AUBURN — Diver Jackie Bailey bubbles to the surface of the murky pond water and passes a fat mesh bag of leaves and fronds to the waiting boat.

She’s checking on the status of the bottom of the pond known as the Basin just north of Lake Auburn, and she’s pleased with what she’s seeing underwater.

Her efforts and those of the Lake Auburn Watershed Protection Commission to keep out milfoil and other nonnative plants seem to be paying off — in this area, at least.

“It seems to be working,” she said. “It’s not as bad as in some other places.”

Water-quality officials in Maine are on constant watch for nonnative plants, especially variable leaf milfoil. That’s a nonnative nuisance perfectly suited for life in Maine’s ponds, said Water Quality Manager Mary Jane Dillingham of the Auburn Water District. Nothing natural in Maine can keep it in check, which means it spreads and spreads.

“When you have this plant taking over, it affects the entire ecosystem and all the plants that clean the water just can’t compete,” Dillingham said. “The milfoil is very prolific. It grows in clumps and it just takes over, dumping a lot of organic matter into the water.”

That’s what’s happened in the Basin, where the plant grows in thick, fuzzy ropes. It’s what Dillingham and Bailey are trying to keep from happening in Lake Auburn. A few plants have been found in the northern part of Lake Auburn, and Dillingham hopes to keep them from spreading.

“Prevention is really the best tool we have,” Dillingham said. “Of course, we can’t use herbicides because that’s our drinking water, so we use other methods.”

Water-quality officials suspect the plant is spreading from lake to lake in Maine via the bottoms of recreation boats and fishing equipment. As of March 2011, the nuisance was growing in 30 Maine lakes and ponds, including Lake Auburn.

In other Maine lakes, specialized underwater vacuums are used to suck up milfoil, from tip to root. In the Basin, divers pluck the plants from the ground — basically, weeding underwater.

“You know those plants in your yard that grow everywhere and they just keep coming when you pull roots? Milfoil is like that,” Dillingham said.

The plant’s stalks are especially fragile, which makes them spread more easily.

“One tip can break off and float away and start a stand of its own, somewhere downstream,” Dillingham said. “That’s why we don’t allow motorboats in the Basin. They just break up the plants and spread them around.”

The other solution is to blot out the sun from the lake bottom. Water-quality officials have spread a synthetic fabric, called a benthic barrier, across parts of the pond’s floor since 2002. By darkening the floor, they starve all of the aquatic plants of sunlight.

It’s worked in spots around the Basin, where the water is glassy compared to the rest of the pond. Not even native lilies can be found there.

That raises another problem, Dillingham said: Lake areas with no plants are a perfect haven for milfoil to take root.

“But we’re learning more and more about what to do,” Dillingham said. Bailey, who is working on her Ph.D. in aquatic biology, studying invasive plant species at the University of Maine in Orono, said she’s keeping track of the conditions in the Basin and at several other Maine lakes. What they learn here could help control the plant everywhere.

“And what we’re seeing is working,” she said. “We’re not seeing it in the same size or abundance that we once did. Now we’re getting to the nit-picky stage. That’s harder, but it’s good.”

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