‘Danger’ warning for North Fork of Virgin River in Zion remains after new testing

ST. GEORGE — Zion National Park released an update Sunday morning about the status of the cyanobacteria and threat of toxins in the North Fork of the Virgin River, warning visitors that the area remains in the “danger” category.

Keanna, the 5-month-old Siberian husky pup that died after being exposed to the cyanobacteria bloom in the north fork of the Virgin River, location and date unspecified | Photo courtesy of Zion National Park, St. George News

This report follows an incident that occurred on July 4, when the Utah Department of Environmental Quality’s Division of Water Quality and the National Park Service received a report from Zion National Park that a dog had died an hour after swimming in the North Fork of the Virgin River.

According to the release, the National Park Service is continuing to work closely with the Utah Department of Health and the Utah Division of Water Quality to assess the risk and better understand the conditions of the cyanobacteria that produce toxins found in some of the local streams.

The north fork of the Virgin River as seen from the beginning of The Narrows hike on the eastern outskirts of Zion National Park, Utah, July 1, 2015 | Photo by Hollie Reina, St. George News

The dog was exhibiting symptoms before dying congruent with exposure to cyanobacteria toxins, which included difficulty walking, pain and seizures. Monitoring of the cyanobacteria in the North Fork of the Virgin River began just days later on July 7.

The Utah Division of Water Quality said benthic cyanobacteria mats have been found in varying densities within the river from The Narrows to Confluence Park in LaVerkin.

So far, they have detected a very low concentration of anatoxin-a in the water column. Based on these concentrations, wading or incidentally/accidentally ingesting small amounts of water from the main watercourse (not near disturbed algal colonies) poses a very low risk, according to the statement. However, they are still recommending visitors to not drink from any surface water in the park. Water should only be filtered directly from a spring.

North Fork Virgin River, Springdale, Gateway to Zion | Dan Mabbutt STGnews.com
North Fork Virgin River, Springdale, Gateway to Zion National Park, Utah, Jan. 14, 2012 | Photo by Dan Mabbutt, St. George News

The low concentration observed in the water column affirms that the highest risk exposure scenario is from disturbing the colonies and incidentally ingesting pieces of the bacteria mat, which float.

According to the statement, benthic disturbance samples from last week indicate that the North Fork Virgin River is still in the “danger” category, with levels in excess of 550 parts per billion under this exposure scenario. Acute poisoning symptoms can appear at 90 ppb.

Melinda Bennion, a native aquatics biologist, told St. George News that having these types of toxins are part of natural occurrence for cyanobacteria and this isn’t currently thought to be a new thing. Their educated guess is that it has been in the stream systems.

“Some of them have toxins that are harmful and a lot of us think they’ve been in the water — it’s not a new thing,” she said. “It’s been out there but maybe not in that high of levels, or maybe because a dog has never eaten the algae it wasn’t known.”

Turbidity in the river does help to move algae, so storm events and higher flow events could help to flush the river, but she said those are questions for the Division of Water Quality. As a fish biologist, Bennion said they haven’t seen any effect on the fish.

“Like I said, I think it’s something that has been in the water for a long time.”

The Division of Water Quality provides the following measures to stay safe:

  • Don’t swallow water when swimming.
  • Wash hands with clean water before eating or preparing food.
  • Clean fish well and discard the guts.
  • Keep animals away.
  • Recognize the signs of a bloom, and when in doubt, stay out.

If you plan on visiting the Narrows or engaging in any activities along the Virgin River in the park, the Zion National Park Service encourages you to plan ahead and use your best judgment. Find specific testing results, precautionary and latest information here.

Copyright St. George News, SaintGeorgeUtah.com LLC, 2020, all rights reserved.

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