Toxic algae found in Lake Mary Ronan

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. 

An official with the Montana Department of Environmental Quality (DEQ) reported that as of Tuesday, no sickness had been reported by local residents or campers at the state park. 

Tiffany Lyden, Education and Outreach Specialist, said. DEQ has been coordinating with the staff at Lake Mary Ronan State Park to post caution signs at the entrance and swimming area to let visitors know about the risks and has provided information to Friends of Lake Mary Ronan to distribute. 

She also said that according to the Lake Mary Ronan State Park office, “it sounds like there is still a harmful algal bloom occurring.  The water was described as murky with a swampy smell and yellowish coloration.”

“The state park is currently advising visitors not to swim at the beach, and keep their pets out,” she added.  

Health officials advise 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.

No cyanotoxins were detected in the water samples taken last week. 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.

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.

Excess nutrients can cause algal blooms

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.

Conditions that can lead to harmful algal blooms are excess nutrients (like phosphorus and nitrogen), abundant sunlight, warm temperatures, and stagnant or slow-moving waters. 

“Mid to late summer and into early fall are when we tend to see harmful algal blooms on Montana lakes, ponds and reservoirs,” Lyden said. 

She added that excess nutrients in waterways can come from lawn and agricultural fertilizers, septic systems, stormwater runoff from streets and neighborhoods, and wastewater treatment plants.

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.

Lyton said In most cases, harmful algal blooms die and disappear after a few weeks, but they can last longer. If a bloom has produced toxins, those can remain in the water column after a bloom has visually dissipated. 

“It’s a good idea to stay out of those areas until there has been no visible bloom for two weeks,” she added. “Algal blooms can naturally die off or wind or rain can sometimes cause them to break up and dissipate.”

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 health department 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.