Nutrients, Sprays & Chemical Applicants

An Interconnected System


Your lake is part of a larger interconnected water system called a watershed. This watershed is an area of land that contains a common set of small streams, rivers, wetlands, and lakes, that all drain into a larger receiving water body, which is typically a larger lake. Because of this interconnectedness between land and water, what we do on the land can have drastic effects on the health and integrity of our water.

There are a number of land-based activities that can impact our water, but two of the most drastic involve the use of chemical sprays and applicants as well as nutrients, both of which can run off into the water. It is important to note that maintaining lake health is a combined effort from all the inhabitants of a watershed, especially those who live along the water’s edge!


Nutrients are things we apply on land (typically as fertilizers) to support the growth of plants. They include things like phosphorus, calcium, and nitrogen. Because this is generally seen as a positive thing, it can be hard to see the problem as it pertains to water health at first. However, nutrient runoff can have a drastic impact on our lakes. This is because when nutrient levels in the water rise beyond their natural levels, it can promote the growth of algae. This algal growth then becomes a substantial drain on available oxygen in the water. In drastic cases, algal growth becomes so exacerbated that it effectively "chokes" the lake of oxygen, creating something called an "algal bloom". Those who have lived on our near a lake with an algal bloom know how unpleasant it can be and if severe enough, algal blooms can become a substantial threat to human health. In addition to fertilizers, some other potential sources of nutrients include:

  • Unmaintained or leaky septic tanks
  • The application of road salt
  • The discharge of household cleaning supplies, soaps and laundry detergents
  • The removal of both standing and dead trees, leaf litter or decaying and rocky  material on the forest floor
  • Leaching and runoff of human, pet and livestock waste
  • Increased runoff from upland areas due to hardened surfaces like buildings, driveways, lawns and patios, and/or from the removal of native vegetation along the shoreland
  • Increased soil erosion due to shoreland development and irrigation systems
  • Climate change which results in more frequent and intense storms on average, thus resulting in more water hitting the ground and increased runoff of nutrients from septics, manure, fertilizers, etc.

Chemical Sprays & Applicants

Mosquito sprays, whether touted as natural or not, have incredibly harmful effects on biodiversity within a lake ecosystem. Mosquitoes are attracted to LED lights and open spaces where natural predators such as dragonflies and songbirds are lacking. All mosquito sprays, including natural types, contain nerve tonics that can harm pregnant women, but which are also broad spectrum and remove key pollinators as well as food for songbirds, fish, and amphibians. Declines in songbirds have reached 75% amongst some species in the last 20 years, many of which relate directly to mosquito sprays and insecticides that are exacerbated by LED lights/night lights and native habitat destruction. Mosquito sprays also have the effect of leaching into lake ecosystems to harm zooplankton and other essential aquatic animals. Other chemical sprays and applicants like herbicides and other pesticides also remove the foundation of food webs or have other secondary impacts to wildlife.

Nutrients, Sprays & Chemical Applicants & The Blue Lakes Program

One of the Performance Areas that participants can set goals and actions under within the Blue Lakes Program surrounds reducing the impacts of nutrients and chemical sprays and applicants on their lake. Participants may elect to work under this Performance Area if they are experiencing algal blooms, if their lake is at a higher risk of algal blooms, or even if they want to use more natural products in their household. Example actions participants can take within the Nutrients, Sprays & Chemical Applicants Performance Area include:

  • Supporting septic system health with inspections every 2-3 years
  • Limiting road salt application in the winter
  • Limiting the application of mosquito and chemical sprays
  • Promoting the employment of alternative techniques or tools such as bug jackets, smoke, mosquito attractors, and screens

Additional Resources

The Blue Lakes Program has put together resources on how property owners can reduce runoff from nutrients and chemical sprays on their property. You can launch this guide below!

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