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Cyanobacteria in Vermont

Cyanobacteria (also known as blue-green algae) are common native algae in lakes, ponds and rivers around the world.  In Vermont, they can be found in any waterbody or river.  Some species of cyanobacteria produce toxins and these toxins have been documented in some Vermont waters.   Not all blooms will be toxic.  Specialized tests are required to tell whether a particular occurrence of cyanobacteria is actually producing toxins.  You cannot tell by looking.

The Watershed Management Division has worked with the Vermont Department of Health and the University of Vermont to develop protocols for responding to cyanobacteria.  While most occurrences of cyanobacteria associated with toxins have been on Lake Champlain, toxins have been detected in other waterbodies around the state. 

Identifying Algae that may pose a risk of toxins

Because of the large number of water bodies and the ecology of these organisms, we depend on our staff and the public to inform us of possible cyanobacteria blooms.  A visual assessment of algal abundance is made by the collector and a microscopic examination confirms whether potentially toxic cyanobacteria are present.  Toxin testing is conducted if densities of potentially toxic cyanobacteria are high.  Appropriate warnings and closures are then issued by the Health Department or local officials.  Monitoring and testing continue if the algae persist.

Play it safe – learn to recognize and avoid these algae

To report a cyanobacteria bloom, call

1-800-439-8550 (the VT. Dept of Health)


(802) 490-6130 (the Watershed Management Division)

Cyanobacteria along shore Scum on water surface
Quick Links


Cyanobacteria Guidance for Vermont Communities (pdf, 893KB)

Current algae conditions in Vermont

Basic information about cyanobacteria (pdf 283 KB)

Photo Gallery

What to do if you suspect a bloom (pdf 219 KB)

What causes algae blooms?(pdf 219 KB)

Other sources of information about cyanobacteria (pdf 41 KB)






Cyanobacteria along shore

VT DEC Watershed Management Division 1 National Life Drive, Main 2  Montpelier, VT  05620-3522  Tele: 802-828-1535   Fax: 802-828-1544

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