Harmful Algal Blooms


HAB Recreational Use Advisories Issued by Wyoming Department of Health


What are harmful algal blooms? Harmful algal blooms (HABs) are dense concentrations of cyanobacteria or blue-green algae that pose a risk to human, pet, and livestock health. Under normal conditions, cyanobacteria are present at low levels and play an important role in aquatic ecosystems. Additional resources on HABs in Wyoming: informational flyer and video; and June 2018 webinar slides and recording.

What do HABs look like? When HABs occur, cyanobacteria become visibly abundant and can look like grass clippings, bluish-green scum or spilled paint on the water surface. To view pictures of harmful algal blooms in Wyoming click here.

Why are they harmful? Cyanobacteria blooms can produce poisons called cyanotoxins and may be associated with other irritants that can cause several health effects in humans, pets, and livestock. Health effects include rashes, itching, numbness, nausea, fatigue, disorientation, abdominal pain, vomiting, and diarrhea. For more information on HAB-related health effects: Centers for Disease Control and Prevention. In extreme cases, cyanotoxins may lead to pet or livestock death. Blooms may also cause fish kills and interfere with drinking water supplies. Additional information: US Environmental Protection Agency

What should I do if I suspect a HAB? Report the suspected HAB to the Department of Environmental Quality (DEQ) at 307-777-7501 or by clicking on "Submit a Complaint" on the Report a Spill webpage: http://spills.adm.apps.deq.wyoming.gov/ so that DEQ can investigate. If DEQ has not yet investigated an algal bloom, the Wyoming Department of Health and Wyoming Livestock Board recommends that you err on the side of caution and do the following:

  • Avoid contact with the water in areas where algae form scums.
  • Do not drink the water; boiling, filtration and/or chlorination will not make the water safe.
  • Caution should be taken when eating fish as health effects remain unknown. Rinse fish with clean water and eat only the fillet portion.
  • Do not breathe water spray in areas of the bloom.
  • Keep pets and livestock away from the water. Do not allow animals to drink the water, eat dried algae, or groom themselves after playing in the water.

Who do I contact if I or someone I know came into contact with a potential HAB or is experiencing an illness associated with a potential HAB? Rinse off with fresh water and contact a doctor or Wyoming Poison Control Center at 1-800-222-1222.

Who do I contact if a pet or livestock is experiencing an illness that may be associated with a HAB? Rinse the pet or livestock with fresh water and contact your veterinarian.

What will DEQ do when a HAB is reported? DEQ will perform preliminary screenings to determine if the bloom consists of harmful cyanobacteria. If harmful cyanobacteria are present, DEQ will collect samples using standard operating procedures and determine if toxins and/or the amount of cyanobacteria are at unsafe levels. DEQ will notify the Wyoming Department of Health if toxins and/or the amount of cyanobacteria exceed unsafe levels so an Advisory can be issued. The Advisory will be posted around the water body and include recommendations on how to keep people and animals safe. DEQ will coordinate with the Wyoming Department of Health and the water management agency to monitor the bloom until the toxins and/or the amount of cyanobacteria return to safe levels. DEQ investigated three potential HABs in 2017; summaries of these events can be found in the Resources table below.

What causes HABs? Cyanobacteria can be thought of as small floating plants. When there is sunlight, warm temperatures, and abundant food (nutrients such as nitrogen and phosphorus), cyanobacteria will grow rapidly while in slow or still water. Excess nutrients can come from stormwater, agriculture, wastewater, household activities, atmospheric deposition, and natural sources.

What is DEQ doing to reduce the frequency of HABs? DEQ has partnered with agencies, organizations, and members of the public to discuss ways to address nutrient pollution in Wyoming. This group, the Wyoming Nutrient Work Group, has worked with DEQ to develop the Wyoming Nutrient Strategy. The strategy identifies priority items for addressing nutrient pollution through development of numeric water quality criteria for nutrients, point sources, nonpoint sources, as well as education and outreach.  

What can I do help reduce the frequency of HABs?

  • Report problems when you find them. This will ensure that DEQ is aware of problem areas.
  • Participate in the Wyoming Nutrient Work Group and help provide DEQ with input on how to most effectively address nutrient pollution.
  • Be aware of potential contributions from your own home; use the recommended amount of fertilizer on your lawn, use phosphorus-free detergents, fix leaky septic systems and pick up pet waste. 

Additional photos of HABs and information about identifying HABs can be found at the following links:


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