How the Canadian Forest Fires Affect Lakes


The Canadian forest fires still rage on—an ominous start to fire season, for sure.  Smoke from forest fires contains various chemical compounds, including carbon, nitrogen, and phosphorus which are present in organic matter, such as vegetation and soil, which are burned during the fire.  These chemical compounds are nutrients that can negatively affect the health of a lake, pond or stream.


Carbon: Smoke and ash contains various carbon compounds. When these compounds are deposited in water bodies, they can contribute to increased dissolved carbon concentrations which can affect the water’s pH and alter the availability of certain nutrients. Additionally, carbon can influence the growth and productivity of aquatic organisms particularly algae and cyanobacteria. 


Nitrogen: Wildfire smoke can release nitrogen compounds, such as nitrogen dioxide (NO2) and nitrogen monoxide (NO), which can eventually dissolve in rainwater and be deposited in water bodies. Nitrogen is a nutrient that promotes the growth of aquatic plants and algae, and excessive nitrogen input, can lead to eutrophication, which is the excessive growth of algae and subsequent oxygen depletion in the water.


Phosphorus is present in organic matter and soil, and it can be released into the air as smoke during wildfires. When the smoke settles on land or water, it can contribute phosphorus to ecosystems. Phosphorus is an essential nutrient for plant growth, and in water bodies, it can stimulate algal blooms. Excessive phosphorus input can also lead to water quality issues and eutrophication with decreased oxygen levels and reduced biodiversity.


It’s important to note that the specific effects of wildfire smoke on nutrient inflows depend on various factors, including the intensity and duration of the fire, the proximity of water bodies to the fire, and the composition of the burned vegetation and soil. Additionally, local environmental conditions and existing nutrient levels in the water can influence the overall impact.  

Forest fires

Forest fires and the ash and smoke they produce can affect watersheds across wide geographic areas and time.

  • Rainwater in the burnt-out forest area washing the nutrients into nearby creeks, lakes and rivers (a local effect)
  • The ash and nutrients can be carried through watersheds great distances and transmit these effects downstream. In transit, the nutrients can be taken up to produce algae. This algae eventually dies off, decomposes and recycles the nutrients repeatedly.  This means that the nutrients can have an impact for many years over a large area.
  • Smoke can settle out naturally or be washed out of the atmosphere by rain and deposited thousands of miles from the fires.

The risk is that these additional nutrient inflows to our natural water infrastructure accelerate eutrophication which leads to algae blooms and eventually toxic cyanobacteria HABs.

If you are seeing a spike in algae in your waterbody following these fires and the blanketing smoke, visit our website at or give us a call at 610-431-1934, to discuss a custom treatment plan to help re-gain a healthy eco-system.