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With golden brown algae, searching for answers leads to more questions

An aerial view of Torch Lake shows mats of golden brown algae on the lakebed disrupted by scrapes from boat propellors. The benthic algae grows along the bottom of Torch Lake, and several other northern Michigan lakes, in thick mats. There is no evidence it is toxic, but residents say its growing appearance over the past decade has changed the character of the lake, and could indicate changes in water quality. (Photo: Art Hoadley)
An aerial view of Torch Lake shows mats of golden brown algae on the lakebed disrupted by scrapes from boat propellors. The benthic algae grows along the bottom of Torch Lake, and several other northern Michigan lakes. There is no evidence it is toxic, but Torch residents say its increasing appearance over the past decade has changed the character of the lake, and could indicate changes in water quality. (Photo: Art Hoadley)

A mysterious algae first started to coat northern Michigan lakebeds about a decade ago. After years of research, scientists and residents are left asking the same question: what has changed in the water that's causing it to grow?

There’s some ugly algae showing up in northern Michigan lakes lately.

We know what it is. We know it’s not a health hazard. But it’s scummy, scuzzy, crusty and gross. And people want to know why it’s here.

But even after years of research, certain pieces of the puzzle still aren’t fitting together.

Much of what we do know about golden brown algae is thanks to citizen scientist volunteers on Torch Lake, like Rick Doornbos and Greg Fredericksen.

It’s a sunny Friday morning on the lake, and Doornbos and Fredericksen are on their hands and knees, leaning over the side of a dock.

Doornbos holds a pooper scooper, while Fredericksen waits at the ready with a Petri dish and a spatula.

Doornbos carefully dips the pooper scooper into the water – not for dog droppings, but to scrape up some of the lakebed.

Rick Doornbos is a citizen scientist who helps collect golden brown algae samples for further research. He's also currently the vice president and chair of the water quality committee of the Three Lakes Association, a lake association that has funded research on golden brown algae over the past several years. (Photo: Ellie Katz/IPR News)
Rick Doornbos is a citizen scientist who helps collect golden brown algae samples for further research. He's also currently the vice president and chair of the water quality committee of the Three Lakes Association, a lake association that has funded research on golden brown algae over the past several years. (Photo: Ellie Katz/IPR News)

He pulls up a crusty, chunky scoopful, and Fredericksen uses the Petri dish like a cookie cutter, to collect a perfect circle of sediment. They place the sample inside of a funnel, then use a squirt bottle to push some of the sample through the funnel’s neck and into a baggie.

“That’s our first sample of three,” says Fredericksen. “And then we’ll put that baggie with our other baggies … in a cooler.”

The samples will be sent to the University of Michigan Biological Station in Pellston, where biologists will test them and add the results to a growing body of research and data on golden brown algae.

It’s part of an ongoing research project funded mostly by lake residents through the Three Lakes Association and the Torch Lake Protection Alliance — and much of the data collection is done by volunteers.

Volunteer and Torch Conservation Center board member Trish Narwold has watched the lake’s iconic sparkling blue waters become suddenly interrupted by patches of yellow, gray and brown.

“There’s a grief process, just like [with] other things” says Narwold. “Then you come to accept it. I mean, this is an ecosystem. This isn’t a pool.”

Narwold says this ugly, slimy nuisance algae is a wake-up call: it’s making people more aware of the lake as an ecosystem and the role they play in it.

“We don’t always understand what we can’t see. Now we have something we can see. So now we’re alerted, and we need to take the right steps.”

SEARCHING FOR AN ANSWER

Years ago, Narwold and other volunteers took the initial step of reaching out to Jan Stevenson, a retired professor of integrative biology at Michigan State University.

Along with colleagues Rex Lowe and Patrick Kociolek (both of whom work at University of Michigan Biological Station), Stevenson has helped lead research on golden brown algae in northern Michigan.

“Whenever you see a change in environmental conditions… [it] gives you pause that there must be some human activity that’s causing that,” says Stevenson. “Is this the canary in the coal mine?”

After almost nine years of research, we still don’t know the answer to that question.

But Stevenson says we know a lot more than we did ten years ago, when residents first started to notice tightly-woven mats of golden brown algae along Torch’s lakebed.

