Invasive ‘Rock Snot’ Found In Upper Manistee River

An invasive algal species native to Lake Superior has been found in upper Manistee River in Kalkaska County.

This is the first time that the species, didymo, nicknamed ‘rock snot,’ has been found in the Lower Peninsula. Didymo On A Rock

“It’s called rock snot because when you see it it looks a lot like snot that’s just growing off of the rocks,” says Little Traverse Bay Bands of Odawa Indians water quality biologist Sam Day. “But it’s kind of a misnomer because when you actually pick it up and rub it between your fingers it’s really more of a more of a wet cotton like feel

Day made the discovery while on a fishing trip November 14.

“We’re just floating down the river doing some fishing, casting towards banks and I happen to take a look down at a branch that was submerged and I saw what I thought was was a didymo based on some of my previous experience in school,” says Day.

Stop Aquatic HitchhikersDay, studied didymo while a graduate student at Tennessee Technological University. He was also part of the group that discovered didymo when it was first discovered in the St. Mary’s River in Sault Ste. Marie in 2015.

“Now this marks the first occurrence of it in the Lower Peninsula that we know of,” says Day. “Now what we need to figure out is where else is it in the state so kind of the next step I think is to get boots on the ground and start surveying different rivers that we think that could likely be in.”

Fortunately, the species doesn’t pose much of a threat to humans like the cyanobacteria blooms found in Lake Erie. But it can cause harm to the ecosystem.

“The main problem with didymo is it has the potential to form these these big blooms, or mats we like to call them, that can completely cover the streambed and when that happens it really limits the habitat that’s available for a lot of macroinvertebrates, or bugs, those bugs are really important food for trout and other fish,” says Day.

Day says the bloom has grown significantly since his last visit to the area near Fife Lake. It’s presence in the area suggests it may be elsewhere in the lower part of the state. It’s not good news for trout fisheries in the area.

“Generally it It does need to be in kind of shallower areas so that it can be able to get sunlight,” says Day. “You won’t typically see it in very deep holes, but anywhere where it’s it’s pretty shallow and there’s some moving water you’re pretty much going to see didymo.”

The species spreads primarily on boots and waders of anglers.Day Cleaning Off Gear

“Anything that comes in contact with the river could potentially be a way of spreading,” says Day.

The steps to prevent the spread are letting boots and gear dry off before using. And evening cleaning them off with a 2 percent bleach solution. It also helps if people report the invasive species if they see it whether white, yellow or light brown.

LTBBOI is currently working on putting together monitoring plans next year. Michigan Department of Environment, Great Lakes and Energy is also monitoring the species.

Day says monitoring may include picking up rocks, scrubbing them and collecting samples.