What is that green stuff in the lake?

By David Ernes – Lake Management Committee

If you recall, not all algae are bad. Green algae usually pose no significant concerns, other than their aesthetic appearance. On the other hand, blue-green algae have the potential to generate toxins that can be harmful. How does one decide if what they see is green algae or blue-green algae? Unfortunately, the only accurate method is to examine the organism under magnification and assess its structure by experts in this type of analysis.

In spite of this, there are some general features that can help to differentiate the types of algae. Most informational articles include a significant number of pictures showing visually what each type looks like. One good source showing both types can be found on a New York web site (www.dec.ny.gov/chemical/81962.html).

Generally, green algae often look like floating rafts, and may appear as if it were a bubbling scum on the surface of the water that may entangle with other plants. There is also a type of green algae that is stringy, or silky and coat rocks and other areas. Duckweed looks like small disks and tend to clump into areas.

Blue-green algae, on the other hand, can appear as green streaks, as spilled paint or pea soup. It can also form as small dots that disperse when disturbed. Others types may look like grass clippings. Blue-green algae are often accompanied by a foul odor (described in some articles as “pigpen” odor).

Other observations one may see in the lake are not algae at all. You may recall a previous article about bryozoans, which are a beneficial organism. You may also see what appears to be foam on the water. This is caused by decomposition products from algae and other plants which, due to wind or agitation, can cause the foam. It can even be seen as parallel streaks in the lake in the direction of the wind. This is harmless and a natural phenomenon in lakes.

Common sense tells us not to swim in any waters that contain unusual amounts of algae. It is best just to avoid contact to insure that you minimize any adverse effects. When in doubt, choose a different spot or visit one of our inviting pools. Please enjoy our beautiful lake and have a safe summer.

BE LAKE RESPONSIBLE