Harmful cyanobacterial blooms (HCBs) are dense concentrations of cyanobacteria (photosynthetic single-celled microscopic organisms) that pose a health risk to people, pets, and livestock. Cyanobacteria are commonly referred to as blue- green algae because they look very similar to algae. For this same reason, HCBs are also commonly referred to as HABs.

Under normal conditions, cyanobacteria are present at low levels and play an important role in aquatic ecosystems. When HCBs occur, cyanobacteria become visibly abundant and can look like grass clippings, blue-green scum, or spilled pain on the water surface. HCBs may also be suspended in the water column, so HCBs may also make the water appear green or blue-green. To view photos of harmful cyanobacterial blooms found in Wyoming, click here.
Cyanobacteria can produce cyanotoxins and other irritants that can cause several health effects in people, pets, and livestock. Health effects include rashes, itching, numbness, fatigue, disorientation, abdominal pain, vomiting, and diarrhea. In extreme cases, cyanotoxins may lead to pet or livestock death. Blooms may also cause fish kills and interfere with drinking water supplies. More information on HCB-related health effects for people, pets, and livestock: Centers for Disease Control and Prevention
Report the suspected HCB to the Department of Environmental Quality (DEQ) at 307-777-7501 or by clicking “Submit a Complaint” on the Report a Spill webpage: WyoSpills.org so DEQ can investigate. If DEQ has not yet investigated a bloom, the Wyoming Department of Health and the Wyoming Livestock Board recommend the following:
  • Avoid contact with water in the vicinity of the bloom, especially in areas where cyanobacteria are dense and form scums.
  • Do not ingest water from the bloom. Boiling, filtration, and/or other treatments will not remove toxins.
  • Rinse fish with clean water and eat only the fillet portion.
  • Avoid water spray from the bloom.
  • Do not allow pets or livestock to drink water near the bloom, eat bloom material, or lick fur after contact.
  • If people, pets, or livestock come into contact with a bloom, rinse off with clean water as soon as possible and contact a doctor or veterinarian.
Rinse off with fresh water and contact a doctor or veterinarian. The Wyoming Poison Control Center can be reached at 1-800-222-1222.
If the bloom consists of harmful cyanobacteria, DEQ will collect samples to determine if cyanotoxins and/or the amount of cyanobacteria are at unsafe levels. If unsafe levels are present, DEQ will notify the Wyoming Department of Health so an Advisory can be issued. The Advisory will be posted around the waterbody and include recommendations on how to keep people and animals safe. DEQ will work with the Department of Health and the water management agency to monitor conditions until the bloom dissipates. Once a bloom has completely dissipated, the Wyoming Department of Health will lift the Advisory.
Cyanobacterial blooms are most commonly caused by excessive amounts of nitrogen and phosphorus from fertilizers, animal waste from pets and livestock, wastewater from treatment plants and septic systems, detergents, stormwater runoff, cars, and power plants. In addition, shallow water with abundant sunlight, warm temperatures, still or slow moving water, can also cause cyanobacteria to grow rapidly. Wind may also concentrate cyanobacteria.
DEQ has partnered with the Wyoming Nutrient Work Group, a stakeholder group comprised of agencies, organizations, and members of the public, to develop the Wyoming Nutrient Strategy. The strategy identifies priority items and next steps for addressing nutrient pollution through development of numeric nutrient criteria, reducing nutrients from point sources and nonpoint sources, and educating the public about nutrient pollution and its impacts.
  • 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.