Sickness In the Water
James Johnson studies whole-lake treatments for the DNR

By Sara Specht

A cancer is invading Minnesota’s lakes, an aggressive campaign by foreign plants to occupy and take over whole bodies of water. So that would make James Johnson, graduate student in CFANS’s interdisciplinary Water Resource Sciences program, the lake doctor.

CFANS graduate student James Johnson is testing chemical treatments on invasive plant species in Minnesota lakes.

Johnson, 35, leads a Department of Natural Resources (DNR)-funded research project testing whole-lake, low-dose herbicide treatments for curlyleaf pondweed, which has been conquering lakes across the state. Like Eurasian watermilfoil, it grows densely and hampers boating and swimming, overwhelms native species and simply looks bad. Conventional control tactics haven’t made an impact on these invasive species.

“The whole-basin treatments are a big sledgehammer technique to pound it into submission, like chemotherapy for lakes,” Johnson explained. “But is it something that’s logically feasible? Can you put this stuff in and there’s some wiggle room? Or is it hard to do this in an effective way, and you’re just killing the patient every time you treat them?”

The treatment in Johnson’s case consists of two chemicals, tested on three lakes apiece, with an additional three control lakes receiving no treatment for their curlyleaf plague. One chemical, fluridone, mixes in small dosages throughout a lake for an entire season and slowly prevents plants from reproducing, killing by virtually bleaching them out. The other chemical, endothol, is a spot treatment that only requires a few days’ contact time and can be used early in the season before native species begin to grow.

Unlike most native plants, curlyleaf begins growing in the fall, lying dormant under winter ice, to shoot to the surface as soon as the ice melts. Johnson hits the water in April just after the ice thaws for initial measurements, then again in June at curlyleaf’s peak. Finally, in August after curlyleaf dissipates, he assesses any effects treatment has had on native plants.

After two years, Johnson says the changes he’s seen in the lakes have been remarkable, knocking out the infestation much of the time. However, Johnson’s adviser, Ray Newman, a professor in the Department of Fisheries, Wildlife and Conservation Biology, is researching the curlyleaf’s chief reproductive tools—called turions—and finding that they can lie dormant in a lake’s sediment for years and remain viable. To Johnson, this suggests that these treatments may only be the beginning.

“It’s like pushing that ball below water, and it just keeps coming back up, and we just try to keep it under a little bit longer,” he says. “Hopefully this will get it down to a level where we can use the lakes again, the fisheries can come back, and we can get back a sense of an intact ecology. Then we can apply some other management tactics to keep it that way.”

Johnson plans to build on his research with the DNR after graduating in spring 2008 by consulting on management plans for Minnesota lakes, including some of those affected by his study. Bridging the gap between environmental engineering and biology in the Water Resource Sciences program, he says, has given him a key perspective to build a career in keeping lakes beautiful and healthy.