OUR GEM: Smoke on the water

With more than a month of diminished air quality due to wildfire smoke this summer, you may be wondering whether smoke impacts extend beyond what we already know about human health: Where does the smoke end up? Does it affect ecosystems like Lake Coeur d’Alene?

Much more attention has been given to the downstream effects of fire on water, but there is growing interest in the downwind impacts of smoke on water bodies and water quality. 

While we tend to think of smoke as airborne ash, smoke is actually a complex cocktail of chemicals, minerals, metals and microbes. Depending on the when/what/where/how of the fire, the content of the smoke will vary. As the cloudy cocktail is carried away on the wind, larger stuff generally falls back to the ground closer to the fire source, but smaller materials can fly high for days or even months. Smoke plumes have been documented as traveling around the world, in some cases. The sky cruise most often ends for the smallest particles when a rain or snow rinse deposits them back on the land or in water.  

Smoke is like diluted compost blowing on the breeze with macro and micronutrients plus microbes. If the right growth enhancers are washed from the sky in the right place, a population explosion can occur. This is especially true when a previously limited resource, such as nutrients for microbes already in the water, is delivered.  

Algal blooms are not typical near the North Pole, so researchers went looking for an explanation for the unusual event that lasted throughout the summer of 2014. They linked the algal bonanza in the nitrogen-starved Artic Ocean to the delivery of nitrogen-rich smoke from burning peatlands in Siberia the same year. Similarly, following the Australian bushfires in 2019-2020, massive algal blooms in the Southern Ocean were traced back to the path of iron-rich smoke plumes.  

In some cases, a chemical signal may be detectable in the water such as the elevated potassium levels repeatedly measured in a river near Calgary, Alberta, Canada in years with more smoke. However, limited nutrients may also be gobbled up so fast that it’s nearly impossible to detect the chemical changes and hard to attribute any ecological effects to the "smoke fall."

While smoke can accelerate algal growth, it can also pump the brakes by throwing shade on the water. Reduced sun exposure means cooler temperatures and less fuel for photosynthesis. The shading effects are likely more pronounced and impactful when smoke is particularly thick or sticks around for a long time, but this is not well-studied. 

Perhaps the biggest remaining mystery about how smoke and water interact lies in the biological exchange. Do the microbes in smoke end up in the water? If so, do they change the microbiome of their new digs? Over the last few years, research at the University of Idaho Coeur d’Alene’s “Pyroaerobiology” lab has cataloged and cultured a variety of microbes from local smoke samples. The fact that thousands of living microorganisms can be collected from smoke and grown in the lab indicates that a diversity of smoke-borne microbes are likely traveling to destinations far from the fire, but we know very little about what happens along their journey and what happens when they arrive. Recent research has revealed that they can colonize soils and compete with existing microbes to change the composition of soil, but we know little about whether this is true for smoke microbes falling into our local lakes and waterways. Understanding these impacts only becomes more important as smoke season lengthens, but it’s important to remember that wildfires have been affecting our skies, lands and, likely, lakes for over 400 million years. It’s our understanding of the wide variety of wildfire impacts that is still ripe fruit for discovery.  

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Krista Bonfantine is a postdoctoral fellow with the University of Idaho Pyroaerobiology Lab. Leda Kobziar, Ph.D., is a professor of Wildland Fire Science & Director, Master of Natural Resources at the University of Idaho. 

The Our Gem Coeur d’Alene Lake Collaborative is a team of committed and passionate professionals working to preserve lake health and protect water quality by promoting community awareness of local water resources through education, outreach, and stewardship. Our Gem includes local experts from the University of Idaho - Idaho Water Resources Research Institute, Coeur d’Alene Tribe, Idaho Department of Environmental Quality, the Basin Environmental Improvement Project Commission, Kootenai Environmental Alliance.