In recent times, environmentalists and scientists have spent a lot of energy cleaning the Lake Michigan watershed, especially the Milwaukee River.
Pollutants have made their way into it locally and miles upstream, eventually flowing into the lake, impacting the quality of its water.
But you might be surprised to learn that scientists have been dipping into problems in Madison’s Lake Mendota since the 19th century, long before attention was focused here.
WUWM Environmental Reporter Susan Bence met two scientists who lead today’s research on Mendota.
It’s hard to believe Steve Carpenter is a serious scientist.
He heads UW’s Center for Limnology – that means the study of freshwater systems. But the white-bearded ecologist appears to be having too much fun.
“If you feel uneasy, just look at the horizon,” Carpenter says.
We’re cruising out onto a windy Lake Mendota on The Limnos, a 30-foot research vessel that’s been in service here for almost a half-century.
Carpenter is bundled in a windbreaker and life preserver, and can hardly wait to fill us in on his research. But he waits until the anchor is cast and our legs steady.
“This lake, Lake Mendota is often been called the most studied lake in the world. Limnology in North America started here in the 1880s,” Carpenter says.
Carpenter pulls out a traditional tool limnologists use - a Secchi Disk.
“Secchi was the captain of the pope’s yacht in the 1800s. He invented this thing and went around the Adriatic Sea and other parts of the Mediterranean recording water clarity,” Carpenter says.
The weighted plastic disk measures eight inches and is painted with alternating black and white quadrants. The contraption’s attached to a long rope.
“So what I’m going to do is drop this thing overboard. The idea is to let it down until you can’t see it anymore. Alright, that’s three-and-a-half meters which is actually pretty good,” Carpenter says.
But compare that clarity with Mendota’s condition around 1830.
“When Madison was first settled, this lake was very clear and you could see the bottom in 30 or 40 feet of water.,” Carpenter says.
Conditions began changing as settlers plowed the prairies and soil ran into the lake. Carpenter says water quality continued to decline right through the World War II era.
“We had a lot of gunpowder factories and it turns out that the technology for making gunpowder is exactly the technology you need to make fertilizer,” Carpenter says.
Ammonium nitrate to be exact.
Factories transitioned from producing gunpowder, to pumping out fertilizer. Phosphorus was added to the brew to make it more “nutrient rich.” Carpenter says farmers were using a lot of it.
“And it ran off and got into the lakes,” Carpenter says.
Next, he says, Madison grew.
"And there was a lot of development and there was no sewage treatment, so raw sewage was being dumped into the lake. A committee was formed to deal with the problem and eventually they agreed on a taxing plan for cleaning up the lake and by 1971 all the sewage was diverted from this lake, " Carpenter says.
Carpenter says people thought, no sewage would equal a clean lake. But 10 years later, the water quality had not improved at all. He says Lake Mendota smelled nasty and was filled with blue-green algae. It’s toxic when it blooms and can destroy a lake if not controlled.
“In about 1981, the first non-point pollution program in Wisconsin’s history started in this watershed to try to clean up this lake and it completely failed,” Carpenter says.
Farmers ignored the plan because they weren’t given any incentives to change their ways. While people in Madison were frantically trying to figure out what to try next, Carpenter and colleague Jim Kitchell were successfully controlling noxious algae in small lakes in Northern Wisconsin. Kitchell says they came up with a different approach - using fish to reduce algae problems.
“Changing the way food web interactions work. We move fish around. Under some configurations, large Daphnia, large means two millimeters, came to be very abundant,” Kitchell says.
The zoologist calls the tiny crustaceans “small sumo wrestlers” who eat everything in sight, and are especially fond of the algae that muck up water systems. The DNR called on the two scientists to tackle Lake Mendota’s problems.
Over a three-year period, Carpenter and Kitchell stocked the lake with prescribed numbers of walleye and northern pike and its ecosystem seemed to respond beautifully.
“That year we had no blue-green bloom. There were places out here were you could see the bottom in 35 feet of water,” Kitchell says.
That doesn’t mean Mendota is problem-free.
A few weeks ago, researchers spotted an invasive critter in the lake, and unfortunately, one that eats the little sumo wrestlers. S
teve Carpenter says, if the invader’s population grows, there’s nothing much his team can do but watch.
Maybe it’s in these kinds of situations that Carpenter’s positive attitude pays off.
Although brilliant scientists like him have been tackling Mendota’s problems for more than 120 years, there will probably always be new ones.
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