Photo by Linda HeronPhoto Credit


Algae blooms are becoming a common problem in many of our lakes and rivers.  Climate change, warming water temperatures, low water levels and flow, eutrophication, phosphorus from fertilizers, soaps, and detergents; and pollution from untreated, undertreated and treated effluent from waste water treatment facilities into our watersheds, all contribute to its increasing growth and prevalence.


A natural and common form of algae is called Cladophora, and you can often smell it before you see it because it floats into shorelines and begins to decay and rot.

Cladophora are green algae that thrive on phosphorus and other nutrients in the lake or river water. This form of algae reaches peak growth from May to July, on the bottom along the shorelines and shallow water.

When the water temperature rises, the algae begin to die and loosen from the bottom. Strong winds and waves detach large quantities that become floating masses that can lodge on shore and begin to decay. The decaying algae cause the unpleasant odour.

Cladophora is not harmful to your health, althought the decaying algae can cause a very unpleasant odour and can form large floating deposits along our shorelines.   The rotting algae also adds to the nutrient levels in the lake, which only perpetuates the cycle.


Cyanobacteria, or “blue-green algae” as it’s commonly known, are relatively simple, primitive life forms closely related to bacteria.  Cyanobacteria are found throughout the world in terrestrial, freshwater and marine habitats, but blooms typically occur in freshwater.

There are several species of Cyanobacteria – some are toxic and others are not.  Once it starts to decay it has a very bad smell, like rotting garbage.  That is when it is at its most dangerous because it releases the toxins.   Some of the toxins can attack the liver, nervous system and irritate the skin.

Boiling water does not get rid of the toxins, it only encourages the release of more toxins.

Check out this excellent article appearing in The Sudbury Star Green Poison: Toxic Blooms Plague Lake on 8 November 2008.


What You Can Do

Residents can help reduce the problem by reducing the amount of nutrients going into our watershed:

  • Avoid washing your car in the driveway – the soap will run into the storm sewer and from there into the watershed
  • Avoid fertilizing your lawn – rain and watering will carry fertilizers into storm sewers and out into the watershed
  • Stoop and Scoop – pick up after your pets
  • Use phosphate free soaps and detergents
  • Only use fertilizer when absolutely necessary, and if you do use it, use a phosphorus free variety – 10-0-10