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| Bob Moe retrieves a water sample, using a tube to sample 6-1/2 vertical ft of the water column, rather than just the surface. |
The Bear Lake Association is proud to participate in the Wisconsin DNR's Citizen Lake Monitoring Network. For almost 30 years, Bear Lake volunteers have gathered data on the lake's water clarity, temperature, and chemistry. These data are a valuable tool to assess the health of the Bear Lake ecosystem and detect changes occurring over time.
Once a month, volunteers lead by Bob and Dorothy Moe boat out to the "Deep Hole" (the deepest part of Bear Lake) and take secchi disk readings (water clarity), record lake temperature at different depths, note observations about the lake's appearance and the presence of invasive species, and collect a sample of lake water for analysis. The DNR tests the water sample for the concentration of phosphorous and chlorophyll.
Phosphorous is a naturally-occurring chemical found in all waterbodies and anywhere plants grow. It is a major component of fertilizers, soaps, and sewage, so human activities can have a big impact on phosphorous levels. The concentration of phosphorous is important in lake management because it is food for plants and algae -- too much phosphorous can cause a lake to become eutrophic (roughly translated, "lots of food") which is characterized by algae blooms, decreased oxygen available for fish, and other problems. The concentration of chlorophyll is an indirect way to measure the amount of plant-matter and algae present in the lake.
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| Getting the sample ready to ship to WI DNR |
Click here to view a presentation about Bear Lake's water quality given at the June 2022 annual meeting. Click here to view the time-series video of dissolved oxygen and temperature vs. depth at the Deep Hole.
Water quality can change over several time scales including throughout a given day and over many years. Out of curiosity, we evaluated how dissolved oxygen (DO) and temperature vary over the course of 24 hours by conducting DO and temperature profiles at the Deep Hole, taking a reading every hour for 24 hours. Click here for the 24-hour DO profile. Click here for the 24-hour temperature profile. Click here for data in graphical form. The data was shared with Paul Skawinski, UWSP / Extension Lakes, who had the following comments;
The DO variation is simply explained by the oxygen-holding capacity at higher temperatures. As the water warmed, the DO concentrations went down because the water was oxygen-saturated and warm water can hold less oxygen than cooler water.
Some of the other gradual changes in DO over the 24 hrs are likely due to migration of photosynthetic organisms and/or zooplankton communities. The photosynthetic organisms would have a positive effect on the DO level, and the zooplankton would have a negative effect on DO concentrations. They move to different water depths throughout the day to seek out an ideal temperature, light intensity, food, etc.
The spikes in DO and temperature above and within the thermocline is interesting... If the wind shifted/strengthened, maybe the lake experienced a shift in thermocline height as the surface water was pushed to one end of the lake (lowering the thermocline) and the thermocline rose on the opposite side.
Current water quality data can be found here,
If you're interested in helping out with the Association's Lake Monitoring efforts, please contact our resident citizen-scientists, Bob and Dorothy Moe at 234-7095.