CRWA in the News

Invasive weeds in river worry mayor

By Galen Moore, Daily News staff

Daily News Tribune, Monday, July 17, 2006

WALTHAM - It's summer again, a time when visitors come from afar to the cool waters of the Charles River. Mayor Jeannette A. McCarthy wants the state's help to keep them out.

The visitors she has in mind are two species of invasive weed that in the past have choked the portion of the river known as the Lakes District, between the Commonwealth Avenue bridge in Newton and the Moody Street dam in Waltham.

Between 1995 and 2000, a mechanical harvesting program reduced growth of water chestnuts and Eurasian milfoil that had clogged the slow-moving waters there.

Often carried into domestic waters on the bottoms of boats, such plants thrive in ecosystems that lack the natural predators of their native habitats. In the past they have grown thickly in the Lakes District, creating a nuisance to boaters and swimmers and stifling native plants and animals.

Now the plants are beginning to stage a resurgence, McCarthy said.

"It is crucial to fund the follow-up limited weed harvests suggested by DCR's environmental consultants to prevent the recurrence of the serious infestation of the past," McCarthy wrote to Department of Conservation and Recreation Commissioner Stephen H. Burrington last week.

Burrington agreed, said DCR spokeswoman Vanessa Gulati.

"DCR is completely in agreement with the mayor as to the importance of preventing invasive species," she said. Burrington is seeking funding sources for acquatic weed harvesting on the Charles in Waltham.

However, Gulati said only partial funding for the project can come from state funds. She cited state law which limits the state to a 50 percent contribution for such projects, at most.

McCarthy estimated keeping invasive weeds out of the river for 2006 will cost $20,000.

Residents of the Waltham neighborhoods that line a series of coves on the river's south bank said the weeds are not only a nuisance, but can be painful.

Sue Adams, who keeps a canoe tied up on a small dock at the steep bank behind her house, said the weed-harvesting program of the 1990s made a big difference. Before that, the plants were everywhere, and would wrap around paddles and swimmers' legs.

"At one point it was horrible, between the milfoil and the water chestnuts," she said. The chestnuts' leaves are very pretty, but trailing beneath them on a long vine are seed pods bearing sharp, hooked burrs. "You can imagine the pain you'd be in if you stepped on one," Adams said.

The plants thrive near developed waterside areas where garden fertilizers wash off with rainwater into lakes and streams, said David Kaplan, staff scientist at the Charles River Watershed Association.

Once an invasive plant takes over, other plants and animals often cannot live in the water, he said. "The water chestnut is a very invasive plant," he said. It grows so thick, "It can stop light from penetrating into the water."

Without light, water temperatures cool, destroying a habitat of fish and other creatures.

Eurasian milfoil, often just called milfoil, is equally insidious because it can reproduce vegetatively, Kaplan said. Even a small shred of the plant, cast off by a mechanical harvester, can take root and grow to maturity, he said.

Galen Moore is a Daily News Tribune staff writer. He can be reached at 781-398-8004, or gmoore@cnc.com.

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