- Didymosphenia geminata — nicknamed ‘didymo’ or ‘rock snot’ — is an algae that forms thick mats
- Since 2015, it has been found in at least six rivers in Michigan
- The nonprofit Michigan Trout Unlimited is looking for residents to collect water samples to test more locations for the algae
A Michigan nonprofit is looking for residents to help test for a potentially problematic matting algae.
Didymosphenia geminata — nicknamed “didymo” or “rock snot” — has already been found in at least six rivers in Michigan, but researchers want to get a better sense of how widespread it is.
The algae latches onto hard surfaces like rocks and forms beige-colored mats that resemble wet wool. When spotted in a river, people sometimes mistake it for sewage overflow.
“Because that’s kind of what it looks like is like wet toilet paper,” Ashley Moerke, dean of the College of Great Lakes Ecology and Education and executive director of the Center for Freshwater Research and Education at Lake Superior State University said during a recent webinar.
The algae, like trout, prefers coldwater streams where rocks typically provide important habitat for aquatic insects, river plants and fish eggs. When rock snot is present, it blankets rocks, blocking out light and disrupting those important nooks and crannies.
Didymo is native to northern Europe and parts of North America, but it wasn’t officially reported in Michigan until 2015, when it was found in the St. Marys River in the Upper Peninsula. The algae has since been confirmed in five Lower Peninsula rivers: the Manistee, the Boardman, the Au Sable, the Rapid and the Jordan.
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Last year, Michigan Trout Unlimited — in partnership with the Michigan Department of Environment, Great Lakes and Energy; the Michigan Department of Natural Resources; Great Lakes Environmental Center and the nationalTrout Unlimited group — trained volunteers to take river samples wherever was convenient for them and then tested those samples for didymo.
Using those results, Michigan Trout Unlimited put together a map that shows where the samples were taken and which samples came back positive for didymo.
This year, the nonprofit, with help from its partners, is asking for residents to do targeted testing.
“We’re now gonna move into filling in a very specific way, making requests and ensuring that very specific sites where we have gaps in the map are filled throughout this spring and summer, so that we can have a complete picture,” Bryan Burroughs, executive director of Michigan Trout Unlimited, said in the webinar.
People who are interested in collecting water samples for testing can contact Michigan Trout Unlimited through its website.
“And we’ll coordinate with you and figure out how many sample kits you need and ask you where you want to sample,” Burroughs said. “We might ask you if you’re willing to sample some other locations nearby.”
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Michigan Trout Unlimited has also been doing ongoing testing of three river sites — one on the Boardman, one on the Manistee and one on the Au Sable — to try to understand what may cause rock snot to not only be present but escalate to a bloom. Other researchers, like Moerke’s team at Lake Superior State University, have also been trying to find patterns in the St. Marys River to help determine what causes rock snot to bloom.
Didymo is thought to be transferred to new locations via boats, fishing gear, boots and inner tubes. Michigan recommends using a chemical disinfectant like Formula 409 to try to decontaminate gear and equipment before taking it to a new location.
More information on rock snot can be found here.
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