Lake Mendota: A Scientific Biography

How did we miss this excellent feature on Lake Mendota and the CFL? We have no idea, but better late than never – enjoy!

By: Masarah Van Eyck

Steve Carpenter. ©UW-Madison University Communications  Photo by: Jeff Miller

Steve Carpenter.
©UW-Madison University Communications
Photo by: Jeff Miller

From the window of his second-story office overlooking Lake Mendota, Steve Carpenter can see the UW rowing team running drills. On a warmer day, he might glimpse yellow-hulled “tech” boats, piloted by amateur sailors, lurching around the buoys. And on an early autumn morning, a lone paddler might suggest the image of a traveller from long ago, navigating the waters in a birchbark canoe.

Like all lakes, this one holds the past, present and even the future in its depths.

“Lakes reflect the land around them,” Carpenter says. “They also reflect the ways that humans use that land, and the ways we use the water.”

Often called “the most studied lake in the world,” Mendota is the birthplace of the field of limnology, the scientific study of inland waters. Thanks to a trove of long-term data gathered over more than 100 years by UW scientists like Steve Carpenter, the connection between Mendota and the humans who have interacted with it over time is unusually well understood.

This data offers a glimpse of the lake’s future — one that Carpenter and his colleagues are eager for us to realize that we are responsible for writing. Continue reading here –>

Awards, Judges Set for “Our Waters, Our Future” Writing Contest

MADISON — Two of Wisconsin’s literary leaders will help decide the winner of the Our Waters, Our Future writing contest. Peter Annin, journalist and author of Great Lakes Water Wars, and Fabu, as Madison’s third poet laureate is professionally known, have agreed to help select the top stories that imagine a positive future for water and people in south-central Wisconsin.

What is your vision for the future of Madison's lakes? Image:

What is your vision for the future of Madison’s lakes? Image:

The contest encourages Wisconsinites to envision a desirable future and participate in building that future through storytelling. Representatives from Madison Magazine, which will publish the winning story, will also be part of the judges’ panel.

Peter Annin. Photo: Northland College

Peter Annin. Photo: Northland College

“We are leaving the century of oil and entering the century of water, which means water will become the most important natural resource in the world by 2100. Communication—especially writing—can play a key role in helping people understand just how important water is becoming on a regional, national and international level,” says Annin, who is also the co-director of the Mary Griggs Burke Center for Freshwater Innovation at Northland College.

Originally from the southern United States, Fabu draws on her connection with the Mississippi River, which she says has “watered [her] both historically and creatively.”



“I felt at home in Wisconsin when I saw the Mississippi River in La Crosse. It has been a pleasant discovery learning about the various waters in Wisconsin. Our Waters, Our Future speaks to the importance of this resource, and I am excited to read what writers say about this topic,” says Fabu, who served as Madison’s poet laureate from 2008 to 2012.

Several local businesses specializing in outdoor recreation have offered their support of the contest as awards sponsors for the winner and top finalists, including Fontana Sports Specialists, Brittingham & Wingra Boats, Rutabaga Sports and REI. Local artist John Miller, whose work often features water, will also create an illustration for the winning story.

The contest seeks short stories that are solutions-oriented and, while fictional, are also scientifically plausible. Stories should take place in the year 2070 and in the region around the Yahara Watershed and/or the affiliated counties of Dane, Rock and Columbia.

Despite this regional focus, the contest is open to all Wisconsin residents and students 18 years or older. Since the region contains the state’s capital and flagship university, thousands of acres of productive farmland and valuable water resources, including the Yahara river and lakes, the issues it faces have statewide significance.

The deadline to submit stories is February 1, 2016. Complete contest details can be found at

The contest is a collaborative effort by the University of Wisconsin-Madison’s Water Sustainability and Climate project and Center for Limnology, Madison Magazine, Sustain Dane and the Wisconsin Academy and Sciences, Arts & Letters.


CONTACTS: Peter Annin,, 715-682-1360; Fabu,, 608-235-4745; Jenny Seifert,, 608-512-6259



It’s Spring 2016! Help Us Monitor Mendota’s Clear-Water Phase

Last year at this time, we asked you to help us monitor Lake Mendota, as we worried that we’d missed its “clear-water” window. We’re happy to report that, in 2016, we’re nearing a 6 meter Secchi depth and seeing lots of daphnia in our nets. Will this be a clear spring for Madison’s lakes? Stay tuned. Until then, enjoy this post from last year! And feel free to help us #MonitorMendota!


by Jake Walsh, May 20, 2015

Spiny water flea under the microscope. Photo: Jake Walsh

Spiny water flea under the microscope. Photo: Jake Walsh

We’ve written before about how an invasive zooplankton called Bythotrephes longimanus, or “the spiny water flea” (SWF) is eating our native algae-grazing friends, the tiny crustaceans called Daphnia.

This is important because, as phosphorus pollution leads to algae blooms and lower water quality, we are also losing the critters that keep that algae at bay and give us our annual spring “clear-water” phase. 

Since SWF was first detected by a group of UW-Madison undergrads in Lake Mendota in 2009, we’ve lost over 80% of our Daphnia pulicaria (the big Daphnia that eat a ton of algae) and over 2 feet of water clarity in Lake Mendota.

Image: Jake Walsh

Daphnia abundance and Secchi depth before and after spiny water flea detected in Lake Mendota. Image: Jake Walsh

However, 2014 may have been the worst yet. The intensity of SWF predation on Daphnia in the fall of 2014 was twice as high as any other year we’ve observed. It was so bad that, on September 2nd of 2014, the voracious spiny water flea caused the collapse of Lake Mendota’s Daphnia community and they still haven’t recovered as of today.  Where I used to pull in hundreds of thousands of Daphnia pulicaria in a single sample, I’m now often only finding a single tiny individual in my net.

If you love clear water, then these little Daphnia pulicaria are your best friend! Are we losing them in Lake Mendota?

If you love clear water, then these little Daphnia pulicaria are your best friend! Are we losing them in Lake Mendota?

While we’ve seen “tough times” for Daphnia before, we’ve never witnessed anything like this in the four decades the Center for Limnology and Long-Term Ecological Research (LTER) scientists have monitored Lake Mendota.

As a result, water clarity in Lake Mendota has been downright dismal this year while Lake Monona, which doesn’t have a large SWF population, is looking nice and clear. In fact, last year’s average water clarity was BETTER in Monona than Mendota for the first time since we’ve been keeping records. Continue reading

Fish Fry Day Video: Ice Fishing in Madison, Wisconsin

Andrew Stevens is a graduate student working on a master’s degree both with Pete McIntyre in Freshwater and Marine Sciences as well as the Water Resources Management Program here at UW-Madison. He’s also an avid ice angler and handy with a camera. We asked for a Fish Fry Day special – and Andy delivered. Enjoy!

Steven’s focus has been on northern pike spawning habitat restoration and his research at the Center for Limnology focuses on mercury in white suckers and also fish consumption advisory outreach to minority angler groups. Well, that and capturing amazing footage from beneath our lakes’ icy winter cover.

Algae Blooms in Fall Mean Lake Mendota Is Mixed Up

A mid-October algae bloom shows up on the Lake Mendota shoreline. Photo: Sam Oliver

A mid-October algae bloom shows up on the Lake Mendota shoreline. Photo: Sam Oliver

Earlier this month, anyone down on the shores of Madison’s lakes may have noticed the water tinged the green hue of an algae bloom, something we normally associate with the warmer summer months. But a final fall bloom isn’t all that unusual – It just means that the lakes are, literally, all mixed up.

During the summer our lakes stratify, meaning that a warm upper layer of water forms and settles on top of the denser, colder water below. Throughout this period, only that upper warm layer of water, or epilimnion, gets mixed up, bringing anything floating at the bottom of the layer to the surface and sending things at the top down. But nutrients that fall into the lower, colder layer of water, the hypolimnion, are trapped and begin to build up over time.

When the weather (and the lake) begins to cool, the lake enters a phase called “turnover.” During turnover, the epilimnion cools off, grows denser and pushes into the hypolimnion, shrinking that cold, bottom layer and bringing whatever is in it back into the mixing cycle.

AN illustration of seasonal lake mixing and stratification. Image: National Geographic

AN illustration of seasonal lake mixing and stratification. Image: National Geographic

Eventually this upper layer cools to the temperature of the bottom layer and the entire lake mixes, bringing an upwelling of nutrients stored since late spring. And these nutrients act like a fertilizer, promoting the growth of anything green. Continue reading

Clear-Water Phase: Are We Missing Lake Mendota’s Window?

Lake Monona's already doing it, why aren't Mendota's waters this clear? Photo: A. Hinterthuer

Lake Monona’s already doing it, why aren’t Mendota’s waters this clear? Photo: A. Hinterthuer

Over the last two weeks, Lake Monona, Lake Waubesa, and Lake Kegonsa have all entered into their annual rite of spring’s clear-water phase. Lake Mendota, however, remains a murky mystery. Why are the downstream Yahara lakes so clear, when the lake at the top of the chain isn’t? Perhaps more important, are we going to miss Mendota’s clear-water window this year?

Not necessarily, says Ted Bier, research specialist for the North Temperate Lakes Long-Term Ecological Research program. “Mendota was right on the cusp of moving into a clear-water phase over Memorial Day weekend,” Bier says. “But then it got slammed by that last storm.”

If you need a refresher (or aren”t here in Madison) that storm dumped 1 to 2 inches of rain on our fair city in a two-hour span. And all of that water ended up in our lakes, carrying sediments and nutrients that can cloud the water. Sediments can take several days to settle out to the bottom, especially if windy conditions keep them suspended, says Bier. And that sudden influx of nutrients can cause algal blooms.

People around the lake have been noticing. My office, for example, usually affords me a view of carp congregating just off shore for their annual spawning run (million-dollar view, I know). This year, all I can see are ripples on the green surface. The Clean Lakes Alliance recently shared a picture one of their members took of a greenish brown boat wake in Mendota – the result of algae being churned up to the surface by its propellers. Continue reading

Save the Date! Hasler Lab 2014 Open House

Modern limnology in North America was born right here at the University of Wisconsin-Madison. Today, scientists from across Wisconsin, the nation. and the globe are doing world-class freshwater research right on the shore of Lake Mendota – exploring issues like invasive species, sport fish dynamics and algae blooms.

On Friday, June 20th, from 2pm to 6pm, the Center for Limnology will open the doors of Hasler Lab for a “behind the scenes” tour of the science of freshwater research! You’re invited to come see how the research conducted at the CFL is being used to better understand, protect and improve Wisconsin’s lakes, rivers and streams.

Visitors board the Limnos for a "research cruise" on Lake Mendota.

Spend a half hour or the whole afternoon talking with scientists, getting your hands wet and learning what it means to study lakes for a living. Visitors will board our research vessel, the Limnos*, for a ride out onto Lake Mendota to try their hand at using various lake research tools. Continue reading

Spring Has Sprung in Wisconsin’s Waters

It’s official! Not even highs in the low 40’s and a couple of overnight snow showers could stop it – spring has arrived in Madison. According to the Wisconsin state climatologist, Lyle Anderson (sorry, John Young!), Lake Mendota was free of ice on April 12th, right on the heels of the thaw of other Madison lakes Monona (April 10th) and Wingra (April 9th).

Yet another snow shower couldn't stop Lake Mendota from thawing and common loons from coming back. Photo: Hinterthuer

Yet another snow shower couldn’t stop Lake Mendota from thawing and common loons from coming back. Photo: Hinterthuer

Although the daily highs have been nothing to write home about, strong winds really did the trick, keeping the surface too choppy for ice to refreeze during nightly lows. The April 12th thaw date is only one day later than last year, but ranks as the latest ice off date since 1979.

All told, Lake Mendota was ice-covered for 117 days this year, a boon for anyone who loves to ice fish, ice skate, cross country ski, or kite board across the snowy surface. This year’s date would be considered “nearly late” in the records. In 1857, Continue reading

Past Post: Early “Spring Cleaning” for Lake Mendota

Obviously Lake Mendota is still frozen over here in the Spring of 2014. But, two years ago, Madison lakes had officially opened up (i.e. thawed) on March 10th and, by early April, we were writing what proved to be one of the most popular posts in CFL blog history. Since we’ve been dreaming of spring since mid-February, here’s a post from the archives explaining why crystal clear water means a lake is teeming with life. Enjoy. And, never fear – spring cleaning is coming for Madison lakes even in 2014. Promise.

Madison Lakes Have an Early “Spring Cleaning”

Posted on April 18, 2012 by admin

The view along the Mendota shoreline shows the lake in its Spring "clear water" phase Photo: Adam Hinterthuer

If you head down to the shore of Lake Mendota today, you’ll notice you can see right down to the bottom. In fact, the current Secchi reading is seven meters, meaning you can get a clear view of Lake Mendota’s depths more than 20 feet down.

At first glance, it might seem that there’s just not much going on down there, but Lake Mendota is actually teeming with life and right in the middle of an algae bloom.

So what gives on the clear water?

The secret to our currently crystal-clear lake is a tiny zooplankton called Daphnia pulicaria.

While conditions are ideal for some species of algae, like fast-growing diatoms, to thrive, the current cool, highly-oxygenated water is also perfect for Daphnia pulicaria, which are voracious grazers of these kinds of algae. Continue reading

Thickest Lake Ice in Decades May Last Into Spring

Ted Bier, our senior research specialist for the Long-Term Ecological Research program, was recently photographed on Lake Monona holding this massive chunk of ice in front of the Madison skyline.

Ted Bier hoists a two-foot thick chunk of ice on Lake Monona. Photo: Kirsten Rhude

Ted Bier hoists a two-foot thick chunk of ice on Lake Monona. Photo: Dave Harring

That picture led to the following story on The Capital Times website:

How thick is the ice on Madison’s lakes? Researcher Ted Bier almost didn’t have enough drill to find out this week.

Bier takes ice depth samples as part of his work for the UW-Madison Center for Limnology, and he was out in the middle of Lake Monona on Thursday to get a reading. The drill kept going and going until finally reaching water underneath the ice.

When they extracted the ice core that you can see in the photo above, the depth measured 65 centimeters, more than 25 inches.

“Generally speaking, all the lakes in the area had 2 feet or more of ice on them at some point in time this winter,” Bier said. “That’s 40 to 50 percent thicker than we usually have. I’ve been here 13 years and it’s the thickest I’ve ever seen.” – Read the rest on the website.