Image: Nine Mile Creek Watershed District

Have you ever passed by a shallow lake or wetland and wondered what was growing out there in the water? Is it bad, or should we be worried? 

Shallow lakes are a hotbed of activity during the summer months. Unlike deep lakes that are common in northern Minnesota, shallow lakes and wetlands are heavily impacted by sunlight. Instead of maintaining cool depths like a deep lake, shallow lakes warm up from the lake bed to the surface. In addition, wind and wave action on a shallow lake can stir up more sediment, bringing more nutrients into the water column. This creates a favorable environment for plants and algae that specialize in warm water with plenty of nutrients up for grabs.

This summer, below average rainfall and warm temperatures have created favorable conditions for a variety of algae and other aquatic plant life. Some plants and algae may be mysterious and their names aren't always easy to pronounce. But with practice it can be easy to distinguish between average shallow freshwater conditions and causes for concern. 

Dense plant growth and some algae are natural features of shallow lakes, but excessive nutrients and algae can impair them. Visit our residents page for more on what you can do to help support the health of shallow lakes, wetlands, and streams. 

If you're wondering about a sighting, contact us via email with a photo and staff will be glad to provide assistance. 

Download a PDF of this graphic here.

For more info:

MPCA: Frequently Asked Questions About Lakes

DNR: Aquatic Plant Management