TRAVERSE CITY, Mich. (Michigan News Source) – The Great Lakes Environmental Center has verified that there is didymo in a stretch of the Boardman River in Blair Township in Grand Traverse County in Northern Lower Michigan. Didymo is an invasive algae that’s also known as “rock snot” which resembles wet woll.
This algae produces nuisance growths in freshwater rivers and streams with consistently cold water temperatures and low nutrient levels.
The Michigan Department of Natural Resources (DNR) states, “Didymo mats can cover stream beds and reduce habitat for macro invertebrates including mayfly and caddisfly nymphs, which are important food for fish.” According to iNaturalist, a joint initiative of the California Academy of Sciences and the National Geographic Society, the distribution of rock snot in the last two decades appears to be gradually expanding both outside and inside of it’s native range of northern North America and Europe.
According to the Traverse City Ticker, Sarah LeSage, aquatic invasive species program coordinator with the Michigan Department of Environment, Great Lakes and Energy (EGLE) is not sure how the rock snot got into the Boardman River. She said, “Researchers aren’t yet clear on whether didymo appears because it’s been transported into the river – such as on boats or waders or fishing equipment – or if it’s already present in low numbers and then suddenly blooms due to environmental changes, developing long stalks that make previously undetected algae cells visible on hand surfaces in the streambed.”
This algae was also found in the Upper Manistee River in Kalkaska County in December of 2021 and has been found in the St. Marys River in the Upper Peninsula since 2015.
Rock Snot is not considered a significant human health risk but it affects stream habitats and sources of food for fish. It also makes recreational activities unpleasant and it’s not something that’s easy to deal with once you leave the river.
For now, state officials are putting up signs along the Boardman River asking users to “clean, drain and dry” after being on the river, which can stop the spread of other aquatic invasive species as well.
They would like people to clean/remove mud and debris from all surfaces, drain water from all bilges, wells and tanks and drying equipment for at least five days or disinfect it with hot water or a diluted bleach solution. This applies to recreational equipment like tubes and kayaks as well as boating and fishing gear. Michiganders are asked to report any observances of rock snot that they see to the Midwest Invasive Species Information Network.
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Besides the impact on insect levels and fish, the rock snot has an obvious negative aesthetic impact and is slippery as well, making the waters dangerous for swimmers and waders.
Any tools used to target the removal of didymo would be destructive to other native plants, animals and the habitat so the response to the algae so far has been to try to mitigate the spread.
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