Kawartha Cottage Resources

Algae, the Kawarthas, and You

What are algae?


Algae are a large and diverse group of simple, photosynthetic organisms. They play a vital role in lake ecosystems as the start of the food chain. Algae are that essential link that takes the energy of sunlight and turns it into a form of energy that can be utilized by other organisms. Lakes support living things because of algae. Keeping a healthy and diverse community of algae in your lake is essential to good water quality.

Algae require several things to flourish: moisture, sunlight, nitrogen, phosphorus and other trace nutrients. Any nutrients not available in adequate supply will limit algae production. Or if available in excess, algal blooms of particular species may threaten water quality.

Do your part


Following these guidelines helps maintain a healthy algal community


Water quality is largely the result of human activity, both along the shore lines as well as throughout the watershed. Better water quality is found in less disturbed areas. The best way to maintain good water quality is to leave your property as natural as possible. There are several things you can do at your cottage:


  • Vegetate shorelines with native plants

  • Switch to phosphate-free detergents and soaps

  • Maintain your septic system to prevent nutrients and E. coli from entering the lake

  • Pick up animal waste

  • Refrain from chemical lawn treatments

  • Leave the grass several inches tall to absorb runoff



Algae as water quality indicators


Algae are very sensitive to environmental change, which makes them essential to the earliest possible detection of changes in water quality. Algal samples tell us about water conditions over time, whereas a water sample gives a mere snapshot of water conditions at the time of sampling. Looking at changes in algal communities will allow us to address issues before they become large-scale problems in our lakes.

Remember, algae are an important part of the food web. Without algae, there would be no fish. A healthy algal community usually has low to moderate growth and lots of diversity. Reducing your impact on the watershed is the best way to ensure a healthy lake.

Remember, algae are an essential part of your lake’s ecosystem. Without algae, there would be no life in your lake.

Is this bloom harmful?


There are hundreds of kinds of algae in fresh water. Only a handful is potentially harmful. Most harmful algae must be extremely abundant to be detrimental and fish kills are the most common result.

Microcystis, a common blue-green algae (cyanobacteria) is the most likely kind of harmful bloom in the Kawarthas. It presents as a blue-green cloud, floating on the surface of the water and may wash up on shores.

Microcystis produces a toxin which can cause illness to humans and animals when found at high concentrations. Filtering or boiling water will not remove the toxins. Use of lake water should be avoided until the bloom has passed.

Should you see an algae bloom you suspect may be microcystis contact The Spills Action Centre at 1-800-268-6060 or your Ministry of the Environment local district office.

The oldest task in human history: to live on a piece of land without spoiling it.
Aldo Leopold

Photo courtesy of Alex Quinn - Creative Commons