Cyanobacteria (Blue-Green Algae)

  The Cyanobacteria Tracker Map allows the public to check the recent cyanobacteria reports at shoreline sites and recreational swimming areas of Lake Champlain and various inland lakes in Vermont. At many sites, observations are made weekly from early June to early October. Sites are identified as "Generally Safe" or indicated as having cyanobacteria presence with "Low Alert" or "High Alert." 

Check the Cyanobacteria Tracker Map

• Stay away from water with a cyanobacteria bloom.
• Keep pets out of the water.
• Tell the lifeguard or manager on duty, if you are at a monitored beach.
• Report the bloom to the Health Department by filling out the Cyanobacteria Bloom Report 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!)
• If you have questions about a possible bloom on your private pond, email [email protected]. Include several pictures as well as an image of a map noting the location of the bloom. (Taking pictures of water is difficult with glare and reflections. Take more pictures than you think you need!)

High winds and large waves in the ocean are known to create aerosolized droplets that contain cyanobacteria. Scientists are not sure if cyanobacteria cells can become airborne on Vermont lakes, which have calmer conditions than the ocean.

Some activities — such as water skiing — may create droplets of water that can be breathed in. Those droplets could contain cyanobacteria cells during a cyanobacteria bloom. If aerosolized droplets are formed, it is not known how far the droplets carrying cyanobacteria cells could travel in the air. This would depend on the size, shape, density and other physical properties of the cyanobacteria cells.

Microcystins, the most commonly found cyanotoxins in the U.S., are large molecules that are not volatile, meaning they would not evaporate into the air from the water. Therefore, these molecules would only be breathed in if water droplets containing the toxin are created through wind, waves, boat motors, etc.

It is unknown whether anatoxin-a and cylindrospermopsin, which are other types of cyanotoxins, can volatilize from water.

The Health Department is one of many partners working to monitor cyanobacteria in Vermont:

• The Lake Champlain Basin Program funds cyanobacteria monitoring in the Lake Champlain Basin.
• The Lake Champlain Committee recruits, trains, and coordinates a large group of volunteer monitors in the Lake Champlain Basin.
• The Vermont Department of Environmental Conservation recruits and trains volunteers on many other lakes in Vermont.
• Staff at Vermont State Parks and many town beaches monitor conditions at swim areas at their parks.

Most of the time, cyanobacteria conditions are assessed visually. This means that staff or volunteers go out to a site, look at the water conditions, and report on whether they see cyanobacteria or not. This information is then reviewed and approved before it is displayed on the Cyanobacteria Tracker.

At select sites, water samples are also taken along with the visual observation. These water samples are then tested for cyanotoxins and analyzed to see which cyanobacteria are present and in what densities. In the past, the analyses done on the water samples have shown that where cyanobacteria are not visible to the naked eye, we don’t see elevated levels of toxins.

Cyanobacteria are not usually found in groundwater. If you have reason to believe that surface water is getting into your private groundwater well, you may wish to talk with a water treatment specialist or test your water for contaminants, including bacteria and nitrates.

We recommend not swallowing untreated lake or pond water in any way — including drinking, teeth brushing or food preparation. Untreated water may contain cyanobacteria or cyanotoxins, as well as other microorganisms and chemicals that can make you sick. We do not recommend showering or bathing in water that may contain cyanobacteria, because contact with cyanobacteria can cause rashes and skin irritation.

If your private drinking water comes from surface water, work with a water treatment specialist to make sure that your system can treat for cyanotoxins and other pathogens. 

The Health Department works with the Department of Environmental Conservation and public drinking water suppliers that use surface water to test for cyanotoxins in drinking water from July through the beginning of November. See the test results  

We recommend cleaning the fish properly and not eating organs—such as the liver—which may accumulate cyanobacteria toxins. During periods of blooms, anglers should not eat fish caught in a bloom to reduce exposure to cyanobacteria toxins.

We do not know how long cyanotoxins may remain in fish organs when fish swim in blooms.

Season summary maps go back to 2012. From each of those maps, you can download the raw data.

Annual monitoring reports are available from the Department of Environmental Conservation.

The Lake Champlain Basin Program has technical reports dating back to 2001 about the occurrence of cyanobacteria in Lake Champlain.

Beach managers should visually monitor the water on a routine basis.

If a cyanobacteria bloom is observed in a swim area, beach managers should close the swim area and post signs to prohibit wading and swimming. The swim area should remain closed for the duration of bloom. Keep in mind that cyanobacteria can regulate their buoyancy and may move down in the water column at night but reappear in the late morning or early afternoon the next day.

The day after the bloom has dissipated, the water may be sampled and taken to the Vermont Agriculture and Environment Laboratory for toxin testing. If results come back below the Health Department’s guidance levels, the swim area may be re-opened. If toxin testing is not conducted, it is recommended to keep the beach closed until water has been clear for a full 24 hours. 

Recreational water values

• Microcystin: 8 ug/L (micrograms per liter)
• Anatoxin-a: 8 ug/L
• Cylindrospermopsin: 15 ug/L

Drinking water values

• Microcystin: 0.3 ug/L
• Anatoxin-a: 0.5 ug/L
• Cylindrospermopsin: 0.5 ug/L

Cyanobacteria blooms are expected to continue to increase in the coming years due to climate change and more nutrients — nitrogen and phosphorus — running off into waterways. Lakes and ponds previously not impacted by blooms may experience blooms. The Health Department offers a tool and reference guide for communities experiencing cyanobacteria blooms. This guide is intended for lakes and ponds with new or sporadic appearances of blooms. It is not appropriate for guidance in heavily impacted areas. This guide is not a regulatory guide, a prevention manual, nor a practice for public water system operation.

Cyanobacteria Guidance for Vermont Communities

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BMAA is an amino acid produced by some cyanobacteria. Researchers are testing the hypothesis of a link between BMAA exposure and ALS. This research is very preliminary and has not been proven. The Health Department will continue to review information as it becomes available.