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 madison.com website.

Muckraking Mendota: Let’s Just Be Friends

UW undergrad, Emily Hilts, spent her summer getting to know Lake Mendota. While she didn’t fall head over heels for Madison’s lakes, she’s leaving on good terms.

by Emily Hilts

This morning, I moved my books and papers out of the desk I used at the Center for Limnology all summer, and took some time to reflect on what I’ve learned about Lake Mendota after three months of snorkeling, paddling, boating and exploring its shores. Thinking about the goals I set for myself, I realized that the out-of-work experiences I never shared in this blog taught me just as much about the lake as all of my naturalist-inclined explanations of its flora, fauna, geology and ecology.

In June, I was charting my way around Lake Mendota, searching for stories.

The purpose of this blog was twofold. First of all, I wanted to share my discoveries about Lake Mendota with my readers. At some basic level I think it’s safe to say I’ve accomplished that. But, in hindsight, that’s not really what I cared about.

I realized this after a morning of fishing with Jim Bruins, who was a UW zoology undergrad and a project supervisor at the Center for Limnology in the mid 1960s. After three summers with the department, it was time to at least learn how to catch a fish on a line, and I can hardly think of a better person to teach me than Jim. It wasn’t necessarily that he shared a wealth of technical information – we were just bobbing for bass and perch – but he was a library of stories about Madison and Lake Mendota. He told me about how the cisco used to be so abundant, he and some buddies could dip-net them out of the water when they came in to spawn. He knew where bass used to be easily caught, and how perch cycle between good and bad years. Read Emily’s final thoughts on life on Madison’s lakes –>

To read the full series of Emily’s work, visit The Life Aquatic, the blog for the lab of Dr. Jake Vander Zanden.

Muckraking Mendota: Mouthing Off (with Fish)

Last fall, as I moved in to a new house, I asked my parents (who are regular patrons of rummage sales) to look for a taxidermied fish. When they scrounged up a musky, with its mouth wide open to reveal pointy teeth, I was ecstatic. My roommates were less enthusiastic – one even claimed to feel nauseous at the mere sight of it.

 What's not to love about fish (and their mouths?) Photo: Serendigity via Flickr


What’s not to love about fish (and their mouths?) Photo: Serendigity via Flickr

I could understand why my roomies didn’t want it in our living room, but their negative comments about fish were rather discouraging – one said she thinks fish are simply gross. As much as I love looking at fish, it can be hard to convince others that they’re worth appreciating. Of course that doesn’t mean I’m not going to try! Keep reading –>

Muckraking Mendota: What Do We Mean By “Clean?”

by Emily Hilts

Trout-Lake-July-2012-6When I worked at Trout Lake Station, I usually went running after a day in the field and then jumped in the lake – not only to cool off but to get clean. After all, Trout Lake is gorgeously clear, and the stink of the day washed right off. Showers were reserved for a couple of times in the week, before seminars or going into town. My sister (who, at one point, showered twice each day during the summer) was endlessly frustrated with this habit, and grew more worried as the summer passed that I was really becoming a hippie. She tried many times to explain to me what it meant to be “clean,” a definition that you’d expect would be quite simple but, in reality, is surprisingly complex.

In last week’s post, I explained that lakes don’t all look the same, and what’s “normal” in one water body may not be what’s right for another.  So that begs the question, what does it mean for a lake to be “clean?” Keep reading –>

Muckraking Mendota: The Water/Land Interface

by Emily Hilts

Willow Creek, part of the Lakeshore Nature Preserve is a hotspot for wildlife. Photo: E. Hilts

Willow Creek, part of the Lakeshore Nature Preserve is a hotspot for wildlife. Photo: E. Hilts

So far this summer, I’ve either stayed below the surface of Mendota’s waters or perched on top of the lake in a boat. Which means, of course, that I’ve been missing big pieces of the overall puzzle of this aquatic ecosystem. To fill in some of the gaps, it was time to head back toward land.

As the lakeshore path curves away from the Lakeshore Residence halls, it crosses a bridge where Lake Mendota and Willow Creek meet. The small bay is protected by a sandbar, but with this year’s high water levels, the only trace of its existence is a clump of willow and aspen that now appear to grow out of the water. Welcome to the wetlands. Shrubs creep out from shore, and their ancestors – now brush in the water – provide excellent fish habitat. Cattails extend out even further, accumulating silt with their roots. They create new ground under a few inches of water – a transition between lake and woods. Keep Reading –>