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Invasive algal blooms found in Boardman River, south of TC

didymo in the water horizontal.jpeg
Michigan Dept. of Environment, Great Lakes and Energy
The brown matter is idymo growth on submerged vegetation and gravel at Shumsky’s Canoe Launch on the Boardman River, in Grand Traverse County. (Photo courtesy of EGLE)

A harmful algal bloom has been found in the Boardman River, south of Traverse City.

Scientifically, the microscopic algae are called Didymosphenia geminate. You can call it “didymo,” or use its not-quite-affectionate nickname: rock snot.

didymo mat horizontal.jpeg
Michigan Dept. of Environment, Great Lakes and Energy
Didymo stalks form mats that are coarse and fibrous, resembling wet wool or cotton. (Photo courtesy of EGLE)

“But actually, when you touch it, it’s not snotty or slimy,” said Joanne Foreman, a spokesperson for the state’s invasive species program. “It’s actually more of a wet wool feel, so it has sort of a rough texture to it.”

The name comes from its appearance, especially when viewed through water.

On Aug. 22, officials with the state’s invasive species program collected samples in Blair Township, at Shumsky’s Canoe Launch and a bridge off East River Road. They were verified the next day by the Great Lakes Environmental Center.

The invasive algal blooms had earlier been found in the Upper Manistee and St. Mary’s rivers.

When didymo blooms it can carpet the bottoms of rivers and streams, covering the food source for the little insects that fish like to eat. And unlike a lot of algae that thrive in warmer waters, didymo prefers cold, pristine bodies of water — exactly the places people like to go fishing.

That’s why the state is asking anglers, especially, to beware.

“We’re really pushing for folks that are visiting any water bodies to take extra precautions and follow the steps to clean, drain and dry your gear, before you go from one place to another,” said Foreman.

That will help prevent its spread. Right now, there’s no way to eradicate didymo once it’s taken hold in a river or stream.

The state has a list of steps you can take to help, including the following:

  • Clean and remove mud and debris from surfaces of things like waders, boots, boat bottoms, fishing gear and more.
  • Drain water from bilges, wells and tanks.
  • Dry equipment for at least five days, or disinfect it with hot water or a diluted bleach solution.

And the public is asked to report sightings in new locations. There’s an online reporting system.

Ed Ronco is IPR's news director.