We’re back with CFL postdoc Tyler Butts and his team as they explore how invasive species interact with eutrophic lakes. As you may have noticed, they are a dedicated crew!
by Madelyn Anderson – When I first met undergraduate invasive species technician Joey Munoz, he had a pile of live zebra mussels in front of him and was diligently scrubbing every single one with a toothbrush. He explained he was preparing them for life in the lab, where they’d serve as a living population for a key part in Butts’ research mosaic: mesocosms.
Put simply, a mesocosm is an enclosed amount of water in a tank that can be manipulated to represent natural conditions. Munoz and his fellow researchers are placing their carefully scrubbed and prepared zebra mussels into these mesocosms and simulating lake environments for twenty four hours, so that they can study the interactions that take place between zebra mussels, microbes, and algae.
Butts’ team performs a typical mesocosm “run” every other week at the lab, carefully working through five steps. The process begins with collecting eight buckets of lake water, or seston, from Lake Mendota, which is then divided in two. Half of the samples are left swimming with algae and zooplankton, while the other half are filtered through 106 micron mesh to remove most zooplankton grazers, leaving the algae behind..
Once the natural and filtered seston is ready, it’s transferred to vats containing sets of three tanks, which may fall into four categories. One will have no zebra mussels or zooplankton, one will have both, and the remaining two will have one of each. These tanks are then sampled four times throughout the run: at the beginning of incubation, 3-4 hours later, 8 hours later, and 24 hours later.
The data Butts collects from these experiments will give him a better idea of how zebra mussels affect microbial communities and algae concentrations in the waters they inhabit..
Today, Munoz measures the amount of cyanobacteria in the vats while his colleague Megan Perkins collects water for later nutrient analysis. Together, the two are piecing together the puzzle not only of what is going on in their mesocosms, but also of what may be happening in Lake Mendota. Which microorganisms are being filtered out? Which are left behind? How do zebra mussels play a part?
“This experiment is marrying the macro and micro,” said Perkins. “It could yield interesting data we haven’t seen.”
“I like to think of lakes as a Jenga tower,” Butts added. “These experiments let us look at the ways we can arrange things so it doesn’t fall, whether that’s a big cyanobacteria bloom or another event, as easily. How does food web structure change things? That’s what I’m really interested in.”
While there is much to look forward to with the future of these mesocosm runs, they are also connected to the past. By studying zebra mussel, algae, and microbe interactions in an experimental context, researchers can tie this work to long-term records. The North Temperate Lakes Long-Term Ecological Research project (NTL-LTER) has decades of related data on Lake Mendota, in addition to long-term microbial records from the McMahon Lab, run by UW-Madison professor of bacteriology and civil and environmental engineering, Trina McMahon.
“Invasive species impacts are really difficult to predict, and we have a unique opportunity here with the length of data through NTL-LTER and the Microbial Observatory,” said Butts. “We can get at some of these difficult questions like interacting drivers that cause changes in Lake Mendota and use that to manage our systems in the future more adaptably.”
The mussel mystery in Madison’s waters is interconnected, spanning diverse experiments, people, and perspectives. As Butts’ team carries on unthreading the science, they are supported by a history of curiosity and a future full of connections.
“At heart I’m an ecosystem scientist, and limnology is a great way to do that,” said Butts. “Especially with the interactions from microbes and plankton to fish and bugs, this project can tell us a lot about how systems operate and how they might respond to change, which really excites me.”