The Science of Harmful Algal Blooms

Blue-green algae can create toxins that are harmful to humans and animals. Water should be avoided if:

• It looks like spilled paint
• Surface scums, mats or films are present
• It is discolored or has colored streaks
• There are green globs floating below the surface.

Caption informed by: ohioalgaeinfo.com

The colors we see in this aerial image may seem beautiful, but sometimes color contrasts like this can mean unhealthy bodies of water.

Notice the deep blue areas toward the center of the lake vs. the green-blue areas around the edges of the lake. The center of the lake is deeper, and therefore has generally cooler waters. The outer edges of the lake are more shallow and warmer – which we know is a great environment for the formation of algal blooms.

Identify Lake Erie on the map of the Great Lakes. Notice the contrast in color and clarity. You can see that many of the lakes have clear waters. When we look at Lake Erie in this aerial photo, we can clearly see the green color caused by algal blooms.

Bathymetry is the measurement of depth of water in oceans, seas, or lakes. The bathymetric image shown here depicts the depths of Lake Erie. Notice where the lake is most shallow. As we look at aerial images of the lake, keep in mind where these shallow areas are, and where algal blooms most often appear.