(playful music) - [Brett] Cyanobacteria, known as blue-green algae, produces toxic blooms that can be harmful to animals.

The aquatic plant often shows up in waters polluted with nutrient runoff.

Now, surprisingly, blue-green algae is also being detected in some of our most pristine wilderness environments and researchers at the St. Croix Watershed Research Station are trying to figure out why.

(playful music) - We actually first noticed this in lakes on Isle Royale National Park, one of the most protected places in the world.

And it's located on an island in the middle of Lake Superior.

So what could be going on to cause algae blooms in these lakes?

You know, we usually attribute algae blooms to things like pollution, either coming from agriculture or urban environments that are close by that we can clearly track the source to the water.

Here, there's no obvious connection like that.

As we work on it more and more we're kind of realizing that this actually been may have been going on for decades.

It's just that because of the remote nature of these lakes, often this will happen without anyone noticing or commenting on it.

Through kind of a increased awareness, both from citizen, scientists who are out there backpacking in the boundary waters or elsewhere, as well as the use of remote sensing, so actually satellite imagery, we've been able to start to pick these things up more frequently and realize that this is more widespread issue than we initially thought.

And so we think it may be changing weather patterns that might be related to a changing climate, as well as sources that don't respect boundaries.

So atmospheric sources.

So the actual transport of nutrients through the air, whether that be through ash and forest fires, through dust that's just we know is moved continentally.

And so we actually have set up a monitoring network that basically boxes in our sites in the Superior National Forest that's measuring dry fall as well as nutrients and precipitation.

So we can get a handle on how much of an issue this could be.

(playful music) (bright music) - [Brett] Not all algae is toxic, like a filamentous variety found in the backwaters of the Saint Croix River.

- Here, you can see there's a lot of algae growing in the water and it's this sort of beautiful green, slimy stuff.

It's not dangerous or bad.

It looks a little nasty, but it doesn't produce any toxins or anything like that.

It's a group that's called Spirogyra.

You can feel that they're big, they're slimy.

They form these long, long filaments.

And what they're doing is they're loving the fact that it's the water temperature's gotten a little cooler, there's a lot of nutrients still in the water, and they're loving that it's nice and sunny today.

So you can see there's even bubbles in the mats of algae because they're photosynthesizing, producing oxygen.

- You know, it does look a bit slimy and probably isn't the people's favorite thing to wade through, but it's actually not cause for alarm at all.

- [Brett] Non-toxic algae may actually help control cyanobacteria.

- It produces oxygen and it competes with those cyanobacteria.

So it helps keep them from being able to take over a system.

If you have a healthy non-toxic algae population, of course, they're all competing for the same nutrients and light.

And so, having these here kind of protects some of these systems from being taken over by those nastier types of algae.

A lot of people, they think of aquatic plants as a nuisance, and some of the invasive ones definitely are, like curly-leaf pondweed and Eurasian milfoil.

But the native plants are actually our best defenders against harmful algae blooms in our lakes because they basically suck all that phosphorus and nitrogen right outta the water and they hold it in their biomass all summer long and basically keep it away from the cyanobacteria.

And there's actually a whole body of science that tracks how when you lose aquatic plants, you flip lakes over into this what's called a plankton or algae dominated state.

Those aquatic plants are usually a sign of good health because they can only grow where you have good transparency, good light penetration.

And they also are a good way to protect to your lake from those kind of nasty algae blooms that could come if they weren't there.

(light music) - [Announcer] Stories about research into invasive aquatic algae, plants and animals are sponsored in part by the Aquatic Invasive Species Task Forces of Wright, Meeker, Yellow Medicine, Lac Qui Parle, Swift, and Big Stone counties.

We can stop aquatic hitchhikers from infesting more lakes and streams by cleaning up everything we pull out of the water.

It's a simple drill.

Clean in, clean out.

Before leaving a water access, clean your boat and water equipment.

Remove and dispose of all plants and aquatic species in the trash.

Drain water from your boat, ballast tanks, motor, live well, and bait container.

Remove drain plugs and keep drain plugs out while transporting equipment.

Dispose of unwanted bait in the trash.

To keep live bait, drain the water and refill the bait container with bottled or tap water.

And if you have been in infested waters, also spray your boat with high pressure water.

Rinse with very hot water, dry for at least five days.

Stop the spread of AIS.