by Audrey Hoey-Kummerow – Arriving at Allequash Lake early in the morning, I was filled with excitement and curiosity. I was about to get a front-row seat to the work that goes into being part of the Long-Term Ecological Research crew. Trout Lakes Station’s LTER Crew consists of three members: Jean Traudt, who specializes in chemistry; Katie Madden, who focuses on biology; and Abby Buzdon, who is dedicated to studying fish.
On this particular day, I accompanied Jean and Katie in the field, while Abby stayed behind to repair the fyke nets she will use later this summer as part of the crew’s research on fish populations in our lakes. The LTER program at TLS is part of a broader network established by the National Science Foundation in the 1980s in an effort to better understand long-term change in our ecosystems, document interactions between physical, chemical, and biological processes and uncover the role disturbances play in how these habitats work.
Over the past 40 years, the LTER program has unveiled significant insights into our local lake ecosystems. The struggling walleye fishery has had profound implications for both local biodiversity and local fishing economies. Increasing fluctuations in lake levels have affected everything from shoreline ecosystems to recreational activities. The arrival of new aquatic invaders has altered native aquatic communities, and sudden declines in lake water clarity have impacted the entire aquatic food web and the recreational value of the lakes.
Out on Allequash Lake, I got hands-on experience with some of the critical methods used to gather data for this important long-term research. Here’s a glimpse into our day:
Sampling Phytoplankton
Using a pump, we filtered lake water to capture chlorophyll, which indicates the abundance of phytoplankton – the tiny, free-floating plants that make up the base of a lake’s food web and provide the foundation for the entire ecosystem. This process is part of a bi-weekly sampling routine that contributes to a 40-year dataset on lake productivity, which is a measurement that can indicate the amount of biological activity – essentially life – going on in a lake. We had to keep the pump pressure low to avoid bursting the chlorophyll cells and processed up to 3000 milliliters of water.
Temperature and Dissolved Oxygen (DO) Profiles
Next, we measured water temperature and dissolved oxygen levels in the lake. It was interesting to watch the meters for temperature and oxygen levels both go down as it went deeper into the lake. For our lakes in Wisconsin, summer is the time for “stratification,” when the lakes separate into a warmer, upper layer of water and a cold, lower layer. Scientists call the place where the two layers meet the “thermocline” and it is here the temperature changes rapidly and can greatly influence biological processes. The dissolved oxygen data helps us locate phytoplankton, since plants give off oxygen, and understand their dynamics within the lake. In the fall, as the warm surface waters cool, the whole lake will mix again and spur a boom in phytoplankton growth.
Light Profiles
We also measured how deep sunlight was reaching into the water. Researchers call this
“light penetration” and it can greatly affect phytoplankton growth and significantly impact the productivity of the lake. An additional sample taken at a random meter, known as the “blind” sample, ensures the accuracy and consistency of our measurements.
Zooplankton Sampling
Using a Schindler trap, we collected the tiny, free-floating animals called zooplankton from specific depths to analyze their populations and behavior. Many zooplankton in our lakes undertake a daily migration through the water column. They head down to the dark depths during the day to hide from predators and then head toward the surface at night to feed on phytoplankton. These tiny creatures play a crucial role in the aquatic food web, feeding on phytoplankton and serving as prey for fish like walleye. We preserved the samples with iodine, which stains the phytoplankton for easier identification and helps in maintaining their integrity for further analysis.
Reflecting on the Experience
Being part of the LTER crew for a day was a fascinating and eye-opening experience. It highlighted the meticulous and detailed work that goes into monitoring and understanding the complex dynamics of our lake ecosystems. The data collected not only contributes to long-term ecological studies but also helps us respond to emerging environmental challenges. It’s amazing to think that crews like this one have been doing this work for more than 40 years!
Witnessing firsthand the passion and dedication of the researchers at TLS was inspiring. Their work is crucial for uncovering the mysteries of our lakes and ensuring the preservation and health of these vital ecosystems for future generations. This experience deepened my appreciation for the intricate web of life in our lakes and the importance of long-term ecological research in safeguarding our natural world.