“We know much more about its species composition, and we know more about how that changes during the summer,” says Stevenson.

Golden brown algae is a combination of cyanobacteria, fungi and diatoms — tiny individual cells of algae that can colonize.

There’s no evidence the cyanobacteria in the algae produce toxins that are hazardous to health. And thanks to aerial photos, we know where in the lake it grows.

But there’s still one big question researchers are trying to figure out: what’s changed in the water that’s causing it to grow?

“We targeted one [hypothesis] to begin with,” says Stevenson. “It seemed like a pretty obvious problem associated with groundwater contamination.”

They thought that groundwater, which seeps in through the lakebed, might be bringing in excess phosphorus from sources like septic systems.

It seemed obvious for a few reasons. One, a little extra phosphorus can cause explosive growth of algae and other aquatic plants in freshwater. That’s happened all over the Great Lakes region.

Two, golden brown algae in Torch Lake grows in thick mats along the bottom, which is where groundwater seeps into the lake.

But after years of research and poring over lake records, Stevenson and the Three Lakes Association team found something surprising.

A NEW HYPOTHESIS

“Phosphorus is decreasing and has been decreasing in the lakes of northern Michigan for maybe a couple of decades,” says Stevenson. “So then the question becomes: how could a decrease in phosphorus increase algal growth on the bottom of lakes in northern Michigan?”

That’s the basis for their current hypothesis, even though it might seem counterintuitive.

“Having more algae grow in low nutrients, low phosphorus in particular, really does flip the paradigm,” says Stevenson.

Typically, more phosphorus means more algae and plant growth in freshwater ecosystems. But not necessarily in this case.

Stevenson says one good example of this is in the Florida Everglades. There, phosphorus went up and tightly-woven mats of algae disappeared.

Plus, Stevenson says some of the diatom species in those Florida mats are the same as the ones in the Torch Lake algae, including one species that shows up in the Torch Lake mats when they’re at their thickest in late summer.

“Its name is Encyonema evergladianum,” Stevenson says. “And it was named for being unique in the Everglades, until we found it here.”

(Stevenson says E. evergladianum has also been found elsewhere.)

He says there are a few theories for why phosphorus in northern Michigan lakes is going down and algal growth is going up.

It could be Quagga and zebra mussels removing phosphorus from the water column as they pull in and filter out particles.

It could be nitrogen depositing into the water from the atmosphere after decades of heavy nitrogen fertilizer use around the globe. That deposition could be changing variables like the lake’s growing conditions, the ratio of phosphorus, and the composition of different algal species.

It could be a combination of several of these theories, or something else entirely.

Stevenson says we don’t know enough to really form a full picture yet. So he and the Three Lakes Association volunteers are going to keep sampling and searching for what in the lake is causing golden brown algae to grow.

And starting this year, the U.S. Geological Survey is joining in too. Their research will focus on what human and natural factors are changing the chemistry of the lakes,

Between those two projects, the Three Lakes Association and Torch Lake Protection Alliance hope to get some answers.

Trish Narwold holds unaffected rocks over rocks covered with calcium carbonate precipitate, a chalky gray substance. She says as a Residents say they first began to notice calcium carbonate precipitate, which puffs up into clouds around footsteps, in the 1990s and early 2000s. Golden brown algae first began to noticeably appear around 2013. The algae forms calcareous mats along the lakebed, which contain calcium carbonate precipitate. (Photo: Ellie Katz/IPR News)
Trish Narwold holds unaffected rocks over rocks covered with calcium carbonate precipitate, a chalky gray substance. She says as a child she could see the colors of the rocks throughout the lake. Residents say they noticed calcium carbonate precipitate before golden brown algae first began to noticeably appear around 2013. The algae forms calcareous mats along the lakebed, which contain calcium carbonate precipitate. (Photo: Ellie Katz/IPR News)

Back on the water, Trish Narwold says she wants those details, but also hopes something bigger comes out of all this research:

“I hope for a greater understanding of the system … and awareness by the people who live around it, how to care for it, and protect it in that regard.”

Ellie Katz joined IPR in June 2023. She reports on science, conservation and the environment.