Mike Smith spent most of his career as a diver with the Detroit Police Department recovering cars, guns, and sometimes bodies from the city’s murky rivers.
“It kind of set me up for the zero visibility, poor conditions—being comfortable,” he says.
Smith wasn’t always rescuing evidence from crime scenes. Once, he pulled up a 19th-century cannon, likely from the War of 1812, that now sits in a museum. Another time, he found a bronze statue, buried neck-deep in the Detroit River, stolen from a World War II memorial outside the city.
“All that led me to pulling weeds under water,” he says with a laugh.
Now, Smith works to clear invasive plants out of inland lakes using a 21-foot boat outfitted with a long vacuum tube. He dives along the lakebed, pulling plants by their roots and sending them up the shoot—a method called Diver Assisted Suction Harvesting, or DASH. “It sounds way cooler than pulling weeds,” he admits.
Business has been booming, he says. “This kind of blew up. Now we’re going as far as New Jersey working.”
Tending lake gardens
There’s a big demand for invasive plant removal in lakes because early detection and rapid response is the best way to beat a budding infestation, explains limnologist Erick Elgin with Michigan State University Extension.
“Eradication becomes a lot more difficult, if not impossible, once that plant is found throughout the lake,” he says.
When some invasive plants take hold they can grow up the water column and form a thick mat on the surface. That messes with a lake’s ecosystem by blocking sunlight for other life below. And it’s a nuisance for people.
“You’re not going to swim through that or fish in it or anything. It completely hinders recreation,” says Jo Latimore, an aquatic ecologist at MSU who works with lake communities across the state.
To get rid of these problem plants, lake managers will often use chemicals that target invasive species. But some plants are resistant to those chemicals.
Like one long, ropy plant called Eurasian watermilfoil that can breed with a native variety. On these hybrids, the chemicals don’t work.
And chemical treatment is only partially effective against another invasive—technically an algae— starry stonewort, named after the tiny sequin-like stars found among its brittle branches.
“You can get beds of it that are many feet thick and if you try to apply the algicide to it, it kills the top but doesn’t sink down as it should,” says Latimore.
The most effective chemical to treat starry stonewort is copper, which can be highly toxic, posing its own concerns, according to Latimore.
Many would prefer to avoid chemicals altogether and opt for treatments like DASH. “It's for lakes that don't want to introduce chemicals into their ecosystem. That’s what we’re here for,” Smith reiterates.
This management strategy has limits — it’s not feasible to combat an infestation that covers acres. But it can help keep new patches of invasives at bay.
And like weeding any garden, it requires upkeep year after year. “Most of the time you're not going to be able to completely eradicate an invasive species from a lake using DASH or probably any other technique,” says Eric Calabro with Michigan’s Department of Environment, Great Lakes, and Energy.
Next year, Smith will be removing invasives across Michigan lakes again with a second boat and a bigger crew. “We’re that busy,” he says.