Harmful algae bloom identified west of Flathead Lake

An algal bloom that can sicken people or pets has been confirmed in Lake Mary Ronan, near the northeast shoreline of the lake just west of Flathead Lake, warned officials with Lake County Environmental Health.

According to the health department, a local reported the algae and county officials collected several water samples on Aug. 7. Oscillatoria, a type of harmful algal species that can produce toxins known as cyanotoxins, was identified in one of the samples from the northeast shoreline.  

No cyanotoxins were detected in the samples. Cyanotoxins can be produced at any time when a bloom is present and remain in the water column even after the bloom has visually dissipated. 

Health officials advised people to not drink, swallow or swim in water that shows signs of a harmful algal bloom, and to keep children, pets and livestock out of the water.  

Direct contact, ingestion or inhalation of the toxins may irritate the skin, eyes, nose, throat and respiratory system, or cause nausea, vomiting, diarrhea, headache, dizziness, muscle weakness or liver and kidney damage.  

If a person or animal contacts the bloom, they should rinse off with tap water immediately. 

If illness is suspected, call a health care provider or veterinarian or poison control. 

Harmful algal blooms most often occur in Montana’s reservoirs and lakes. Common characteristics include green, blue, light brown or gold coloration and the appearance of grass clippings or paint spilled on the water’s surface. 

Harmful algal blooms happen when cyanobacteria, also known as blue green algae, rapidly grow out of control. These organisms are native to Montana and are naturally found at low, safe densities in many freshwater systems. The blooms typically form when there are lots of nutrients available and when the wind is calm and sky is clear. They do not always release toxins. Water sampling is the only way to determine if toxins are present. 

The Montana Department of Environmental Quality and Department of Public Health and Human Services maintain a website where people can submit and view reports of suspected blooms at HAB.mt.gov.  

State agencies will work with the local jurisdiction to sample for the presence of toxins and monitor the incident. Recreationalists may check the website and view the map of reported blooms, health advisories, and information associated with reports. The site also has photos and information on how to identify a HAB.