By now, everyone knows that Lake Clear has had its first AIS (aquatic invasive species) invasion. We have all seen zebra mussels under rocks in the water and on our docks and boat lifts. Unfortunately, Lake Clear’s natural water chemistry is very friendly to zebra mussels and they will now continue to multiply exponentially. During its 4 to 5-year (average) lifetime, a single zebra mussel will produce about five million eggs, and about 50,000 of these will reach adulthood. The offspring of a single mussel can in turn produce a total of half a billion adult offspring.

Zebra mussels eat small organisms called plankton (which includes algae) which drift in the water. In so doing, an adult zebra mussel can “filter” up to 1.5 litres of water a day, resulting in very clear looking water. That is why some people consider zebra mussels a mixed blessing – they’re hard on the feet, adversely affect the fish populations, clog boat and water intakes, but hey! The water will be clear!


Unfortunately, this upside has a huge downside. Zebra mussels live in near-shore areas, where they spit out phosphorous in a dissolved form that they have removed from ingested plankton, thereby concentrating phosphorous by our shorelines1. With the huge zebra mussel-producing factory mentioned above, we have one heck of a phosphorous delivery team. Add to that the runoff from septic systems, fertilizers, and other human activities, and you’ve got a phosphorous double whammy. So, while the middle of the lake is looking lovely and clear, near-shore areas become prone to algae blooms, both the slimy green kind, which grow throughout the summer, and the toxic blue-green kind, which bloom in the fall. Ingestion of blue-green algae can make you very sick, and can even be fatal, especially to pets that swim in and drink water from the lake.

1 This information is based on the studies of Dr. Conrad Grégoire. Dr Grégoire holds a PhD in chemistry and was the head of the Analytical Chemistry Research Laboratories at the Geological Survey of Canada.


The best way to prevent an algae bloom in front of your cottage is to avoid adding additional nutrients to the lake. First and foremost, a natural shoreline and buffer zone between the lake and your cottage will absorb a great deal of phosphorous before it can get to the lake. Native
trees and shrubs should be allowed to thrive. Bonus: This type of landscape is both beautiful and labour-free. No grass to cut, no flower beds to weed. If you simply stop cutting the grass and let nature take its course, you will find that native plants and trees will start to grow on
their own. If you are inclined to plant some trees and shrubs, so much the better. If you were around when Watersheds Canada issued every property owner an individualized Love Your Lake report, dig it out and have a look at the recommendations. In addition to planting (and forgive us if we state the obvious), have your septic system inspected every few years and pumped as needed, always use phosphate free soap, and avoid the use of fertilizer on your lot. If, for some reason, you do not have a septic system, ensure that human waste and grey water do not reach the lake by placing, for example, your outhouse, or you guests’ RV, as far back from the lake as your lot will allow.

If you would like more information, visit and download the Shoreline Habitat Creation Manual. Or use the link below to access “A Shoreline Owner’s Guide to Healthy Waterfronts” on the website of the Federation of Ontario Cottagers’
Associations (FOCA).

The LCC welcomes your feedback and your questions. You can reach us at Thank you for reading!