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 June 7, 2022

Zion National Park continues to monitor monthly for the presence of harmful cyanobacteria and cyanotoxins. Zion staff take a “multiple lines of evidence” approach when using data to issue recreational advisories. Monitoring efforts have detected cyanotoxins harmful to humans and pets in the North Fork of the Virgin River, therefore, the North Fork of the Virgin River and all connected tributaries will be elevated to a Warning Advisory. A Health Watch remains in effect at La Verkin Creek and a Warning Advisory remains in effect at North Creek. During Warning and Health Watch advisories, recreators should avoid primary contact recreation such as swimming or submerging the head. Do not drink stream water anywhere in the park. Carry in water or filter directly from a spring source.

Toxin-producing cyanobacteria of the genera 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 yellow, tan, green, brown, or black in color. Toxins detected in Zion include anatoxin-a, nodularin, microcystin, and cylindrospermopsin.

 

Need to know about cyanobacteria

Children are especially vulnerable to cyanotoxins, so be mindful of where they go if you are near a body of water like the Virgin River.

  • Do not swim or put your head under the water anywhere in Zion National Park.
  • Keep dogs on a leash in and out of the water. Dogs are vulnerable to cyanotoxin exposure because they may bite or accidentally eat/drink material from potentially toxic algal mats. More information about the danger to dogs from toxic cyanobacteria.
  • Do not drink any water from streams or rivers in Zion National Park. There is no known recreational water filtration method that is effective at removing cyanotoxins. If you must filter water for drinking while in the Wilderness, filter and disinfect it directly from a spring.

  • Contact the Utah Poison Control Center at (800) 222-1222 with concerns about cyanotoxin poisoning and call 911 in the event of a medical emergency. Symptoms can include, but are not limited to, skin rash, salivation, drowsiness, tingling, burning, numbness, pain, incoherent speech, seizures, vomiting, and diarrhea.

  • Some permitted activities, such as technical canyoneering, are allowed. Permits are still required. Check with the Wilderness Office at zion_park_information@nps.gov or 435-772-0170 for more information.

Learn more about toxic cyanobacteria from:

 
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: June 7, 2022

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Contact Info

Mailing Address:

Zion National Park
1 Zion Park Blvd.

Springdale , UT 84767

Phone:

435-772-3256
If you have questions, please email zion_park_information@nps.gov. Listen to recorded information by calling anytime 24 hours a day. Rangers answer phone calls from 1 p.m. to 5 p.m. MT, but a ranger may not answer if they are already speaking with someone else.

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