August 22 – 28, 2025Vol. 27, No. 11

Do We Need to Worry About Gloeotrichia?

Gloeotrichia (pronounced “glee-oh-tricky-ah”) echinulata. — *Gloeotrichia* (pronounced “glee-oh-tricky-ah”) *echinulata*.

by Matt Farragher

If you have been out on Great Pond, Long Pond or Messalonskee Lake recently, you may have noticed small green particles drifting in the water or collecting along the shore. This is a type of cyanobacterium called gloeotrichia echinulata, which has been showing up in high numbers this summer.

“Gloeo” emerges in late-summer and can form dense scums or mats along shorelines, particularly in coves and downwind areas. Gloeo can accumulate near your shore one day and dissipate the next day, making gloeo a challenge to predict and monitor.

Often considered a nuisance algae, gloeo can cause skin irritation and rashes for some swimmers. As gloeo dies, it breaks down and has the potential to release toxic chemicals. Although we have not detected any toxins in our testing, caution is still warranted. The lake science team at 7 Lakes Alliance recommends avoiding contact with water where dense accumulations of gloeo are present. Children and dogs should be kept out of areas with dense accumulations to avoid ingesting water, and swimmers should take a shower with fresh or filtered water and soap after swimming in water with gloeo.

Why is This Happening?

Gloeo has been appearing more frequently and at higher abundance in recent years in otherwise clear, low-nutrient lakes across North America and Europe, including several of the Belgrade Lakes. Warming water temperatures has lead to earlier and more severe depletion of oxygen on the bottom of lakes, which triggers phosphorus to be released from lake sediments and into the water where it becomes available for algae. Phosphorus is the most important nutrient that initiates excess algae growth in our lakes. The gloeo spores develop in the bottom waters near sediment containing phosphorus, then float to the surface where they reproduce and are can be distributed horizontally by wind-driven water currents.

What Can We Do About Gloeo?

The Lake Science team at 7 Lakes Alliance has been monitoring gloeo progression regularly, and our volunteer monitors have been tracking abundances around the lakes as well. The solutions for the lakes start on the land. Erosion control is one of the most effective ways to reduce the amount of phosphorus entering our lakes. Actions such as:

Maintaining a natural shoreline buffer with native plants,
Conserving land and keeping tree cover to reduce runoff and cool the nearby land and water, and
Supporting erosion-control projects, both large and small. (7 Lakes Alliance works on both large-scale erosion control projects with towns, road associations, and smaller projects through our YCC program.)

There is still more to be done, and it requires community-wide effort. If you would like more information or would like to help monitor gloeo, please contact matt.farragher@7lakesalliance.org or danielle.wain@7lakesalliance.org.