Nutrients in the lake fertilize algae. Too much algae can turn the water green.
- Nutrients are needed for plants to grow on land and in the water.
- Two main nutrients are phosphorus and nitrogen.
- In freshwater lakes, phosphorus and nitrogen promote the growth of algae, microscopic floating plants (phytoplankton), and rooted aquatic plants.
- Nutrients along with sediments cause lakes to age.
- The natural aging process (eutrophication) can take centuries.
- BUT, human activities have accelerated changes in Torch Lake over just a few decades.
Did you know?
Nutrients, plant growth and water clarity determine the age of a lake. There are 3 age classes for lakes:
- Young lakes (oligotrophic) have low level of nutrients and a low level of plant growth with high water clarity. Torch Lake is an oligotrophic lake.
- Middle-age lakes (mesotrophic) have an intermediate level of nutrients and an intermediate level of plant growth. The water is often clear with submerged aquatic plants. Lake Bellaire is an example of a mesotrophic lake.
- Old lakes (eutrophic) have high levels of nutrients and high levels of plant growth. In a eutrophic lake, if algae dominate, the water clarity will be poor. But if aquatic plants dominate, the water will be clear. Clam Lake is a eutrophic lake.
As lakes age, they gradually become filled with sediments and become a wet meadow or dry lake.
This process can take centuries.
- Human activities such as constructing buildings, paving roads and driveways with impermeable surfaces, filling wetlands and removing natural buffers along streams and the lake have increased the amount of nutrients in stormwater.
- Additional nutrient loading from lawn fertilizers, leaking septic systems and animal waste have speeded up this aging process, too.
Human Impact on Eutrophication
Nutrients act as fertilizers. Just as fertilizers turn lawns green, the nutrients in the fertilizers cause algae to grow in lakes. Then the lakes turn green. Algae can grow in small patches or massive algal blooms that spread along the shore and out into the lake. Algal blooms generally occur where there are high levels of nutrients coupled with warm, sunny and calm conditions. Some algal blooms are toxic killing fish and harming humans.
Algal bloom – Sleeping Bear Dunes National Lakeshore (August 6, 2012)
Algae (Cladaphora) on rocks in Torch Lake
We know you want to enjoy the lake for many years (and generations) to come. So, we’ve put together a list of simple steps you can take to reduce the nutrients, sediments and toxins flowing into the lake and its streams.