Lake Life Water Warrior
photo by Sue Pais
Clean vs. Clear Lakes by Dr. Nate Bosch, director of the Lilly Center for Lakes & Streams
If your lake is clear, that must mean it is clean… right? Well, from a scientific perspective, a clean lake does not have to be clear — and a clear lake is not always clean. 20
LAKElife Magazine July 2020
A clear lake is easy to spot. There are no visible particles in the water; it is not muddied by sediment or algae blooms. You can usually see fish swimming around at the bottom. But a clear lake might be hiding bacteria, pesticides or toxins, like the ones algae produces. The presence of algae is not always a good indicator of a lake’s cleanliness since small amounts of algae can produce large amounts of toxin. A clear lake might have more algae toxins than one stained brown. On the flipside, a safe lake can masquerade as an unsafe, dirty one. The water might be a murky shade of tan, with underwater life hidden by small amounts dirt and algae. Even though you might not be sure where to put your feet in a lake like this, it is probably not dangerous to swim or fish there. That brown color most often comes from natural tannins found in trees. Like a tea bag steeping in hot water, tannins seep from the roots of nearby trees, and stain the lake water a light brown. Although you should not drink this water, it is safe for swimming, fishing and boating.
Next time you jump off your dock or wade into the shallows at a public beach, remember that the water’s color does not always determine its cleanliness! One clear indication to avoid a lake is the presence of blue-green algae. This kind of algae tends to flourish in shallow water and high heat, and can produce a toxin that is harmful to people and pets. It takes many forms but will often look like blue-green paint spilled over the surface of the water. If you see what you think is a blue-green algae bloom, take a picture and send the Lilly Center an email (lakes@grace.edu) so we can help you identify the species. Rest assured that the Lilly Center is working hard to help preserve and protect your family by monitoring, studying and informing you about the presence of toxins in local lakes. Learn more about blue-green algae at lakes.grace.edu or call 574.372.5100, ext. 6445.
