Cyanobacteria (Blue-Green Algae) Conditions

Cyanobacteria (Blue-Green Algae) Conditions

cyanobacteria bloom

Cyanobacteria, also known as blue-green algae, are naturally found in fresh water in the U.S. and in Lake Champlain and other Vermont waters. Some types of cyanobacteria can release natural toxins or poisons (called cyanotoxins) into the water, especially when they die and break down. People and pets should stay away from cyanobacteria blooms. Learn more about cyanobacteria

For information on other monitoring locations and reports from earlier this season, check the Cyanobacteria Tracker Map

Information on lake conditions is provided by a network of volunteers trained and coordinated by the Lake Champlain Committee and by scientists from the Vermont departments of Health and Environmental Conservation. Monitors submit weekly visual observations of water conditions from sites around Lake Champlain.

Weekly Summary of Cyanobacteria Conditions

Below you can find information on where monitors and the public have reported seeing cyanobacteria this week. Everyone, especially people in these areas, should watch for and avoid cyanobacteria.

“Low Alert” means that small amounts of cyanobacteria were observed. “High Alert” means that large amounts of cyanobacteria were observed with dense scums or highly colored water.

It's important to know what cyanobacteria blooms look like so you can stay away from them.

Cyanobacteria Reports Received This Week - Updated September 24, 2021

 Crater Club   Lake Champlain   Essex, NY  9/22/2021 Low Alert
 Carmi DEC01- Central Open Water   Lake Carmi   Franklin  9/22/2021 Low Alert
 Carmi DEC03- Northeastern Open Water   Lake Carmi   Franklin  9/22/2021 Low Alert
 Lake Carmi State Park   Lake Carmi   Franklin  9/20/2021 Low Alert
 Lake Carmi State Park - Area B   Lake Carmi   Franklin  9/20/2021 Low Alert
 LTM 40   Lake Champlain   St. Albans Town  9/20/2021 Low Alert
 Newport Marina   Lake Memphremagog   Newport  9/19/2021
Low Alert
Low Alert


If you are interested in becoming a volunteer monitor on Lake Champlain, reach out to the Lake Champlain Committee at If you are interested in monitoring on a different Vermont lake, reach out to Peter Isles at

identifying cyanobacteria

It's important to know what cyanobacteria look like and to use your best judgment when thinking about swimming or doing other activities in the water. See photos of what cyanobacteria look like and what are not cyanobacteria.

Watch a video to help you identify cyanobacteria

Weekly drinking water test results

All 22 public drinking water suppliers on Lake Champlain submit samples for cyanobacteria toxin analysis. Drinking water test results are updated weekly by the Vermont Department of Environmental Conservation.

See the drinking water test results

Partners in Monitoring Vermont’s Waters

  • Lake Champlain Basin Program – funds cyanobacteria monitoring in the Lake Champlain Basin.
  • Lake Champlain Committee (LCC) – since 2003, coordinates and trains a group of citizen volunteers to monitor shoreline sites on Lake Champlain in Vermont, New York, and Quebec. You can reach out to LCC if you are interested in becoming a volunteer monitor.
  • Vermont Department of Environmental Conservation – monitors long-term water quality at dozens of off-shore stations on Lake Champlain and recruits and trains volunteers on many other Vermont lakes.
  • Vermont State Parks – monitors conditions at park swim areas.

to report a bloom:

Report a bloom to the Health Department by filling out this form. Include several photos and note the location of the bloom. (Taking pictures of water is difficult with glare and reflections. Take more pictures than you think you need!)