Cyanobacteria: Blue-Green Algae

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Report a Blue-green Algae Bloom

Call: 1-800-439-8550
Email: Environmental Health

Lake Condition Update

Blue-green algae bloom in Quebec Cyanobacteria, also referred to as blue-green algae, are a common and natural component of the microscopic plants (plankton) in Lake Champlain and other Vermont waters.


Why be Concerned about Blue-green Algae?

Some types of blue-green algae produce natural toxins or poisons. When these algae die and break down, toxins can be released into the water.

Cyanobacterial toxins may cause illness

There are no documented cases in Vermont of human illness related to blue-green algae, however, caution around the algae is urged.

Depending on the type, amount and route of exposures, different types of health effects can be caused by cyanobacterial toxins.

If you believe that someone has become ill because of exposure to blue-green algae, seek medical attention and contact the Health Department at 1-800-439-8550.

A danger to pets

Pet owners need to be mindful around algae blooms. If animals ingest the toxin, they can be quickly paralyzed and die. Signs of poisoning include weakness, staggering, difficulty breathing, convulsions and death.

During the summers of 1999 and 2000 the death of two dogs was attributed to blue-green algae poisoning, after drinking large amounts of contaminated water directly from the lake.

Blue-green algae can become very abundant in some sections of Lake Champlain once the water warms up in mid-summer. Particular problem areas are Missisquoi Bay and St. Albans Bay. Under calm conditions, blue-green algae can accumulate in thick layers at the surface or along the shoreline. These accumulations are frequently referred to as “blooms” or “scums.”

While blue-green algae toxins have been detected at many locations in Lake Champlain, the highest concentrations of toxins are usually found in blooms and shoreline scums. These dense accumulations pose the greatest potential health risks. Watch for dense accumulations of algae and avoid these areas. 

Learn more: Facts about Blue-green Algae

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Algae Blooms

Blooms generally have the following properties:

See photo examples of what is - and is not - blue-green algae

Weather influences where blue-green algae will accumulate. During extended periods of calm and sunny days, blooms can accumulate at the surface in any location. Wind and waves may cause them to form along shorelines or in protected areas. Shifts in wind direction can move a bloom from one location to another. Periods of cool rainy weather can often lead to the disappearance of a bloom.

Check current lake conditions

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Monitoring for Blue-green Algae

Cyanobacteria on Lake Champlain are monitored by joint efforts from the Lake Champlain Committee and the Vermont Departments of Health and Environmental Conservation.

taking a sample of a blue-green algae bloomLake conditions are reported during the summer months from state and volunteer monitors to the health department. We regularly update our website and interactive tracking map with these reports.

The Health Department, with local and state partners, began a pilot program in 2013 to get background information of cyanobacteria ecology at four inland lakes, Memphremagog, Carmi, Elmore and Iroquois. The same monitoring protocol used at shoreline sites on Lake Champlain will be used at these sites.

Partners in Monitoring Vermont's Waters

Lake Champlain Committee coordinates and works with a group of citizen volunteers to monitor shoreline sites on Lake Champlain. There is a higher risk for people or pets to come into contact with cyanobacteria at these locations, and generally the highest amounts of toxins can be found in shoreline scums.

Vermont Department of Environmental Conservation monitors long-term water quality at dozens of off-shore stations in Lake Champlain.

Drinking Water Test Results - All 22 public drinking water suppliers on Lake Champlain submit samples for analysis to identify any Blue-Green algae toxins. Laboratory test results are updated weekly by the Division of Drinking Water and Ground Water Protection.

The Big Picture

Our Vermont Environmental Public Health Tracking portal brings together in one place environmental and public health data, to help us better understand how environmental hazards can contribute to certain illnesses. The Vermont portal also supplies data to the National Tracking Network to address local environmental public health concerns.

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Guidance for Vermont Communities

Blue-green Algae Guidance for Vermont CommunitiesBlue-green Algae (Cyanobacteria)
Guidance for Vermont Communities
PDF document
The appearance of Blue-green algae (cyanobacterial) blooms is expected to continue to increase in the coming years. Lakes and ponds previously not impacted by blooms may experience 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.

The focus of this document is to ensure adequate protection of public and animal health when cyanobacterial blooms occur in lakes and ponds. Its intent is to assist local officials and other community members identify and respond to the cyanobacterial blooms so as to best protect public and animal health. This guide, however, is not a regulatory guide, a prevention manual, nor a practice for public water system operation.

Public Health and the Environment

Explore searchable data and information about the links between the environment and public health at our Vermont Environmental Public Health Tracking Portal.

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