WINDHAM – Forest Lake – bordered by Gray, Windham and Cumberland – has a milfoil infestation. But, due to current environmental law, it’s a problem lake monitors are powerless to control.

Unlike other water bodies in the Lakes Region that are battling invasive, foreign plant invaders such as Eurasian or variable-leaf milfoil, a native, federally protected type of milfoil is growing with gusto all over Forest Lake, confounding experts and frustrating residents and boaters.

In summer 2007, the Forest Lake Association first noticed a new outcropping of plant growth in a cove on the lake. Originally misidentified as bladderwort, the colony started spreading, and now can be seen floating on the water as well as taking root in areas as deep as 12-14 feet throughout the shallow lake. The presence of the quickly spreading milfoil has lake association members concerned, since the heavy presence of vegetation in the lake has the potential to create algae blooms, which can limit oxygen levels in a lake and kill fish.

“Forest Lake is almost entirely in the littoral zone (the region of a lake where sunlight can penetrate to allow plant growth). Because of that this lake is very susceptible to invasive plant growth,” said lake association president Karen Hall. “And even though they say this is a native, it’s behaving as an invasive and has the potential of taking over the whole lake.”

This summer, the association learned what was first believed to be bladderwort is actually low-water milfoil, protected by the federal Natural Resources Protection Act because it is considered native to New England. Independent agencies at the universities of Connecticut and Michigan performed DNA testing on the samples this summer and fall and confirmed the species as native milfoil.

With the DNA confirmations, the lake association is powerless to prevent the plant from spreading. According to John McPhedran, biologist with the Maine Department of Environmental Protection, eradication efforts of a native species are forbidden by the federal Natural Resources Protection Act. Boat owners, however, are allowed to cut a 10-foot swath from their dock to open water.

That is little comfort to association members. At 198 acres, Forest Lake is considered a small lake, and since it is shallow – the deepest part being 34 feet, with most of the lake between 10-20 feet deep – boaters’ ability to cut a swath to deeper water where milfoil couldn’t grow would be little consolation, Hall said.

Hall also said the association’s efforts to restore health to the lake and keep out invasive plants has actually backfired by allowing the native plant a chance to take root in deeper water.

“There’s a big irony here. In the past few years with the help of a couple grants, we’ve been cleaning up the lake, greatly increasing the clarity of the water. But it seems by doing that, we’ve allowed more sunlight to penetrate deeper, which is allowing this plant to thrive,” Hall said.

Hall and others in the association believe the low-water milfoil, originally thought to only grow in 2-4 feet of water, is acting more like an invasive type of milfoil.

“I was shocked when they said this is native. This is acting so unlike a native. Native plants don’t take over an area and kill everything else,” Hall said. “If it was a non-native, we’d have the support of the Maine DEP, money from (the federal Environmental Protection Agency), but because we’re dealing with a native, we’re told we have to leave it alone.”

To limit its spread, the association installed buoys demarcating the boundaries of the heaviest sections of low-water milfoil on the lake in June. This prevents boat motors from breaking off bits of the plant, which can then reroot elsewhere in the lake.

Although he’s never heard of a native milfoil spreading as rapidly and as deeply as it is in Forest Lake, McPhedran said native plants can sometimes act like invasive plants, depending on the habitat.

“There are actually six types of native milfoil to Maine. These natives can grow very densely. And it’s hard to predict what a plant is going to do. You may see fluctuations. Next year, for example, it may not be so thick,” McPhedran said.

That is what Bob Heyner, a founding member of the Forest Lake Association’s plant patrol, is hoping. Though frustrated with the native milfoil presence on the lake, he is more focused on keeping true invasive plants out.

“We’ve been working very, very hard keeping variable and Eurasian milfoil out of Forest Lake,” Heyner said. “My No. 1 concern is keeping the invasives out. That’s the real story here…And who knows, depending on the winter, this stuff (low- water milfoil) might die off and be a non-issue.”

Another plant patrol member, Ed Keenan, who has volunteered countless hours probing the depths of Forest Lake conducting plant surveys for the past few summers, traveled recently to Branch Pond by Bangor to investigate its low-water milfoil problem.

“They didn’t have it to the extent we have it. But we’re both concerned. This stuff is supposed to grow in 2-4 feet of water, but it’s growing in well over 10 feet of water,” Keenan said.

Due to the wind action on the lake, bits and pieces of the milfoil regularly float up onto people’s property and get stuck in the lake’s outlet in Gray, Keenan said. Keenan regularly removes “wheelbarrows full,” he said.

“We’re frustrated because it is a protected species acting like an invasive. We have several rocky outcroppings and coves full of the stuff, but the whole lake has a stake in what happens,” Keenan said.

Lake association president Karen Hall would like to see the law regulating native plants “re-addressed,” since Forest Lake’s experience with the low-water milfoil is similar to other lakes’ experience with invasive plants.

“There’s got to be some kind of recourse, possibly in redefining what is an ecosystem or something specific to our lake,” she said.

Hall also believes the word “native” shouldn’t apply, since the low-water milfoil was never observed in Forest Lake before 2007.

“We’ve been on this lake for years and years and no one has seen this plant before. So how can it be termed a native? It may be native to New England, but in terms of Forest Lake, we think it was probably transported here by a float plane or maybe even a loon a few years ago,” Hall said.

McPhedran said one means of recourse the association has is to apply for a case review with the state Department of Environmental Protection. The review would cost the lake association money, McPhedran said, but as reported in its fall/winter newsletter, “the (Forest) lake association as an organization and the board of trustees cannot and have no plans to collect money or take action for milfoil management.”

Hall said the association was discouraged by McPhedran to pursue a full case review.

“There’s one way around it, apply for a case manager, which might allow us to get a hearing to change the law. But John McPhedran didn’t think that we had a chance going down that road,” said Hall. “So, now, we’re kind of trapped in this place, where the current law isn’t necessarily best for either the lake’s overall health or the homeowners and boaters who live on the lake.”