Why Are Some Lakes Green and Slimy?

Lake Erie is a water source for about 12 million people. The images show the lake at two different times.

stop and discuss

Look closely at the two images. What differences do you notice? What caused the differences?

Where is this?

Western Lake Erie during an algal bloom in 2014. The water became so toxic that a half million people around Toledo, Ohio could not drink or even have contact with their tap water.

Where is this?

Western Lake Erie when the ecosystem was balanced and healthy.

What makes an ecosystem become unbalanced and unhealthy?