Rock Snot Invasion

(gentle whimsical music) - [Bret] It's a thick and slimy golden brown goo.

It's called rock snot, (sneezes) and it's invading our north shore streams.

(gentle whimsical music) - [Mark] The organism that makes this snot is a type of algae that is called a diatom.

It's about a 10th of a millimeter long.

You can't see it with a naked eye unless it grows in these big, huge masses.

And then it looks like snot.

And these diatoms, didymosphenia, lives on a big mucilage stock.

The diatom might be this long, but the stock that it produces is this long.

They're trying to do is, you know, they're living on a rock, and they're trying to get up to the, you know, where the water is the best and full of oxygen.

But to do that, they just have to keep growing.

Didymo is actually native in the country.

It has lived fairly happily on the shore of Lake Superior, and people don't notice it too much.

So the crazy thing that's happened in Minnesota is this is the first time we've seen it in streams in Minnesota, is these invasions of our North Shore streams here.

(gentle pulsating music) First time it happened was 2018 in the Poplar River - [Heidi] One of the fisheries staff at the Grand Marais, his name's Matt Weberg.

He noticed didymo in the Poplar River, and he called me.

- [Mark] got her a sample, she sent it down to us and looked at it and said, "Oh yeah, this is didymo."

- [Heidi] I contacted Mark 'cause I thought he'd be interested.

He's an internationally known diatom expert, so he's a real big deal in the diatom world, and he's very enthusiastic.

- [Mark] Clearly wasn't like a gob of something from Lake Superior that have been put up there because all of the other diatoms and algae that were in this sample weren't the stuff we find in Lake Superior.

(gentle pulsating music) Our next step was to try to find some funding sources where we can, you know, tackle this problem and get a handle on it.

On the current project where we're working on the rivers and nearshore area of Lake Superior was funded by LCCMR and projects started in August of 2021.

Didymo really is the triple threat to a stream.

It affects the ecology of the stream.

It affects recreational opportunities of the stream, and it affects the economies because people come up to enjoy the North Shore and enjoy our North Shore stream.

You know, you start trying to, you know, fly fish in this sort of stuff with all this goo on the rocks.

Instead of catching fish, you're gonna catch snot.

(chuckles) We saw it here in this stream right now.

It's probably close to an inch-thick coating.

Every rock, every rock out there is being just coated with a bunch of goo.

(upbeat ambient music) (gentle amorous music) So once a year, we do what we calling our blitz, and we hit everything from the Lester River all the way up to Grand Portage Creek, and we hit about 25 different streams, and then their corresponding lake sites as well.

- [Bret] Mark Edlund starts by testing the water depth and how fast it's flowing.

Researcher Joe Mohan uses probes to measure water temperature, salts, chlorophyll, and pH levels while Heidi Rantala captures insects.

- So I'm collecting stream insects with this device called a surber sampler, and it uses water flow to catch bugs in a net.

So I face the net downstream.

I usually pick out some of the big rocks first if I can, so that I can make sure that they get really clean, and I disturb the bottom and it causes the bugs, the insects to float up, (water sloshing) and it catches all the stuff.

And so, here's an example of one of the bug or one of the rocks that I collected.

And you can see the didymo on it.

A lot of the aquatic insects actually live on the sides or underneath of the rocks, not on the top where the didymo is growing.

So I brush all sides, and then I also take what's in this net and I put it in my bucket too.

And then to concentrate it, I just pour it through a soil sieve, which is a fine screen.

Oh, I see one little mayfly scurrying about in there but otherwise, I don't see a lot of bugs in this.

And then, I just save it in a Whirl-Pak which is just a brand name of these little plastic bags.

I just put my garbage in it so it doesn't litter the stream, and then I preserve it with ethanol, just alcohol.

I'll take these back to the lab at French River, and what I have to do then is to pick the insects apart from all of the didymo which will take quite a long time.

