Toxic Cyanobacteria Bloom in the Virgin River and the Streams of Zion National Park

cyanobacteria growth underwater
Cyanobacteria colonies like this will grow on rocks, sticks, and sand. Note the ribbed texture.

NPS

Updated December 18, 2020

Summary

Since a reported pet fatality in July 2020, Zion National Park staff have monitored cyanotoxin-producing algal blooms in several water bodies inside park boundaries on a monthly basis. Cyanotoxins are still present in water bodies, however their concentrations are below the Danger Advisory thresholds in the North Fork Virgin River, Taylor Creek, and North Creek and are below Warning Advisory thresholds in LaVerkin Creek. With lower cyanotoxin concentrations, The North Fork Virgin River, Taylor Creek, and North Creek Danger Advisories will be downgraded to a Warning Advisory and LaVerkin Creek will be downgraded to a Health Watch.



How Does This Affect Your Visit?

  • Children are especially vulnerable to cyanotoxins - minimize risk by avoiding contact with water bodies.

  • Do not submerge your head in the water. Toxins can enter the body by swallowing water or through the nose, eyes, or open wounds.
  • Do not drink river water. Toxins cannot be filtered out by standard hiking filtration methods.

  • Pets must be kept on a leash, especially near water sources. If pets get into the river, remove them from the water immediately, rinse off their fur thoroughly, and monitor for symptoms of toxin poisoning. A dog can die in as little as 15 minutes from anatoxin-a poisoning.

  • Permitted waterbody activities, such as permitted canyoneering, are allowed. Permits are still required.

You can visit Utah Department of Water Quality (https://deq.utah.gov/water-quality/north-fork-of-the-virgin-river-algal-bloom-monitoring-2020) for the most up to date information and to learn more about cyanobacteria and algal blooms.

More Information About Cyanobacteria

Cyanobacteria of the genus Microcoleus, Tychonema, and Nostoc have been found in the North Fork of the Virgin River, North Creek, and La Verkin Creek. Colonies of cyanobacteria can be red, yellow, tan, green, brown, or black in color.

Some cyanobacteria produce dangerous nervous system toxins. When in abundance, toxin concentrations can elevate to levels that affect the health of organisms exposed to them, including people, pets, and livestock. Humans and animals can ingest varying amounts of the growth material and/or toxins. Even very small pieces of the cyanobacterial growth may contain enough anatoxin-a to cause medical emergencies. These pieces of bacteria may be hard to see or even invisible.


Children and dogs are especially susceptible to being exposed to anatoxin-a. Anatoxin-a can be absorbed through the eyes, nose, or mouth by swimming in or submerging accidentally into contaminated water. Symptoms include skin rash, salivation, drowsiness, tingling, burning, numbness, pain, incoherent speech, seizures, vomiting, and diarrhea.

Contact the Utah Poison Control Center at (800) 222-1222 with concerns about anatoxin-a poisoning and call 911 in the event of a medical emergency.

Standard recreational water filtration and disinfection techniques will not remove the toxins. Recreators in Zion National Park should filter and disinfect water directly from springs if needed.

Dogs must be kept on a leash. If a pet breaks away and gets into the river, remove them from the water immediately, rinse off their fur thoroughly, and monitor for symptoms of toxin poisoning. A dog can die in as little as 15 minutes from anatoxin-a poisoning. More information about the
danger to dogs from anatoxin-a.

More information on cyanobacteria and its health risks to humans can be found at these links:
EPA
Utah Department of Health

 
Scientist sampling cyanobacteria in the Virgin River
Scientist sampling cyanobacteria in the Virgin River

NPS

 
cyanobacteria growth on rock
Cyanobacteria forms shelves at the waterline including bulbous growths as seen here.

NPS

Last updated: December 18, 2020

Contact the Park

Mailing Address:

Zion National Park
1 Zion Park Blvd.
State Route 9

Springdale, UT 84767

Phone:

(435) 772-3256
Recorded park information available 24 hours a day. Phones are answered 9 am to 12 pm Mountain Time. You can also send your questions to us at zion_park_information@nps.gov.

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