Ber Juan Lake in Rolla's Ber Juan Park has three small floating islands in the middle. They aren't big — each one is about 6 feet in diameter, and they look small compared to the 2½-acre lake.
But these floating wetlands are part of an initiative to keep bodies of water in Missouri healthy in a natural, low-cost way.
Ber Juan Lake is pretty urban, as much as anything can be in a town of 20,000 people. It's surrounded by the city's rec center, an outdoor pool, soccer and baseball fields and a disc golf course.
Still, this little oasis has a fair amount of nature in and around it, but it needs help.
"This time last year, it was completely green out here," said Andy Smith, recreation manager in Rolla's parks department.
Every year, the lake becomes choked with algae and other unpleasant stuff because it is mostly fed by stormwater runoff carrying high levels of nitrogen and phosphorus, largely from fertilizers.
Rolla is the latest city to partner with the Missouri Department of Conservation on a cheap and easy way to naturally clean up the lake — floating wetlands.
The tiny islands are made of rubber-coated foam and covered in a collection of native plants. They float in the middle of the lake, anchored like a buoy. They are porous, so the plants' roots grow through them and into the lake.
"They're designed to allow wetlands to be built on top of surface water," said Blake Friedrich, a fisheries biologist with the Department of Conservation. "They trap nutrients, controlling phosphorus, nitrogen, while offering native pollinator habitat and habitat for birds and other things like that out on what would be considered just open flat water."
It costs about $3,000 to get one of these floating wetlands into operation. They start with solar-powered water pumps on board for about a month until the roots grow through the island and can reach the lake water. There is minimal maintenance after the islands are established.
Ber Juan Lake has three of them this summer, with three more set to be put out next year and a final trio in 2028. That number came from some pretty serious data.
Scientists at Missouri University of Science and Technology ran tests and a pilot project to figure out exactly how many were needed to clean up the lake.
"You need to get a lake to about 0.2% coverage in floating wetlands to see a drastic reduction in nutrient load in these lakes," Friedrich said. "Because their roots are not limited by soil, these roots can grow to be 7 feet long once these plants get established, and they can grow really high."
The department and Missouri S&T estimate that about 250 square feet of these floating wetlands is equal to one actual acre of native wetland left in the wild.
The floating wetlands are also more efficient because the native plants are protected from animals, people and weeds that could interfere with them if they were on land, adjacent to the lake.
The low-cost and natural solutions don't stop there. A problem floating wetlands face is that geese think they are a pretty cool place to land, eat and nest — and that kills the plants. The solution is a bunch of twigs.
"We actually place sticks on top of them because they do not like uneven surfaces on their feet," said Nick Lamey, another fisheries biologist with the department. "It's just uncomfortable, kind of like us stepping on Legos in the morning that kids leave out."
The floating wetlands are working in Rolla. The city hasn't had to use its usual chemical treatments to reduce algae, and each one of those can cost $1,000.
"These are clearing it up and kind of cutting away all that. And I've noticed a lot more people down here fishing this summer and just kind of being around the lake," said Andy Smith of the parks department.
The goal is to have a healthier lake that also attracts people to use the park. That's hard to do when it's filled with green muck.
"People want to see these lakes nice and fishable and enjoy them. I love bringing my own daughter down here to catch fish. That's what we did for Father's Day this year. We came down here, and she was catching little 4-inch bluegill and had an absolute blast," Friedrich said.
The floating wetland project from the Missouri Department of Conservation is about five years old. The agency has placed dozens of floating wetlands in state-owned lakes and worked with cities, including Rolla. It also provides advice to private property owners who may want to put floating wetlands on their own lakes and ponds.
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