Harmful Cyanobacterial Bloom (HCB) Recreational Use Advisory Lifted: Keyhole Reservoir

Wyoming Department of Environmental Quality  | view as a webpage

Wyoming Department of Environmental Quality

Harmful Cyanobacterial Bloom (HCB) Advisory Lifted: Keyhole Reservoir

The Wyoming Department of Health has lifted the recreational use advisory for Keyhole Reservoir because the harmful cyanobacterial bloom (HCB) that was present at the reservoir has dissipated and cyanotoxins were not detected in samples collected at the reservoir.

HCBs are also referred to as harmful algal blooms (HABs) since cyanobacteria are commonly known as blue-green algae. The Department of Health issues advisories to notify the public that there may be health risks for people and animals in areas where HCBs occur. Lakes and reservoirs under a recreational use advisory are not closed since HCBs may only be present in certain areas of the waterbody and conditions can change frequently. Advisories remain in place until blooms fully dissipate and cyanotoxin concentrations are below recreational use thresholds identified in Wyoming's HCB Action Plan. The status of advisories in Wyoming as well as other HCB resources can be found at WyoHCBs.org.

The bloom at Keyhole Reservoir was observed by ice fisherman and reported to the Wyoming Department of Environmental Quality (WDEQ). WDEQ visited the reservoir on March 8th to collect water samples near Wind Creek. Cyanobacteria densities exceeded the 20,000 cells/mL recreational use threshold identified in Wyoming’s HCB Action Plan, however, cyanotoxins were not detected in the samples collected on March 8th. WDEQ visited the reservoir again on April 13th and collected additional cyanotoxin samples near Arch Rock Campground. There was no visual evidence of a bloom and cyanotoxins were not detected in the samples that were collected. Staff at Keyhole State Park confirmed on May 6, 2021 that there was no evidence of a cyanobacteria bloom at Coulter Bay, Rocky Point, Tatanka Campground, or Wind Creek.

If you encounter a potential HCB, the Wyoming Department of Health and 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.

Questions about health effects and recreational use advisories can be directed to Courtney Tillman, Epidemiologist, Wyoming Department of Health, at courtney.tillman@wyo.gov or (307) 241-2319.

Questions regarding cyanobacteria sampling can be directed to Lindsay Patterson, Surface Water Quality Standards Coordinator, Wyoming Department of Environmental Quality, at lindsay.patterson@wyo.gov or (307) 777-7079.