Kansas State University

Be Aware of Harmful Algal Mats in Waterbodies

Submitted by Abigail Crouse

Harmful algal monitoring aligns with the water recreation season, specifically from April 1 to Oct. 31. Warm temperatures can negatively impact local waterbodies with substances that can be harmful to health. While many are aware of green slime referred to as harmful algal blooms, or HABs, it's also important to be informed about harmful algal mats, or HAMs, which can also threaten the health of communities and the safety of waterbodies.

In partnership with the Kansas Department of Health and Environment, K-State’s Pollution Prevention Institute has developed resources to provide education about both HABs and HAMs for privately owned, nonagricultural waterbodies. This information is crucial for private waterbody owners, including those with ponds in homeowners associations, golf courses and campgrounds.

What are Harmful Algal Mats?
Harmful algal mats are composed of blue-green algae that attach to the bottom of a waterbody or other surfaces. This is also known as benthic cyanobacteria, as opposed to harmful algal blooms, which are planktonic cyanobacteria that grow in the water column. While HABs often cause the general water color to appear opaque with a green cast, water with HAMs may remain clear with no noticeable cast.

What do HAMs look like?
Harmful algal mats often appear as floating mats or "carpet" like structures. They are composed of filaments and are often brown or black in color. While HABs tend to occur more during warmer summer months and can change rapidly, HAMs can persist throughout the year, and more mats may float to the surface or wash up on shorelines during the summer.

To safeguard public health, individuals should be observant of water conditions. For HABs, be aware of discolored water, particularly shades of green, the presence of surface scum, with or without unpleasant odors. For HAMs, look for brown or black filamentous mats floating or attached to surfaces, with or without unpleasant odors. If any of these indicators are present, it is advisable to avoid contact with the water entirely! Look for posted signage that may warn of HABs or HAMs.

The K-State Pollution Prevention Institute has compiled a valuable "Who to Call?" list, providing essential contact information for water testing services, bloom reporting procedures and guidance on managing exposure to HABs. Additional resources and detailed information can be accessed through the K-State Pollution Prevention Institute’s HABs website.