by Erica Clites, Extension Educator, Michigan Sea Grant

Algal blooms occur when tiny, naturally occurring plants grow rapidly in an area of water and are visible without a microscope. The lake water may look green (or other colors, like purple) or have scum floating on the top of it. Not all algal blooms are toxic but some are. Algal blooms capable of producing toxins dangerous to humans or animals are considered Harmful Algal Blooms (HABs). Reports of HABs have been increasing in Michigan since 2013 and include both inland lakes as well as the Great Lakes. An online map shows 2023 reports and confirmed inland lake blooms. Western Lake Erie and the Saginaw Bay, as well as Lake Superior, have also had confirmed HABs.

A Harmful Algal Bloom (HAB) in an inland lake. Photo: Todd Marsee/Michigan Sea Grant

How do you know if something is a HAB or not? A HAB looks like spilled paint or pea soup, and can have floating scums, mats, sheens, clumps or streaks. There are several natural phenomena like tiny aquatic plants, pollen or filamentous algae that may look similar but aren’t HABs.

Examples of other phenomena that can be confused for HABs (from left to right): tiny aquatic plants, pollen and filamentous algae. Aquatic plant photo by EGLE, other photos submitted by Michigan residents.

Harmful Algal Blooms can have a variety of health impacts for people including skin rashes, a runny nose or stomach pain and headaches. If you suspect that a harmful algal bloom is present, do not allow pets or livestock to drink or swim in the water. Pets tend to swallow more water than people and may take in more toxins becoming seriously ill or die.

Michigan Sea Grant and partners around the state hosted a HABs 101 webinar March 6. The full recording and list of resources are now available. Find out what harmful algal blooms look like, the role of algae in the ecosystem, information about how to respond if a potential HAB is observed and how to prevent and reduce the likelihood of a HAB occurrence. Listen in to bust some myths, get tips for keeping your family and pets safe, and learn how you can take action to support healthy water quality on your property and in your community.

Learn more at Erica’s session at our Annual Conference, scheduled on Saturday afternoon!

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