reappeared on 9/21/22, and a concentrated bloom sample from those aggregations had cyanobacteria cell concentrations (Dolichispermum) around 1 million cells/mL in several locations around the lake. An advisory would be issued, but the heavy rains today have caused the bloom material to dissipate. Please continue to report changing cyanobacteria conditions to HAB@des.nh.gov, and we will coordinate resampling as needed. It is possible this bloom will reform over the coming days. Remember, when in doubt stay out!

This message serves a local “Alert” for lake-goers to be on the lookout for accumulations of cyanobacteria, especially nearshore of the lake.

Advisories are issued once samples are collected and cell concentrations of cyanobacteria are confirmed to exceed 70,000 cells/mL of lake water.

NHDES advises lake users to avoid contact with the water in areas experiencing elevated cyanobacteria cell conditions, also known as a bloom. NHDES also advises pet owners to keep their pets away from cyanobacteria blooms.

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 may 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 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.

Visit the NHDES Harmful Algal and Cyanobacteria Bloom Program website for photos and more information about cyanobacteria at: Harmful Algal Blooms | NH Department of Environmental Services. Check out the Beach Mapper Website and follow the Beaches Twitter feed for updates on cyanobacteria advisories.

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.