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Complementing fish movement data with water chemistry

By Miracle Denga, Undergraduate Honours Thesis Research Student, Department of Biology, Trent U Limnologists have always been interested in studying the vertical patterns of lake variables like temperature and dissolved oxygen. Thanks to recent improvements in the sensors used for water monitoring, we can now look at the vertical patterns of many variables in water at incredibly high resolution. A vertical profiler (we use the RBRmaestro³ Multi-Channel Logger, as seen in the pictures below) is a sensing tool that measures different lake variables as you lower the instrument into the lake, including dissolved oxygen, temperature, chlorophyll a, pressure, and several others. These advanced vertical profilers can take eight measurements of each of the above variables per second, creating an extremely detailed image of how lake conditions vary with depth. The data that a profile generates are incredibly useful – they can tell us the different phases the lake is in; for example, whether it's stratified or well mixed. The profiler data can also show us the amount of oxygen available to creatures at the bottom of the lake and provide an estimate of how much phytoplankton is in the water column. The information gained with a profile can give us baselines of what a lake should look like and help understand the factors that cause lakes to change (for better or worse). Ultimately, these sorts of data can be useful for developing best practices for lake management which are undeniably of benefit to stakeholders and to the creatures living in the lake. Below you can see some of the data we collected on Stoney Lake this May.

About me: I am an undergraduate student at Trent University doing my honour’s thesis in Dr. Marguerite Xenopoulos’ Aquatic Ecology Lab. I am investigating the factors affecting differences in the rates of deep-water oxygen depletion in the Kawartha Lakes, which involves taking monthly vertical profiles from a selection of Kawartha Lakes over the summer. This work started in May and Stoney Lake is one of the lakes we are focusing on. Stoney was profiled intensely once last summer with the intent of creating a 3D distribution of the lake variables listed above (done by Drs. Raby, Frost, and Pearce, see link). This year, I will continue sampling Stoney throughout the summer and fall. The data will be paired with data on fish tracking to see what drives fish movements and get a better sense of the dynamics of water quality in the system.

(Above) Deploying the RBR profiler in Stoney Lake on May 12.

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