ST. GEORGE — Toxic bacteria levels in the North Fork of the Virgin River in Zion National Park have reached “a level that poses a risk to recreators,” according to an update from the national park issued Tuesday.
According to the update posted to the park’s website and social media, park staff have been monitoring cyanobacteria and cyanotoxin levels within the North Fork of the Virgin River, as well as North Creek and LaVerkin Creek throughout the winter. While concentrations of the bacteria and its resulting toxin had lowered during the winter, that changed in March.
“In the month of March, detected toxin concentrations have increased in the North Fork of the Virgin River to a level that poses a risk to recreators,” according to the update.
This has prompted the issuance of a danger advisory for the North Fork of the Virgin River urging people to avoid contact with the water until further notice.
Advisories concerning the continuing presence of bacteria and toxins in LaVerkin Creek and North Creek also remain in place.
“Visitors should avoid primary contact (i.e. swimming or submerging your head) with water in North Creek and La Verkin Creek,” the park’s update further states. “Visitors should not filter drinking water from any streams in the park until further notice.”
Toxins can enter the body by swallowing water or through the nose, eyes or open wounds. Very small to invisible amounts of the bacteria may also hold enough toxin to be a health hazard.
The bacteria and associated toxins are being produced by algal blooms in the North Fork of the Virgin River and associated tributaries. While the blooms are a natural part of the environment at low levels, once an algal bloom appears in high concentrations, it can prove harmful to both humans and animals.
The presence of the toxin, known as anatoxin-a, in Zion National Park was originally detected in July 2020, following the death of a Husky puppy that played in the Virgin River while its owners visited the park. The dog died within an hour of coming into contact with the river water.
Utah’s risk thresholds for issuing a warning advisory for anatoxin-a is 15 parts per billion (ppb). Exposure to this level of the toxin can cause long-term illness. The state issues a danger advisory once toxin levels reach 90 ppb, at which it becomes capable of acute poisoning. Previous samples collected from parts of the river have shown concentrations of more than 550 ppb.
While the toxin levels recorded by national park staff were not released as a part of Tuesday update, they were nonetheless high enough to urge visitors to stay away from the North Fork of the Virgin River.
“Cyanobacteria may produce dangerous liver and nervous system toxins,” according to the Utah Division of Water Quality. “Symptoms include skin rash, salivation, drowsiness, tingling, burning, numbness, pain, incoherent speech, muscle contractions or twitching, vomiting, and diarrhea.”
Beyond Zion National Park, an update from the Division of Water Quality was made in late January. A map on the department’s website shows toxins remain present in the Virgin River between Springdale and Rockville. However, algal bloom monitoring has ended for the season and will pick up once more in the spring, according to the website.
For concerns about possible human exposure, call your physician or the Utah Poison Control at 800-222-1222. For concerns about possible animal exposure, contact a local veterinarian.
The public is encouraged to watch for signs of harmful algal blooms and report suspected blooms to DEQ at 801-536-4123.
Statewide algal bloom updates can be found online.
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