Invasive algae known by some as "rock-snot" has been discovered for the first time in several northeastern Minnesota streams. 

Researchers with the Science Museum of Minnesota, the Minnesota Department of Natural Resources and the University of Wisconsin Oshkosh identified Didymosphenia geminata (often called Didymo or rock-snot) in the Caribou, Devil Track, Kadunce, Kimball and Onion rivers. 

This type of algae has never before been found in those rivers. 

A news release from the Science Museum of Minnesota says the algal blooms are not necessarily an indication of poor water quality, but they can create "significant problems when they cover natural stream habitats and turn in-stream nutrients into a difficult-to-digest food source for other organisms."

Scientists surveyed 24 streams from the Lester River in Duluth north to Grand Portage River, as well as Lake Superior shore sites, finding rock-snot in five rivers.

They plan to continue to examine the streams with algae over the next year using microscopy and DNA so they can determine if the algal blooms are affected by changing conditions, or if they are non-native and were introduced from other regions. 

“Until the origin of these new Didymo populations is known, we encourage those who enter streams to avoid river-hopping in a day,” David Burge of the Science Museum of Minnesota said in the release. “As is always our practice during field sampling, if you are going to enter streams, please adopt aquatic invasive species (AIS) decontamination practices. 

"And as tempting as it is to reduce slipping on slimy rocks, please refrain from the use of felt-soled boots; wet soles can harbor many AIS, including Didymo, for long periods of time," Burge added.

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Rock-snot has been reported as a "well-behaved" alga in Lake Superior for more than 60 years. But in 2018, the DNR found "cotton candy" growths of the invasive diatom in the Poplar River at Lutsen, marking a first on the North Shore.

“The DNR has been watching out for Didymo for years, and why it is forming nuisance mats is something of a mystery,” Minnesota Department of Natural Resources Fisheries Research Scientist Heidi Rantala said in the release. “We don’t know what the presence of Didymo means for the ecology, including the fish communities, of North Shore streams."

They are working to understand the impacts of this type of algae. Anyone who spots it is asked to report it online here

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