DEQ issues caution for algae bloom

SEELEY LAKE – Based on photos received Oct. 18, the Department of Environmental Quality confirmed blue-green algae was present along the east shore on the north end of Seeley Lake. While not all blue-green algae blooms are harmful, the public is asked to use caution when recreating in Seeley Lake because conditions can change rapidly and are unpredictable.

Algae are a group of photosynthetic organisms which have a number of beneficial uses. However, algae may cause a great deal of damage if profuse growth results. Blue-green algae are particularly bothersome because it can ruin recreational areas because of their odors, toxins and dense, matted growths.

A 1984 report by University of Montana Professor Richard Juday and UM chemist Edward Keller mentioned heavy summer blooms on Seeley Lake in 1968, 1969 and 1970.

A report by the Lolo National Forest released in the fall of 1979 reported that Seeley Lake experienced occasional algae blooms in September or October. One of the dominant algae species found was blue-green algae and it said it is potentially toxic in bloom proportions.

Retired fish/aquatic scientist Bruce Rieman wrote in an email that he has never seen a blue-green algae bloom on Seeley Lake.

"We noted more modest accumulations of green algae and diatoms, but never thought those were abnormal for a lake in the general state (mesotrophic) that we have documented for Seeley," wrote Rieman who has worked with Clearwater Resource Council's lake monitoring for many years.

In general increasing nutrient input and increasing temperatures contribute to the higher prevalence of algae blooms. Conditions can change rapidly based on wind and temperature making blooms very unpredictable. During the colder winter months harmful algal blooms are uncommon.

Dr. Vicki Watson of the University of Montana Watershed Health Clinic, working with the Clearwater Resource Council, released a report called "Lake Water Quality, Tropic Status and Potential Loading Sources for Clearwater Lakes" in May 2012. It summarized information from the early 1970s through work done into the early 2010s.

The report indicated that Seeley Lake is mesotrophic, a waterbody with moderate level of biological productivity, in moderately good condition and has not changed measurably since the 1970s. However, Rieman noted that there was also no noticeable improvement in water quality that was anticipated given the decline in heavy logging and mitigation of road effects.

Rieman wrote that continued or increased inputs of nitrogen likely won't precipitate a blue-green algae bloom since blue-green algae are nitrogen fixers.  But increases in biologically available nitrogen from sources including septic contamination, fires, forest management and lawn fertilizers can increase production of all the other plants and algae. When they die, they decompose and use up oxygen. If the bottom of the lake goes anoxic, with no or very low amounts of dissolved oxygen in the water which has been observed in parts of Seeley Lake, this leads to a release of phosphorous from all sediments settled on the bottom of the lake. This is called a tipping point, defined as a sudden shift in the lake's behavior after years of accepting human disturbance with little visable change. It is very difficult to return the lake to its earlier condition once it has passed that tipping point even after external loading is reduced.

When DEQ received photos of the bloom at the north end of Seeley Lake Oct. 18, they visually confirmed the presence of blue-green algae. Resources were unavailable to deploy monitoring in the area.

"It is important to understand that conditions can change rapidly," wrote Hannah Riedl, DEQ Water Quality Specialist, in an email. "If we monitored for toxins immediately after the report and found no toxins, that does not preclude the possibility that the very next day (or hours later!) toxins could be present. This is why we always advise: when in doubt, stay out."

The Seeley Lake Ranger District posted Caution signs Oct. 18. DEQ advises to avoid water where they see evidence of a bloom or recent bloom (such as algae staining on rocks) for at least two weeks after the bloom has dissipated. People, pets and wildlife can become ill from contact, ingestion or inhalation of cyanotoxins. Reports of pet and livestock death from harmful algal blooms have been reported for decades. However, there have been no reports of animal or human sickness or death that Riedl is aware of from the reported bloom on Seeley Lake.

Riedl said she is not aware of anything specific that would have caused the bloom in Seeley Lake this year. She added this is the first report of a blue-green algae bloom reported on Seeley Lake since DEQ started tracking reports in 2017.

"One thing that any homeowner around the Seeley-Swan chain of lakes can consider to help remedy this problem is septic system maintenance," wrote Riedl. "These can be a large source of nutrients if not properly maintained."

For more information, to view pictures of harmful algae and to report suspected harmful algae blooms visit hab.mt.gov. DEQ can help confirm what someone is seeing and tell them what to do.