WDEQ warns that risks associated with Harmful Cyanobacteria Blooms (HCBs) continue despite cooler temperatures

As water and air temperatures drop, fewer people are recreating on Wyoming’s lakes and reservoirs. However, the Wyoming Department of Environmental Quality (WDEQ), Wyoming Department of Health (WDH), and Wyoming Livestock Board (WLSB), in collaboration with partners, want to remind the public, including hunters and anglers, to continue avoiding harmful cyanobacteria blooms (HCBs) and to keep animals away from them.

While most blooms occur during warmer months and typically decline as conditions cool, some types of cyanobacteria can survive freezing temperatures and may still pose health risks to people, pets, and livestock.

HCBs, commonly referred to as blue-green algae, are dense concentrations of naturally occurring cyanobacteria. They can produce toxins and other irritants that affect human and animal health. Blooms usually appear in mid-to-late summer and can occur in streams, rivers, lakes, and reservoirs. Their appearance varies – they may be green, tan, brown, or blue-green, and can float in or on the water. They can look like spilled paint, clumps, grass clippings, or scum. They may also stick to underwater surfaces like rocks, plants, or debris, appearing as films, mats, or jelly-like balls.

Cyanobacteria are naturally present in surface waters at low levels, but under certain conditions such as warm temperatures, calm water, abundant sunlight, and excess nutrients, can rapidly multiply and form blooms. This year, Wyoming experienced a combination of factors, including below-normal snowpack and precipitation, and warmer than average air temperatures, which contributed to lower water levels and warmer surface waters earlier in the season. Along with increased public awareness and reporting, these combined conditions may have contributed to more frequent and earlier bloom events being detected across the state.

As of October 1, 43 waterbodies in Wyoming have Bloom Advisories. Of these, nine also have Toxin Advisories for specific locations.

Consistent with Wyoming’s HCB Action Plan, WDEQ will wrap up HCB sampling at the end of October. Even after sampling ends, recreational use advisories will continue to be in place for a number of waterbodies, as shown on the Wyoming HCB advisory webmap. As outlined in the Action Plan, advisories will remain in place until blooms have fully dissipated and cyanotoxin levels are below recreational use thresholds, or until December 31^st, whichever comes first. The webmap will be updated as advisories change, and listserv notices will go out if any new recreational advisories are issued.

For waterbodies with blooms, the WDH and WLSB continue to recommend the following:

• Avoid contact with water in the vicinity of the bloom, especially in areas where cyanobacteria are dense and form scum.
• Do not ingest water from the bloom. Boiling, filtration, 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.

Seek medical attention or a veterinarian if a person or animal is sick after exposure to a cyanobacteria bloom. Questions about health effects can be directed to Courtney Tillman, Surveillance Epidemiologist, WDH, at courtney.tillman@wyo.gov or (877) 996-9000. Questions regarding cyanobacteria sampling and recreational use advisories can be directed to Rachel Eyres, Recreational Water Quality Coordinator, WDEQ, at rachel.eyres@wyo.gov or (307) 777-2073.

Additional waterbodies in Wyoming may be experiencing cyanobacteria blooms that have not yet been identified or reported to the WDEQ or WDH. Please report such blooms at WyoHCBs.org or WyoSpills.org.

For more information on HCBs and recreational use advisories in Wyoming, visit WyoHCBs.org.

Current HCB Recreational Use Advisories: