Sentinel lakes monitored for effects of climate change

Heading back to shore
The research team heads back to shore on Monday, Oct. 4, 2010, after collecting water and algae samples from Lake Carlos.
MPR Photo/Ann Arbor Miller

State and federal researchers are taking a very detailed look at some Minnesota lakes to monitor the effects of climate change and pollution.

The so-called super sentinel lakes that will act as an early detection system for poor conditions include Lake Carlos, near Alexandria, Elk Lake in Itasca State Park and Trout Lake in Cook County. Because of their cold deep water, the three lakes have been designated super sentinels.

There are a total of 24 sentinel lakes scattered across the state which are also monitored, but in less detail than the super sentinels.

Among the researchers visiting them is U.S. Geological Survey Hydrologist Richard Kiesling, who recently fired up a four-person fishing boat loaded with research gear. Pointing the boat into a 20-mile-per-hour wind, he headed onto Lake Carlos.

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"Carlos is an interesting lake because of its depth," Kiesling said. "It's 160 feet deep and that means it maintains fairly cold deep water through most of the summer."

Researchers want to know if the cold lake will warm because of climate change or increased pollution possibly threatening cold water fish species.

At the center of Lake Carlos, Kiesling circled a bright, bouncing orange buoy that is anchored to the bottom by a line that holds dozens of temperature probes. They took the lake's temperature every 15 minutes from the top to the bottom 160 feet below. When the probes are pulled up, the data is recorded and will be downloaded to a computer.

Preparing a sampler
Emily Resseger, a hydrologic technician with U.S. Geological Survey and a master's student at the University of Minnesota, prepares a sampler on Lake Carlos on Monday, Oct. 4, 2010. The device will be rinsed in lake water multiple times before an actual sample of lake water is collected for study.
MPR Photo/Ann Arbor Miller

Fighting the wind, Kiesling dropped a plastic tube in the water to collect a sample.

Researchers collect samples from the surface and about 60 feet down in colder water. They also collect samples of the lakes tiniest residents, algae and zooplankton. They are monitoring in detail the temperature, oxygen, water chemistry, nutrients, and algae production.

All of that detailed data will go into a computer model that will let researchers predict how the lake might change in the future. Will warmer water affect the food supply for fish? Will less oxygen in the water kill some fish species?

Kiesling said there's already evidence climate change affects how long lakes are ice covered.

Emily Resseger
Emily Resseger, a hydrologic technician with U.S. Geological Survey and a master's student at the University of Minnesota, adjusts the lid on a sample of algae from Lake Carlos on Monday, Oct. 4, 2010.
MPR Photo/Ann Arbor Miller

"We'll have ice setting up later in the fall and ice going out earlier in the spring," he said. "How is that going to change our expectation of the way the lake behaves? It probably will be something different than we're used to. The models will help us answer the question of just how noticeable that change will be and just how extreme that change will be."

Understanding how a lake might change in the future could be important for resource managers like the state Department of Natural Resources.

Sentinel Lakes Coordinator Ray Valley said it's clear the range of some fish species will change as lakes warm. Some cold water species might disappear. Other species might be less affected by changes in water temperature and oxygen levels. Valley said using a computer model to predict what will happen will allow DNR officials to be make adjustments as the lake changes, instead of waiting until after those changes take effect.

"We need that information to know what lakes are going to not make it -- regardless of what we do on the landscape -- because they're just going to be too warm," he said.

Water quality equipment
Emily Resseger, left, and Sarah Elliott, right, prepare documentation and an instrument called a sonde to measure water quality in Lake Carlos on Monday, Oct. 4, 2010.
MPR Photo/Ann Arbor Miller

Researchers also want to know which lakes have the potential to be resilient so they can consider focusing conservation efforts on those lakes, he said.

Another critical aspect of the Sentinel Lakes project is sustained long term data collection. Over time, a lot of data has been collected about Minnesota lakes. But it's usually for a specific project. When that project is finished, the data collection stops.

Valley said collecting the same data over decades lets researchers actually see cause and effect play out.

"And we don't know how long that is in some cases," he said. "That only becomes apparent after many years of monitoring. That's why this has got to continue on. The main benefits will come with long-term monitoring."

Hydrologist Richard Kiesling
Hydrologist Richard Kiesling holds a sample of algae from Lake Carlos on Monday, Oct. 4, 2010. The lake, located five miles north of Alexandria, Minn., is one of 24 Minnesota lakes being studied as part of the Sentinel Lakes Project.
MPR Photo/Ann Arbor Miller

The Sentinel Lakes project is funded by a three-year grant from state lottery proceeds.

Valley said his big challenge is to ensure long-term funding for a project to monitor the health of Minnesota lakes through what he said will be one of the greatest periods of environmental change in recent history.

For more information on the sentinel lakes, visit