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Keeping you and your pets safe from harmful lake algae

Posted at 11:40 AM, Aug 22, 2019
and last updated 2019-08-22 12:40:55-04

Any lake-lover knows blue-green algae as the slimy stuff that sits on the surface of the water and makes your cringe when you accidentally swim into a patch, but when in bloom, the algae can produce toxins that are harmful to humans and animals.

Blue-green algae is a natural part of large bodies of water, but can become harmful when exposed to larger amounts of sunlight and nutrients - usually in the summer months, according to the Wisconsin Department of Health Services. Some side effects of blue-green algae are vomiting, diarrhea, blistering, sore throat and cough.

In order to avoid the algae, watch out for water that looks like spilled latex paint, green pea soup, is discolored or streaky, has small green dots floating in it, floating scum, globs or mats or has dead fish of other animals floating in it.

If you're not sure whether or not the water is safe to swim in there are two ways to test it. The first way is to collect a water sample in a jar, scrape off the top layer of scum, shake up the jar and let it sit for about two to three hours. Then, look to see where the algae has settled. If it sinks to the bottom it is likely to be safe, true algae. If it forms a greenish ring at the top of the water, it is likely to be blue green-algae.

The second, and easier, way to check for harmful blue-green algae is the stick test. For this test, grab a long, sturdy stick and collect algae from the surface of the water. If the stick comes out of the water looking like it has been dipped in a can of paint, the material is likely blue-green algae. If it comes out with long, green, hair-like strands or threads, it is most likely true algae.

If you or your pet do come into contact with an algae bloom make sure to immediately shower off with fresh, clean water.

Seek medical/veterinary care if you or your pet acquire symptoms of blue green algae, or call the Wisconsin Poison Center at 800-222-1222.

You can report blue-green algae blooms to the Wisconsin Department of Natural Resources at