How to Find Out Where Dangerous Blue Algae Is in Montana’s Waters

In the summers in Montana, it’s common to cool off in the state’s various beautiful watering holes like the Clark Fork River and Salmon Lake. When temperatures rise though, you might not be swimming alone in the water.

Blue-green algae

Harmful algae can form in Montana’s lakes and rivers when it gets hot, and the waters are rich with nutrients. When the algae reproduce quickly, a “bloom” occurs.

Algal blooms can have negative impacts on wildlife and other aquatic plant life, but they can be a major risk to recreators—and their pets—as well. While not all algae are bad, blue-green algae can be toxic to children and pets when it’s ingested.

Luckily, the Montana Department of Environmental Quality has an interactive map online that shows where blue-green algae have reportedly been found. Not all reports are confirmed by water testing and the map might not be inclusive of all blooms.

If you believe you may have spotted a harmful algal bloom, let the other water lovers of Montana know! You can report algae on the Montana DEQ’s website.

What to do if you swim in blooming water

Signs there may be an algal bloom in the water are often visible. Water may look green and soupy, or sometimes as though paint was spilled on top of it, when harmful algae is growing. The water can also smell swampy when algae are around.

The Montana Department of Public Health and Human Services advises people to stay out of water if there is a suspected algal bloom present.

However, if you think you might have swam through an algal bloom, you should rinse with fresh water as soon as possible. This goes for your furry friends, too! Pets can still get sick from licking water off their fur if an algae bloom was present.

If you think you may have swallowed water with blue-green algae, you should call poison control (or your veterinarian, if your dog did).

According to the map, the only area around Missoula right now that has a report of a potentially harmful bloom is at Hayden Lake.

Before you head out to make a splash, be sure to check the algae map! And if you’re ever in doubt about the safety of the water, just stay out.