Risks Associated with Harmful Cyanobacterial Blooms (HCBs) Continue Despite Cooler Temperatures

HCBs at Ocean Lake, Summer 2023

CHEYENNE, Wyo – Although fewer people are recreating in Wyoming’s lakes and reservoirs this fall as water and air temperatures decrease, the Wyoming Department of Environmental Quality (WDEQ), Wyoming Department of Health (WDH), Wyoming Livestock Board (WLB), and local, state, and federal partners want to remind people, including hunters and fisherman, to continue to avoid and keep animals away from harmful cyanobacterial blooms (HCBs) that may be present. Although most blooms occur during the warmer months and blooms are expected to dissipate as temperatures decrease, some types of cyanobacteria are known to persist in freezing conditions and may continue to pose health risks to people and animals.

Consistent with Wyoming’s HCB Action Plan, WDEQ concluded HCB sampling at the end of October. Despite the discontinuation of sampling, recreational use advisories 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 concentrations are below recreational use thresholds or December 31st, whichever comes first. The webmap will be updated as the status of advisories change. Listserv notices will be sent in the event any new recreational use advisories are issued.

For waterbodies with blooms, the WDH and WLB 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.

Questions about health effects and recreational use advisories can be directed to Courtney Tillman, Surveillance Epidemiologist, WDH, at courtney.tillman@wyo.gov or (877) 996-9000. Questions regarding cyanobacteria sampling can be directed to Kelsee Hurshman, Natural Resource Analyst, WDEQ, at kelsee.hurshman1@wyo.gov or (307) 777-2073.

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

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