top of page


GCWIN’s field team are the boots on the ground for this program. Each week our field scientists go to zones on Grand Lake, Shadow Mountain Reservoir, Granby Reservoir, and Willow Creek Reservoir to monitor for harmful cyanobacteria. A weekly report is sent to water management entities, town officials, and other stakeholders to ensure local agencies and the public are informed.

Screenshot (3)_edited.jpg

What is Cyanobacteria?

Cyanobacteria is a type of photosynthesizing bacteria that occur in most bodies of water. In a healthy ecosystem, cyanobacteria creates oxygen which increases the amount of dissolved oxygen. However, under certain environmental conditions, they can cause what is known as harmful cyanobacterial blooms (HCBs), creating a thick green-blue film on the surface. HCBs can release toxins, called cyanotoxins, into waterbodies that have harmful effects on both humans and wildlife.

Many environmental conditions, both chemical and physical, may lead to HCBs, including but not limited to:

  • light availability

  • water temperature

  • nitrogen and phosphorus levels

  • changes in water flow

  • pH changes

  • trace metals

Because of the various different factors in play, it is difficult to predict when a bloom may occur. This is why it is so important to monitor popular recreational areas on a regular basis.

SMR-NOR2 Scope Image 6 07012022_edited_e

How does cyanobacteria affect the environment and me?

As noted above, HCBs cause harm to the health of the environment and us. Firstly, exposure (by skin or consumption) to the toxins released by HCBs can cause a variety of detrimental health effects, such as skin rashes, abdominal pain, headaches, diarrhea, and more. These effects are not unique to humans; other animals, like dogs, can experience these through exposure to cyanotoxins as well. 

Ecologically, these blooms have a large effect on the waterbody. The blooms decrease sunlight that reaches submerged plants, reducing the amount of oxygen. These low oxygen levels can cause high mortality rates throughout the food web, in fish, shellfish, invertebrate, and plant populations.

Identifying cyanobacteria

When the GCWIN field team notices what could be cyanobacteria in a body of water, they run a couple of field tests before moving forward with lab testing for toxin levels. Cyanobacteria functions differently from other types of algae. These preliminary tests are designed to help determine whether the matter present in the body of water is cyanobacteria or something else. 

These tests can be performed by anyone, and don't require any expensive materials to perform. Outlined below are how to run them and what to look for, should you come upon an algal bloom.

Stick Test

Cyanobacteria has a different structure from other types of algae that can bloom. Because of this, it appears different than non-toxic algae. To determine whether the bloom you see is toxic cyanobacteria or non-toxic algae, take a long stick and dip it into the bloom. If the green algal material hangs off the stick in strands, it is NOT cyanobacteria. If it adheres to the stick like paint, it is likely cyanobacteria. 

Jar Test

Cyanobacteria is a photosynthesizing bacteria and have developed the ability to control their buoyancy in water to ensure they always float at the top of the waterbody. To conduct this test, collect a water sample containing some of the algal material and place it on a flat surface. After 30 minutes with no agitation (do not move or shake the jar in any way), if cyanobacteria are present it should float to the top.

What do I do if I find cyanobacteria?

If you come across a waterbody where a cyanobacterial bloom could be occurring, please take a picture of the affected area, plus any additional pictures of tests, if they were performed. You can email those pictures to GCWIN at along with a detailed description of the location (coordinates would be greatly appreciated). 

It is always safer to stay cautious around what you think could be a bloom. Try to stay out of the water, and keep any pets you may have with you out of the water as well. If you or a pet is exposed through skin contact please rinse the exposed area with fresh, clean water. If you or someone you know ingest cyanotoxins, seek medical treatment IF adverse health conditions are observed.

Screenshot (4)_edited.jpg
Screenshot (4)_edited.jpg
bottom of page