Comment April 17, 2026
By Noelle Wood, Education and Relations Officer
IISD Experimental Lakes Area (IISD-ELA) is often referred to as a living laboratory—a place where we take studies that are typically conducted inside a lab and conduct them on living, whole-lake ecosystems.
This can also be said of some of our experimental procedures.
Over the past few years, a PhD candidate from Lakehead University, Cody Veneruzzo, has been working with Dr. Michael Rennie to construct an in-field lakeside respirometry setup using respirometry tanks to determine whether the presence of microplastics in a lake affects the metabolic rates of three common freshwater fish species.
This is all part of ongoing work at the world’s freshwater laboratory to determine the impacts of plastics on freshwater systems.
Our metabolic rate is the amount of energy we—or any organism—expend to support our basic body functions, such as breathing, digesting, and repairing cells.
The rate at which we expend this energy also varies throughout the day, depending on what activities we are doing. For example, the number of calories you burn while you’re asleep will be significantly less than the calories you would burn if you were to run as fast as you can.
This is because our bodies require different levels of oxygen to meet specific needs and prevent cell death. These rates can be monitored by measuring how much oxygen we consume over time.
First, we collect white sucker (Catostomus commersonii), lake trout (Salvelinus namaycush), and yellow perch (Perca flavescens) from the experimental microplastic lake and nearby reference lakes. These fish get placed in respirometry tanks on the shoreline of the lake from which they were captured (pictured on the left).
In these tanks, we can measure and record how quickly each fish consumes the available oxygen within the sealed chambers. Usually, the highest rate of oxygen consumption occurs when the fish is first placed in the chambers or after a period of high activity—likely due to stress from being in a new environment, and cells needing more oxygen after exercise (just think about how humans breathe faster as we exercise).
Conversely, the lowest rate of oxygen consumption is measured once the fish has adjusted to its new environment and its cells no longer demand high levels of oxygen to function (just like when humans are asleep).
Every 15 minutes, the chambers are replenished with fresh lake water, providing the fish with fresh oxygen. To reduce any additional stress, the tanks are covered with lids and a reflective tarp. As Cody says: “It’s all about the fish!”
This technique is rarely used in the field due to the many logistical challenges of keeping the monitoring equipment outside with limited access to electricity. Additionally, we used wild-caught fish, and once testing was complete, all fish were returned to the lake from which they were caught.
Here at IISD-ELA, we also have the luxury of returning to the same sites year after year, which allows for continuous monitoring and comparisons between lakes and over time.
Once we know the maximum and minimum metabolic rates of the fish, we can determine their overall energy capacity for regular activities, such as growth, swimming, and reproduction. We can then directly compare fish metabolism data collected before, during, and after a whole-lake microplastic addition with those from an unimpacted reference lake.
How might microplastics be affecting metabolic rate?
Imagine you are a lake trout who has spent the afternoon out hunting. You have swum great distances to feed for the day, expending quite a bit of energy, and your cells need to recover. This energy will hopefully be replenished by the food you have consumed, but what if, instead of calorie-rich minnows, you were consuming microplastics?
So even though you are consuming the same volume of food, you are ingesting far fewer calories. This can force your metabolism to change, as your cells need to adjust their energy expenditure to avoid running out of fuel. Reduced energy return after hunting could potentially lead to other health risks, such as changes to growth and development.
Cody wrapped up his final year of respirometry work at IISD-ELA in the fall of 2025, and through his work, we learned about what goes on in our lakes at a very fine scale. Watch this space for updates on what this research revealed.
Gaining a better understanding of how human contaminants affect freshwater species helps inform the next steps to protect them, including changes to policies that protect them and our daily habits.