TRAVERSE CITY, MI – A nuisance alga called “rock snot” cropped up in a cold-water river in Michigan’s Lower Peninsula for the second time in nine months.
Officials at the Michigan Department of Environment, Great Lakes, and Energy (EGLE) on Aug. 24. 2022, confirmed that didymo – scientific name didymosphenia geminate – established an infestation in a stretch of the Boardman River in Grand Traverse County’s Blair Township. Experts found the invasive species in the Upper Manistee River in Kalkaska County in December 2021.
Didymo has been established in the St. Marys River in the Upper Peninsula since 2015.
Sarah LeSage, EGLE aquatic invasive species program coordinator, said a photograph of suspected didymo alga was Aug. 17 posted online to a Michigan sportsman forum and then forwarded to the state Department of Natural Resources.
On Monday, Aug. 22, 2022, LeSage visited Shumsky’s Canoe Launch and a bridge access off East River Road in Blair Township near Traverse City to collect samples, which were verified the next day by the Great Lakes Environmental Center.
State officials and volunteers spread out to check a dozen rivers across northern Michigan in May after the discovery of didymo in the Manistee.
Multiple spots along the Boardman River were checked as part of that spring effort, including Shumsky’s launch. Didymo was not found in the Boardman nor any other rivers at that time.
In the few months since then, mats of the alga grew across the river bottom at the popular public access spot on the Boardman.
LeSage said there are not a lot of historical samples to show whether didymo may be present but undetected in other Michigan streams.
“It’s possible that environmental factors like changes in water chemistry or quality are causing it to ‘bloom’ or develop long stalks, making previously undetected alga cells now visible on hard surfaces in the streambed,” she said.
Researchers at Lake Superior State University’s Center for Freshwater Research and Education are studying didymo infestations in the St. Marys River, how the alga spreads, the risk of spread to other waters, and why such nuisance blooms are increasing – something happening worldwide.
Experts believe didymo may be unknowingly spread by recreational river users who are urged to completely clean, drain, and dry all equipment and boats when they leave a waterway, particularly one known to host invasive species such as didymo or New Zealand mudsnails.
That means removing all mud and debris, draining water from all bilges, wells and tanks, and drying equipment for at least five days or disinfect gear with hot water or a diluted bleach solution, officials said.
More details about didymo can be found at www.michigan.gov/invasives online.
Related articles:
Monarch butterflies are facing extinction, but Michigan could be a sanctuary
‘Highly invasive’ spotted lanternfly finally lands in Michigan
Conservation groups want to intervene in state, tribal treaty negotiations over Great Lakes fishing