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

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

NPS

Updated November 4, 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 harmful cyanotoxins in North Creek which is elevated to a Danger Advisory. Toxin producing cyanobacteria has been detected in the North Fork of the Virgin River which will remain at a Warning Advisory. Toxin-producing cyanobacteria has been observed in La Verkin Creek which will remain a Health Watch. During Warning and Health Watch advisories, recreators should avoid primary contact recreation such as swimming or submerging the head. During Danger advisories, recreators should consider avoiding all direct contact with the water. Do not drink stream water anywhere in the park. Carry in water or filter and disinfect 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 [phone] 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 [e-mail] or 435-772-0170 for more information.

Learn more about toxic cyanobacteria from:

• Utah Department of Water Quality
• Utah Department of Health

• U.S. Environmental Protection Agency (EPA)

 

Scientist sampling cyanobacteria in the Virgin River

NPS

 

Cyanobacteria forms shelves at the waterline including bulbous growths as seen here.

NPS