Monday, September 14, 2020

Studying rock snot with Molly Wozniak

My name is Molly Wozniak and I am currently a senior at Lake Superior State University (LSSU) studying fisheries and wildlife management, and I work at the Center for Freshwater Research and Education as the Student Education and Outreach Assistant and a Student Field Technician. This summer, I was a Michigan Sea Grant Environmental Intern and presented my research of the effects of Didymosphenia geminata on benthic macroinvertebrates. Today, I’d like to tell you about my research as an Environmental Intern and how I became interested in my research topic. 

Here’s me holding a big pile of didymo! Photo: Molly Wozniak

Last summer, I had the opportunity to spend a few days in the field with the LSSU Center for Freshwater Research and Education Little Rapids Restoration crew that works conducting post-restoration surveys of the Little Rapids of the St. Marys River. The Little Rapids restoration took place in 2016 when a causeway separating the rapids habitat was replaced with a multi-span bridge to restore flow to the previously stagnant area. This restoration was in effort to increase spawning habitat for fishes that live in the area, particularly salmonids. Since this flow restoration, the crew has been collecting larval fishes, aquatic macroinvertebrates, and fish egg samples to determine what species are utilizing this area for spawning and development purposes. 

The Little Rapids area of the St. Marys River where I conducted my field research and worked this summer. Photo: Molly Wozniak

It was so fun to help the crew collect samples, but I noticed that when they would empty their nets into the collection containers, there was a lot of brown, slimy-looking gunk that was also collected. This mysterious gunk is actually a type of algae that is commonly referred to as “rock snot” or “didymo” (scientific name Didymosphenia geminata). I was instantly fascinated by this because didymo is an under-researched invasive species that grows on rocks in the substrate and produces long, dense stalks when it blooms, which is what the crew was collecting with our samples. Didymo is considered a nuisance due to these stalks because it has been found that they can smother the bottoms of rivers, thereby often reducing the quality of aquatic macroinvertebrates living in the ecosystem as well as being very visually unappealing to everyday recreationalists. Didymo is found throughout the world, particularly in New Zealand, where most research has taken place, but the St. Marys River is the only place it is found in Michigan. 

Stalks of didymo can be seen on the rocks from above the water in the St. Marys River. Photo: Molly Wozniak

After I first became familiar with didymo, I was so fascinated by it and was eager to learn more. I decided that I wanted to involve didymo with my senior thesis project at LSSU. This past summer, I was able to work on the Little Rapids Restoration crew and conduct my research through my Environmental Internship. My project consisted of sampling for benthic macroinvertebrates in areas with didymo and where didymo was manually removed. Finding sites to sample initially proved to be a challenge due to high water levels limiting accessibility to ideal sampling sites (and trying to put on a wetsuit for sampling was no easy task either). However, we were able to persevere and find sites that worked. 

Molly and her research mentor, Dr. Ashley Moerke, are ready for field sampling after getting their wetsuits on. Photo: Molly Wozniak

Each site had paired quadrats that were sampled for aquatic invertebrates before any didymo was removed. After this initial sampling, one quadrat at each site was scrubbed clean of didymo, acting as the treatment and those still with didymo as the control. The sites were then sampled two weeks later to see if there was any difference in the macroinvertebrates collected. After collecting my data and spending time in the lab identifying all of the aquatic insects collected, which is a beloved activity of mine, I was able to finalize my results and present them at the Michigan Sea Grant Environmental Internship Symposium.

A control plot from my research sites. Didymo can be seen heavily coating the rocks in the area and the colored rocks mark the borders of the sampling area. Photo: Molly Wozniak

I found that there was not a significant difference in the number of species of macroinvertebrates collected between the control and treatment plots and between initial and post sampling. Previous studies have shown that the tolerance quality of insects typically decreases in areas with didymo, but that did not seem to be the case in my project. This may be because it was a small area sampled (0.25m² per sampling event) or because the water quality and habitat of the area is of good quality. These conclusions will be further processed.

One of the treatment plots that was scrubbed clean of didymo for my research. It’s crazy to see the difference between the two plots! Photo: Molly Wozniak

Throughout my Michigan Sea Grant Environmental Internship, I learned so much and was able to have so many amazing experiences, like sharing my passion for my research to a broad audience at the Symposium. If you would like to learn more about didymo and how to prevent it, I created an outreach webpage as a part of my internship that is free and available to visit: and if you have any questions, please feel free to reach out to me at