, Newburyport, MA

July 9, 2009

Race is on to eradicate invasive water chestnut weed

By Lynne Hendricks

AMESBURY — Even as residents along Lake Gardner grapple with how to control a lake bottom teeming with milfoil, an invasive species threatening to deplete the lake of oxygen and force native species into extinction, another invasive species with even greater ability to overtake the ecosystem has quietly emerged to threaten nearby Lake Attitash.

Members of the Lake Attitash Association were granted an emergency order from the Conservation Commission this week that will allow volunteers to fan out along Attitash's back river region this weekend to pluck a thriving crop of water chestnut while the weed is at a manageable stage of development.

"We are poised to begin an emergency eradication program," said conservation agent John Lopez. "Evidently these plants are just about ready to seed. I issued them an emergency certification to allow them to go in and pull these plants."

Lopez said the group is waiting for the weather to clear before heading out on the lake, and volunteers are needed.

"They have 30 days (per the order)," Lopez said. "They hope to do it as soon as the weather clears. They need to pull these things out this weekend."

If the flowering, floating plants are allowed to drop their seeds, as they typically do between mid-July and the beginning of August, the species could prove catastrophic for the lake environment.

"Water chestnut is highly invasive, and if left alone could take over our lake in a few short years," said LAA representative Katie Karatzas in her petition to the commission. "One acre of water chestnut can produce enough seeds to cover 100 acres the following year,"

The water chestnut, or Trapa natans, is a floating, leaved vine that forms a canopy over the surface of lakes and ponds where it takes root. It can become so dense in such a short period of time that it quickly impedes navigation on the body of water and restricts swimming and recreational fishing.

Instead of being a positive for local fish populations, however, the decomposing plant settles on the bottom of the water and snuffs out native plants that fish populations depend on. Over time, the weed reduces dissolved oxygen levels in the shallow portions of the lake, which further threatens fish populations.

The University of Maine Cooperative Extension reports an outbreak of the weed in Lake Champlain cost $3.7 million to eradicate over a period of 18 years.

"That's why people have to clean off their kayaks and their boats when they go from one water body to another, because it's a real nuisance," Lopez said. "It's rather aggressive."

The weed was found in the back-river section of the lake when the state Department of Conservation and Recreation hosted a weed identification class at the site on July 1. DCR Lakes and Ponds coordinator Jim Straub identified the species and helped Attitash volunteers understand the need for taking immediate action.

"The problem is at a manageable size right now," Karatzas said. "Water chestnut is an annual species, which reproduces only by seed ... . Persistent removal of the plant prior to seed drop can dramatically reduce the population over time. Each year will be less work until the weed is gone. Then we can take a proactive approach and simply monitor the lake a couple times each year."

Those with kayaks and canoes who are interested in helping the effort are urged to contact the Lake Attitash Association by e-mailing

"Our goal is to solicit volunteers to hand pull the weed as seen in the guide to hand pulling water chestnut," wrote Karatzas. "The volunteers will work from kayaks and canoes, dumping to a pontoon boat. The removed weeds will then be transported to a truck and brought to a local composting site."

For more information on water chestnut, visit Http://