The Health of Lake Simcoe Update

The Health of Lake Simcoe is a concern for everyone lucky enough to live within its beautiful watershed. Lake Simcoe provides clean water to 7 municipalities, has a deep connection with the Indigenous community, and of course, is the perfect place for summer and winter activities alike. To ensure that we can continue enjoying Lake Simcoe, it’s important to know what the status of the lake is right now, to better adapt how we can sustainably interact with the lake.

         There are currently a few pollutants that are negatively impacting Lake Simcoe with varying effects on the water and ecosystem. Phosphorus is perhaps the greatest threat to the lake in the present day. Phosphorus can come from soil, sewage, and fertilizers that all enter the watershed and eventually reach Lake Simcoe. Like most naturally occurring elements phosphorus at a moderate level can be healthy, but an excess can be very harmful. A high phosphorus load increases algae and weed growth which contributes to lower oxygen levels. Low oxygen levels can kill ecosystems by making it impossible for life to sustain itself, destroying the ecosystem. The most recent update from the Lake Simcoe Region Conservation Authority shows that despite 2020 being our lowest phosphorus load in 20 years we are still 14 tonnes off our 44 tonnes per year goal. Since the year 2000 Lake Simcoe’s average phosphorus load has been 83 tonnes per year which on a positive note is lower than the 80s and 90s which saw an average of well over 100 tonnes per year. Although a significant amount of the phosphorus load is the result of soil from development projects it’s important to know that there are steps you can take in your everyday life to reduce Lake Simcoe’s phosphorus load. You can eliminate the use of fertilizers, use phosphate-free cleaners, and control soil erosion on your property.

         Salt is another pollutant that can have a very negative impact on the ecosystem. Too much salt can disrupt our freshwater ecosystem and also have a toxic impact on the lake for humans. Fish maintain a salt and water balance in their bodies by a process called “osmoregulation” which moves water into or out of their cells. Freshwater fish that are found in Lake Simcoe simply can’t adapt to the increase of salt in such a short period.  At our current salt pollution rate Lake Simcoe will reach toxic levels in as soon as 36 years. In addition, models indicate that 64% of plants and animals in Lake Simcoe may already be affected by salt contamination. It’s important to keep in mind during the wintertime that reducing your salt use can have an important role in changing our current pollution trajectory as residential salt is a key contributor.

         Another key indicator of lake health is the status of fish health. The measure of lake trout gives us key insight into the water quality and health of Lake Simcoe.  The Minister’s ten-year report of Lake Simcoe indicates a significant decrease in nearly every species of fish studied. Unfortunately, the Minister’s report offers no explanation or management plan for the decline in the Lake Simcoe fish ecosystem. Keeping our watershed free from pollution is the best way to protect our fish population.

         Hopefully, this blog has provided you with a deeper understanding of the current status of Lake Simcoe’s health. It’s important to remember that you have an impact on the watershed with your everyday actions. Avoiding the use of harmful pollutants on your property will help make sure Lake Simcoe can stay healthy for decades to come. Remember that the watershed is a delicate balancing act. Streams and creeks flow into Lake Simcoe, it’s our job to make sure all aspects stay healthy for Lake Simcoe’s well-being both now and in the future.  


Written by Tynan Webb, a Canada Summer Jobs student, funded by the Government of Canada and the Rescue Lake Simcoe Coalition. Original sources and references can be found here in the RLSC’s 2023 Lake Simcoe Update presentation: 

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