Where does that green slime come from in the Fox River?

Kirsten Klahn
Green slime builds up on the Fox River this summer in Waukesha.
Published on: 7/8/2014

Do you wonder why the green slime that pools together on the Fox River becomes more noticeable throughout the summer months? Ever wondered what it is and where it comes from?

The green slime is algae blooms, said Heidi Bunk, a water resources management specialist for the Wisconsin Department of Natural Resources.

Here's how it works: When it rains, phosphorous, which comes from things such as construction projects, manure runoff and roads, streams into the water and settles. After enough phosphorous has entered the water and has sat there for quite some time, the algae blooms begin to form, Bunk said.

When the algae blooms are faced with hot temperatures and stagnant water, the organisms thrive and multiply, coating the water with the green foam. After particularly hot days with little wind, the algae blooms become even more noticeable, Bunk said.

"This isn't caused by just one event," Bunk said. "This is caused by a series of events over time."