SPRINGDALE — Zion National Park is still asking visitors to take precautions nearly one month after a toxic cyanobacteria bloom killed a puppy that swam in the North Fork of the Virgin River on the Fourth of July.
Park spokesman Jeff Axel said there have been no documented cases of anyone, or any dog, becoming sick because of the cyanobacteria since the dog died. Nonetheless, he said, people in other instances have been sickened by anatoxin-a, the cyanotoxin produced by the bloom, and the park is currently advising guests to avoid contact with the Virgin River and La Verkin Creek until further notice.
Axel said the cyanobacteria, often called blue-green algae, is generally found in still bodies of water like lakes; Utah Lake is itself susceptible to a different kind of toxic algae bloom. Because this bloom was found in a river — for the first time in state history, Axel said — scientists are currently working to understand the recreational risk.
Jared Mendenhall, spokesman for the Utah Department of Environmental Quality, said the toxins are released when the blooms are "disturbed or kicked up."
Axel described the bloom as often appearing as a slimy yellow, tan or black ribbed substance that can coat rocks in the river. But pets and humans can be harmed by smaller or even invisible concentrations, according to the National Park Service; children and dogs are particularly susceptible to the toxins, it says.
The service describes symptoms of anatoxin-a exposure including "skin rash, salivation, drowsiness, tingling, burning, numbness, pain, incoherent speech, seizures, vomiting, and diarrhea." The cyanotoxin can be absorbed through the eyes, nose or mouth while submerged in water.
Though nearby Springdale draws its culinary water from the Virgin River, city officials told the St. George News the filtration system has thus far worked to keep the drinking water safe. It is being tested daily, Mendenhall added.
Axel said when it comes to the concentration of cyanotoxin in a body of water, 15 micrograms per liter is considered above normal and 90 micrograms is considered dangerous. The National Park Service says some samples taken in the North Fork on July 15 showed a concentration of more than 550 micrograms per liter.
Though Zion has not restricted access to The Narrows or other popular destinations that involve contact with the river, it has posted warning signs around the park and encourages visitors to contact poison control at 800-222-1222 with questions or concerns about exposure.
Axel said the park is hoping for some heavy rains to disperse the cyanobacteria from the river.