Photo: Story Scouts gather around Dr. Mark Edlund to look at rock snot through a high-powered microscope. Photo courtesy of Anne Brataas. 

By Laura Durenberger-Grunow - Boreal Community Media - Updated April 8. Originally published on April 4, 2025

Rock snot is an alga that looks exactly as it sounds - like snot. Rock snot was first recorded in Lake Superior in 1961 as a natural part of the lake. However, in 2018, it was discovered in the Poplar River near Lutsen, and it continues to spread every year. Being a relatively new discovery, many people aren’t familiar with Didymosphenia geminata, didymo for short, or, as it’s commonly known, rock snot. But a local group of kids aims to change that with the new book Go Away, Rock Snot! A children’s field guide to the latest invasive species threatening North Shore streams. 

 A "rock snotter," an imaginary rock snot predator that the Story Scouts kids created as part of the Go Away, Rock Snot! story is shown on the front cover of the book. Cover image courtesy of Minnesota Children's Press. 

38 Cook County kids, aged 5-12, worked for almost two years with Anne Brataas, chief creative officer and founder of Minnesota Children’s Press, through her program Story Scouts to create a book about didymo. The finished product is a true, evidence-based science story with a creative twist, involving a puppy preschool and some mischievous pups—all imagined, written, illustrated, and edited by the kids. And on April 8, Brataas and some of the Story Scout kids will host a book release party at the Johnson Heritage Post in Grand Marais, from 3:30 p.m. to 6:30 p.m.

 The back cover of Go Away, Rock Snot! shows a photo of the kids working with Dr. Edlund and his team, a hand-drawn illustration, and a description of the book. Back cover image courtesy of the Minnesota Children's Press. 

The book idea began when Brataas was connected with Dr. Mark Edlund of the Science Museum of Minnesota’s St. Croix Watershed Research Station through MN Department of Natural Resources scientists. For over 35 years, Dr. Edlund has been studying diatoms, a type of algae, distinctive for containing "glass-like cell walls made of silica, a hard mineral found in sand that can help protect diatoms from predators." Or, as he told Boreal Community Media, “the coolest organisms on the earth.” Dr. Edlund first learned about rock snot in the 2000s, when scientists and some of Edlund’s colleagues began studying the algae around the world. “Places that had never been seen with didymo were suddenly getting large growths that were impacting streams--how they looked, how they functioned, how people could interact with them.”

Scientists believe that rock snot is naturally found in cold water lakes around the world, like Lake Superior, and grows in bodies of water in colonies or big, thick mats.“It sometimes presents itself as pretty gross, but the wave action of Lake Superior seems to make those instances pretty uncommon,” Dr. Edlund shared. However, in some cases, like when it is introduced into streams or rivers, it can become invasive or aggressive. (Native species can also become aggressive and cause ecological and economic damage, but are not scientifically considered invasive. A local example is spruce budworm.) If not naturally found in a particular stream or river, these clumps can take over and lower water quality for recreational usage, disrupt native ecosystems, and smother stream bottoms, causing native species to relocate due to a lack of food. 

In 2021, his team received its first batch of funding and began sampling various rivers and streams around Cook County. “We immediately noted it in several rivers, including Poplar, Onion, Devil Track, Kadunce, and Kimball. We've also noted it in smaller abundances or in random years in Two Island, Carlson, Flute Reed,” Dr. Edlund said. 

Since then, they have maintained funding to monitor 25 streams and rivers along the North Shore yearly. “We will soon have our 2024 data compiled to see where it may have spread or shown up,” he added. 

Like many invasive species, humans are one of the main spreaders of rock snot. Dr. Edlund added that pets can also contribute to its spread by carrying it between different streams in their fur. “One of the main vectors that has been targeted are felt-soled waders that are commonly used by anglers. The felt pads at the bottom help prevent slipping on rocks but remain wet and can harbor microscopic organisms like didymo and fish pathogens for several days,” he shared. 

With the spread of didymo from Lake Superior to surrounding rivers and streams becoming more prevalent, the book is a tool that can help spread awareness of the alga, the issue, and ways to prevent its spread, which is where the Story Scouts come in. Dr. Edlund and his team (along with guest teachers from the Science Museum of Minnesota) visited Cook County and worked with the kids to sample rock snot in Grand Marais Harbor, study the organisms they collected through a high-powered microscope, and gain a scientific understanding of stream ecology and invasive species. 

 Story Scouts work with Dr. Edlund and his team in the summer of 2023 to sample and identify rock snot near the Grand Marais Harbor. Photo courtesy of Anne Brataas. 

Thanks to support from grants from the Legislative-Citizen Commission on Minnesota Resources and Minnesota Sea Grant, Dr. Edlund said working with the kids, “Was full immersion rock snot! With Anne's help and encouragement, we came prepared on the first day to get the kids sampling with boots and gear in the Grand Marais Harbor, get them looking through the microscopes at samples to show them what that goo on the rocks really looked like.” 

 The kids were able to use high-powered microscopes to view rock snot, or didymo. Photo courtesy of Anne Brataas. 

From there, the kids worked together with Brataas, an award-winning science writer who received her master’s degree in zoology (specializing in ichthyology (fish) and limnology (lake science)), to create an imaginative story to complement the scientific aspect and design the illustrations for the book. “Kids are so capable,” she shared with Boreal Community Media, before adding, “kids want to do meaningful and good things. They can come up with creative solutions to problems, and, to be honest, they’re the ones kind of leading the environmental movement and creating change right now.” 

Each week in Story Scouts, the kids would “popcorn” ideas aloud, with Brataas taking notes. These ideas would then form the basis of a creative story that complemented the scientific information they'd learned. Brataas would then organize these ideas into a more structured format at home and bring them back to the next session, where the process would repeat until they had a complete draft. The kids also helped illustrate the book, with 128 hand-drawn pictures making the final copy. 

As part of a group Brataas runs called the Comma Club, along with a class from Great Expectations School, some of the kids helped edit the 55-page book. After that, she shared that “Professional copy editors and scientists scrubbed for errors and fact-checked it.” Dr. Edlund was one of the professional scientists who reviewed the book. He said, “The kids took these ideas, ran them through their incredibly imaginative minds, and used art, storytelling, and science to help us all solve the problems of rock snot.”

But the book goes beyond creating something informative and “cool”. Brataas said they created something they will always be part of, and something they are hopefully proud of. “The kids are the true artists and illustrators. The book is registered with the Library of Congress and has an International Standard Book Number (ISBN). The kids hold the copyright for all the art they create within Story Scouts,” she said. 

With the book officially in print, Minnesota Children’s Press is hosting a book release event at the Johnson Heritage Post Art Gallery on April 8, from 3:30 - 6:30 p.m. The first 50 attendees will receive a free copy of the book, and some of the Story Scouts themselves will be on hand to sign books and talk about their experiences. Dr. Mark Edlund of the Science Museum of Minnesota’s St. Croix  Watershed Research Station will also be at the event, along with his high-power, large-screen microscope, where he will be showing rock snot samples from North Shore streams. 

Copies of the book will be available for purchase, and the proceeds will support Story Scouts’ workshops, book production, and printing costs. Brataas shared that she also hopes the proceeds will be used to fund future field trips to places such as the Great Lakes Aquarium in Duluth, the children’s book archives at the University of Minnesota Twin Cities, and water-quality labs at Minnesota colleges and universities.

The book will also be sold online in May and eventually in local stores. 

For more information about Minnesota Children’s Press and Story Scouts, visit minnchildpress.org and storyscouts.org. 

For large quantity book orders and discounts, email anneATminnchidpressDOTorg.