Health Officials Confirm Clark Fork River is Free from Algal Bloom Toxins

llowing additional testing by state agencies, officials with the Missoula City-County Health Department can confirm there is no significant presence of cyanobacteria or algal blooms in the Clark Fork River.

The Missoula City-County Health Department (MCCHD) and Missoula Valley Water Quality District received numerous calls earlier this month stemming from social media posts that reported dogs dying after swimming in the Clark Fork River. The social media posts indicated the area of concern was the Jacob’s Island Dog Park in Missoula.

After an initial news report stated the owner or veterinarian could not be reached to confirm the social media posts, a dog owner reached out to the health department to report that one of their dogs had passed away and their other dog was ill. The dogs had recently been to the Harper’s Bridge Fishing Access site off Mullan Road.

Staff visually inspected the Harper’s Bridge Fishing Access site and did not find indication of an algal bloom. However, due to heightened public interest and out of an abundance of caution, health department officials worked with the Montana Department of Environmental Quality (DEQ) and the Environmental Protection Agency (EPA) to sample for cyanobacteria and toxins. The results from DEQ stated there were no detectable toxins. Examination under a microscope revealed organisms common in slow-moving water, including zooplankton and algae and very low levels of a cyanobacteria species. The EPA samples also did not detect toxins.

The results are “totals” that represent combined toxins both outside and inside of cells. Water samples were further corroborated by veterinary results that did not indicate the dogs’ death and illness were associated with toxins from harmful algal blooms.

Water temperatures will continue to rise through August. If you and your family and pets plan to recreate in the river, you should inspect the water before kids and pets enter. Do not go into water that smells bad, looks discolored, or has foam, scum, dead fish or mats of algae on the surface. Harmful algal blooms or HABs can look like wet paint, paint splatter or pea soup. When in doubt, stay out! For more information visit HAB.mt.gov.