How to Control Blue Green Algae

Blue green algae, so called because they are aquatic and photosynthetic, are actually colonies of single-celled bacteria called cyanobacteria. Though they are important to the nitrogen cycle, blooms can also be harmful to pets and humans. Controlling blue green algae blooms in recreational and drinking water is therefore desirable.

Difficulty: Moderate

Instructions

Things You'll Need:

• Water supply

The Steps

1. Know what factors affect growth and reproduction of cyanobacteria. Light, temperature, and nutrients are needed. Depending on the species, cyanobacteria can thrive in waters except where light is almost absent. Temperatures of 82 degrees Fahrenheit or higher promote steady growth. With the correct nutrients available, cyanobacteria can thrive until light or temperature become limiting factors.

2. Know what factors you can control. Though it may be difficult or impossible to change the availability of light or the temperature of a body of water, people can significantly impact the amount of available nutrients.

3. Reduce or eliminate use of lawn fertilizers except when absolutely needed. Choose phosphorus-free fertilizers when possible. The nutrients from these fertilizers can run off into storm drains and flow to lakes and rivers, providing the food source blue green algae require to bloom.

4. Eliminate household contributions to nutrient runoff by choosing phosphorus-free detergents. Also, fix leaking septic systems to prevent nutrient runoff from decomposing waste.

5. Bag and dispose of leaves and grass clippings to keep them from washing into storm drains, where they create nutrient runoff as they decompose.

6. Plant a buffer zone of native vegetation around bodies of water. Native vegetation have an increased ability to filter nutrient runoff and prevent it from entering bodies of water.

Tips & Warnings

• Contact your state health department for help dealing with algal blooms in private waters, or to report blooms in public waters.
• Never treat waters experiencing a bloom of cyanobacteria with algaecides. Cyanobacteria release dangerous toxins when they die.

References

• North American Lake Management Society
• Wisconsin Department of Natural Resources