Guest Blog by Morgan Murphy, Canada Summer Jobs Student and a Conservation Biology student at Trent University
As many fishing fans know, Lake Simcoe is home to a variety of fish species that provide for an exciting and worthwhile day on the lake. From the common yet tasty yellow perch to the prized 15-pound trout and pike, our lake has a lot to offer. Whether it’s for family dinner or bragging rights, you can always rely on the Lake Simcoe fishing community to appreciate a good catch.
What many fishers don’t think about is the diet needed to bulk these swimmers up for the hook. Every organism in the lake is part of a food chain that is necessary to maintain balanced population levels. Even minor changes in the structure of this web can have cascading effects on every creature involved. While you may have already learned this in high school biology, what you should know now is that the integrity of this cycle is currently at risk in Lake Simcoe.
The Problem
Every winter in Ontario, road salt is used to manage snow and ice on streets, sidewalks, and parking lots. While this method is useful for preventing injuries related to slips, the amount of salt used every winter has become excessive. Over 90,000 tonnes of salt was estimated to have been applied in the Lake Simcoe watershed in the 2012-2013 winter season. An estimate from 2023 now says that the average is closer to 100,000 tonnes. The largest contributors are local road networks, meaning as urban development and sprawl increases, the road salt usage increases too.
Figure 1: Graph displaying the positive trend of chloride concentrations in Lake Simcoe. Based on the current rate of increase, chloride concentrations will exceed chronic exposure guidelines by 2120.
Source: https://lsrca.on.ca/index.php/2023/07/26/sodium-chloride/
When the snow melts, road salt runoff enters our watershed and has effects on both water quality and the health of aquatic species. Although the highest chloride levels are present in winter and early spring, the soluble nature of chloride makes it very difficult to extract once it has made its way into the water. This means that Lake Simcoe feels the effects of road salt year-round despite major applications only lasting 6 months.
The Victims of Road Salt
To understand the severity of the impacts our watershed ecosystems face, we must start by examining the effects that chloride has on Lake Simcoe’s smallest critters: zooplankton. These microscopic animals are at the bottom of the food chain alongside insect larvae and algae. Studies have shown that most species of plankton are sensitive to fluctuations in salt concentration, especially in freshwater environments where they haven’t been previously exposed. Changes in salt concentration can also affect algae abundance, which can cause increased zooplankton mortality and a decrease in viable plankton eggs.
While larger, vertebrate species have been shown to be more tolerant to changes in water salinity, they prey on less tolerant invertebrates. Zooplankton are a food source for most fish in Lake Simcoe at some point in their lives, meaning they depend on hearty and abundant plankton to fuel their growth. Less food means smaller and fewer fish. These smaller fish also have a harder time reproducing, which only further decreases the population size.
Not only is increased salinity in our watershed affecting aquatic food chains, it is also impacting life on land. Amphibian species in Lake Simcoe are experiencing abnormalities in their life cycle, including reduced weight, activity, and time to metamorphosis. Their mortality rates are also increasing, all as a result of excessive chloride ions in the water. Birds, snakes, and small mammals rely on amphibians as a food source and feel the same effects that fish do when their food supply runs low.
Vulnerable Areas
The Lake Simcoe Region Conservation Authority has identified salt vulnerable areas within the watershed in order to determine the environments that are most at risk. A salt vulnerable area is defined as a region in which a minimum of five aquatic species are impacted by salt application. Most large communities in the Lake Simcoe watershed have been identified as salt vulnerable, such as Aurora, Newmarket, Keswick, Bradford, Barrie, and Orillia.
Figure 2: Map of the Lake Simcoe watershed displaying salt vulnerable areas and the number of aquatic species impacted by chloride.
Source: https://rescuelakesimcoe.org/wp-content/uploads/2024/02/salt-vulnerable-areas-LSRCA.pdf
Despite the disheartening facts, there is still hope for our watershed and the susceptible species that call it home. The LSRCA says that even a 25% reduction in salt application to roads and parking lots can reduce the impact on 33% of species currently suffering from chloride. It is also expected that this action could allow areas of moderate impacts to be delisted as vulnerable.
If you’re one of many Lake Simcoe residents who takes pride in the diverse fauna of the watershed, help encourage change in our community by going to saltcoalition.ca and clicking the ‘Take Action’ tab. This two-minute task will help support a sustainable future in Ontario by motivating provincial action that will stop salt pollution in it’s tracks.
Sources:
https://wires.onlinelibrary.wiley.com/doi/full/10.1002/wat2.1629
https://www.ontario.ca/document/lake-simcoe-protection-plan/aquatic-life
https://lsrca.on.ca/index.php/watershed-health/salt
https://www.fishingsimcoe.com/fish-species/lake-herring-cisco
https://www.epa.gov/great-lakes-monitoring/great-lakes-biology-monitoring-program
https://pubs.acs.org/doi/10.1021/es5061534
https://www.snexplores.org/article/shrinking-fish
https://lsrca.on.ca/index.php/2023/07/26/sodium-chloride