I'll do that under a microscope similar to the one that Mark is looking through right now.

That looks like, to me it looks like wet wool.

And I actually can see some insects.

They get killed instantly from the ethanol but it helps to preserve them so they don't get broken down by bacteria.

Stream insects are important food for our fisheries, and in places around the world where didymo is an invasive.

We've seen big changes in the stream insect communities.

It'll go from things that are really good, chunky fish food, things like caddisflies, and mayflies, and stoneflies to insects that are more kind of filiform body shape.

So things like fly larva, maggots, or actually some aquatic worms too.

- [Bret] Mark has the slimiest job.

He uses a Loeb sampler to scrub snot off the rocks and then suck it into tubes.

(water sloshing) - [Mark] So we've just gotten done collecting a whole bunch of the didymo and snot from the Devil Track River here into this bottle.

One of 'em, we're gonna use to look at how many diatoms and algae are there.

One, we're looking at what kind of bacterial community is found in these mats of didymo.

And the other is we're looking to figure out where the didymo came from.

And so, we are looking for a genetic signature specific to didymo, comparing it among the streams that have didymo to the big lake that has didymo, and then we have colleagues throughout the country who are sending us their snot samples.

(chuckles) (gentle chiming music) We're in the microscope lab at the St. Croix Watershed Research Station.

It's a lab that we've outfitted with some of the best microscopes that you can buy to look at very, very small things.

Diatoms are one of our groups of microscopic algae.

They're specialized because they have a little shell around them that's made out of biologically produced glass.

They take silica that's dissolved in our water, pull it into their cells, and they can polymerize glass.

And we can see in here, you know, the beautiful live didymo, they're good-sized cells that are in there.

They're healthy.

They have a golden brown chloroplast that is taking energy from the sun, doing photosynthesis, creating oxygen, creating sugars for themselves.

But we also see in there is that the diatoms are living on their stock.

There's two didymo in the picture right now, but their stocks' going all over the place, and it's that stock that is really the, you know, the mucus that we see in this rock snot layer.

That matte itself becomes its own sort of an ecosystem that this didymo is controlling.

And what that does is it changes the biology in ecology of the streams.

In particular, we see different algae that live within this mat of goo.

We see different bacteria.

We even see different insects that live in the goo.

So we're studying it.

When we were out last week with Heidi, she was collecting the aquatic insects that are part of the, you know, the food web.

She's gonna go through, pick 'em out, identify 'em, and then we're gonna see what they're eating.

So we'll see who's eating didymo or if anyone is eating didymo.

(gentle pulsating music) (gentle music) We've known that it's lived in the Great Lakes.

Said it was reported in Lake Michigan in the 1870s.

The first report we've had from Lake Superior was from the early 1960s.

I would expect that it's been in Lake Superior for thousands and thousands of years.

We just don't have a record of it.

(gentle pulsating music) We know that it had been living happily in places like Alaska, some of the rockies, you know, mountain streams and things like that.

But what's really been sort of shocking is where it's appeared in other places, you know, where it's never been seen before.

It has, you know, really shown up in, you know, abundant masses of it in places like Montana, Wyoming, Colorado, Utah, New Mexico.

And then we head east, you know, Oklahoma, Arkansas, Tennessee, New York, Vermont, Connecticut, you know, places that, you know, we had not experienced didymo in these places before and it's now growing there.

Places that are, you know, some of our nicest streams, you know, cold water, low-nutrient streams that we don't expect to, you know, have problem algal outbreaks in them.

The first things that we want to do is prevent it spread.

Clean in, clean out.

When you go into a stream, make sure your boots are clean, your boots are dry, your gear is clean.

When you leave the stream, let's clean it again.

We don't understand, you know, how the North Shore is gonna respond to it, and our North Shore streams are gonna respond to it, but that's what we're working on, spending our research effort to understand this brand new phenomenon on our North Shore streams.

(pulsating ambient music)