Algal blooms: What can we do about them?

On Oct. 31, the Seeley Swan Pathfinder published a story discussing the possible detection of toxic blue-green algae on Seeley Lake. The article provided a thorough discussion surrounding such algal blooms and why we should be concerned.

Unfortunately, algal blooms are not a new phenomenon in the Clearwater "Chain of Lakes" as Seeley, Placid and Salmon lakes have had documented algal blooms in the recent past, though not all of the blooms were documented as toxic. In 2017, Placid Lake experienced an Anabaena infestation and in 2013 Salmon Lake had an aphanizomenon flos-aquae bloom.

Anabaena are classified as cyanobacteria (microorganisms related to bacteria but capable of photosynthesis). Generally, cyanobacteria are found in waters that have lots of sun, nutrients and little wind or tide. Some species produce toxins that can cause irritation in humans, such as rashes and dizziness, while other species can be highly toxic to humans, wildlife and pets. Regardless of the type of algal bloom, such blooms may cause unwanted adverse impacts regardless of their documented level of toxicity.

For instance, in Placid Lake in 2017, thousands of dead flies were detected in the areas documented Anabaena with the blooms. For the average person, dead flies may not be a concern. In fact, if you are picnicking on a hot summer day, the loss of flies may not bother you at all.

However, the presence of the dead flies may have caused adverse impacts throughout the food chain. It is certainly possible that the native fish in Placid Lake ate some portion of those dead flies. The consumption of the dead flies may in turn be problematic for the other species up the food chain that then eat the fish that consumed the flies. It should be noted that actual impacts beyond the dead flies were not documented.

Although the Clearwater Resource Council (CRC) was able to take samples of the Placid Lake algal bloom in 2017 and document the infestation, we do not specifically know what caused the bloom, the impacts of the bloom, whether such blooms are increasing in frequency, and what, if anything, we can do to reduce the incidence of such blooms.

The reality is that the impacts of such algal blooms are not documented because we lack the resources to monitor the event post algal bloom. And trying to assess adverse impacts throughout the food chain is a highly complex and expensive undertaking. Moreover, the absence of baseline data further hamstrings us when trying to determine what is going on. More complete data sets are only available for Seeley and Salmon lakes, while other lakes such as Placid and Inez are lacking basic data sets.

CRC is fortunate to work with a dedicated team of volunteers to monitor lake clarity via the Adopt-a-Lake program. Currently, Adopt-a-Lake volunteers primarily collect commonly used measures of water clarity, such as secchi disk readings. Secchi disks are opaque disks, typically white, used to gauge the transparency of water by measuring the depth at which the disk is no longer visible from the surface. The assumption is made that measuring clarity is an indicator of water quality. The greater the depth of the secchi reading, the better the result.

Such clarity measures are indicative of the amount of algae production in the lakes. While some algae growth is normal and necessary to provide food for aquatic species, excessive algae growth causes undesirable water quality changes and can be an indicator of excessive nutrient loading (water pollution).

However, given fiscal constraints, the Adopt-a-Lake program currently does not collect baseline data which would allow us to better understand nutrient loads, such as chlorophyll-a, total dissolved nitrogen and phosphorous, dissolved oxygen, conductivity, turbidity, etc.

To address this deficiency, CRC is developing a strategy to obtain the needed baseline data for our key lakes. We anticipate launching this improved water quality monitoring program starting in the 2020 field season. Stay tuned as CRC will be unveiling its new program in the next couple of months!