The Gallatin County Health Department closed a pond in the Sundance Springs Subdivision on July 9, 2020, because of a toxic algae bloom. 

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The Gallatin City-County Health Department and the Sundance Springs Homeowners Association have closed a pond near East Graf Street and Rain Roper Drive after discovering a toxic algal bloom that may have contributed to a dog’s death, according to a county news release.

Recreational activities, such as swimming, kayaking and paddle-boarding, are no longer permitted at the privately owned pond, which sits next to the Sourdough trail system and is widely used by the public.

The health department also recommends pets and livestock be kept away from the water.

Ingestion of the contaminated water can cause muscle twitching, staggering, convulsions, paralysis and death. Those who have consumed the water or have pets that may have ingested the water and are experiencing symptoms should seek medical or veterinary attention immediately.

A dog’s death on Sunday may be connected to the toxic algal bloom. Given the presence of toxins in the pond and the dog’s young age, it’s likely the toxins caused the death, said Hannah Riedl, with the state Department of Environmental Quality's watershed protection section. However, an autopsy wasn’t performed, so the cause of the dog’s death isn’t certain.

The Gallatin City-County Health Department learned of the toxic algal bloom on Tuesday, said environmental health director Lori Christenson.

The health department conducted a preliminary test on Wednesday of the pond for microcystin and anatoxin, two toxins that can be produced by some freshwater cyanobacteria — or blue-green algae.

The test indicated there wasn’t any microcystin in the pond, but there was at least 2.5 micrograms per liter of anatoxin.

The presence of anatoxin led the subdivision and the health department to close the pond.

On Friday, the health department collected water samples from the pond to determine the exact concentration of anatoxin. The samples must be frozen and will be sent to the U.S. Environmental Protection Agency on Monday, Christenson said.

Cyanobacteria naturally occurs in freshwater ecosystems. Warm temperatures and excess nutrients, which can come from fertilizers, can cause blooms. Not all algal blooms are toxic. Additional information about harmful algal blooms is available on the Department of Public Health and Human Services website.

Going forward, the health department will likely continue to collect water samples from the pond.

“Our goal is to see no anatoxins,” Christenson said.

The health department will notify the public if the conditions at the pond change.

Those with questions or concerns can call the environmental health services at the health department at 406.582.3120 or can email the division at EHS@gallatin.mt.gov.

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Perrin Stein can be reached at pstein@dailychronicle.com or at 582-2648.

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