Why Not Go Swim in the Lakes

The results of wading only, but this guy still needs a rinse to be safe.
The results of wading only, but this guy still needs a rinse to be safe.

We are moving into the third week of May here in southern Wisconsin and have finally had a day or two near 80 degrees. Yesterday was a warm humid, day, the kind that makes a person think about taking a swim. I live in a city with four lakes, so a fresh water swim is never far away.

We humans have many options for keeping cool in warm weather; short and short-sleeved clothing, for instance. Dogs, on the other hand, have fewer options for cooling off.  Whether dogs shed or is trimmed, they still sport a lot of fur/hair and suffer when temperatures rise. Again, thoughts turn to swimming.

In our city of lakes, when the dogs and I are walking, water is never far away. However, we generally stay out of the lakes, no matter how warm it is. We know that these lakes sometimes contain blue-green algae.

About Blue-Green Algae
Blue-green algae, also known as Cyanobacteria spp. exist around the world and are found in the fossil record, according to the Centers for Disease Control on an informational page about this organism. Fresh water, brackish water and salt water all can host cyanobacteria.

There are a number of these photosynthetic bacterial species. Several of the species found in Wisconsin include Anabaena sp., Aphanizomenon sp., Microcystis sp., and Planktothrix sp., according to the Wisconsin Department of Natural Resources (DNR). And there are others.

As is the case with most bacteria, the individual algae are too small to see. However, they form colonies and eventually algal mats that float on the surface and along shorelines.
During certain weather and water conditions, these algal colonies become massive, with a slimy or foamy appearance (this Wisconsin DNR link shows a video of blue-green algae). These massive formations become algal blooms.

Conditions that stimulate blooms include very hot weather, still or windless days where the water as well as the air is calm, and frequent organic runoff, such as rainwater carrying farm waste or lawn fertilizers from yards.

The Problem with Blue-Green Algae
While green or true algae are an important part of the food chain in bodies of water, blue-green algae are not; they do not support aquatic life in bodies of water, according to the WI DNR. And as blooms of these cyanobacteria form and die off, they deplete lake water of oxygen, cause noticeable odor and taste issues, and produce a potentially fatal toxin. Specifically, microcystin toxin.

An article in The Scientist recently, tells the story of a Montana dog that nearly died from ingestion of microcystin toxin, after swimming in a lake that was contaminated with blue-green algae. The case and successful treatment of the dog led to a publication in the journal Toxins  on a successful new therapy for microcystin ingestion, via the use of cholestyramine.

This is exciting news, that there may be an antidote or therapy to save dogs from microcystin ingestion. Because it seems that blue-green algae problems are on the rise, here in  Wisconsin and elsewhere. The Scientist article noted that
“There is widespread agreement within the scientific community that the incidence of cyanobacterial harmful algal blooms (HABS) is increasing both in the U.S. and worldwide”,

citing an email from an Environmental Protection Agency (EPA) spokesperson. Here in southern Wisconsin the lakes used to remain relatively blue-green algae free until the dog days of summer, later in July and August. However, the algal smell and mats have appeared earlier the past several summers. And it goes without saying: These toxins, even with a potential antidote, are dangerous. We know they can affect humans as well as dogs.

What to Do
A good practice for any creature that swims in natural waters, other than streams and rivers, is a post-swim shower (shampoo possibly even better) to carefully remove any algal remnants.  In my case, if there is any question of water conditions or quality, the dogs and I don’t go in.

If you have additional ideas for protecting your dogs and yourself from blue-green algae, please let us know. We need to work on preventing blue-green algae in our waters, but while we do so, keep yourself and your pets safe.


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Kari Kenefick

Kari Kenefick

Kari has been a science writer/editor for Promega since 1996. Prior to that she enjoyed working in veterinary microbiology/immunology, and has an M.S. in Bacteriology, U of WI-Madison. Favorite topics include infectious disease, inflammation, aging, exercise, nutrition and personality traits. When not writing, she enjoys training her dogs in agility and obedience. About the practice of writing, as we say for cell-based assays, "add-mix-measure".

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