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Nashua urged to continue fight against invasive species

Union Leader Correspondent

April 15. 2013 10:52PM

NASHUA - For the third year in a row, harvesting is expected to take place along portions of the Nashua River to prevent the spread of water chestnut and other invasive aquatic weeds.

On Wednesday, the aldermanic Finance Committee will be asked to authorize the spending of nearly $30,000 to help clean up the weeds, which are especially troublesome in the Mill Pond and canal section of the river inside of Mine Falls Park.

Work began in 2011 to harvest water chestnut, or Trapa natans, from Mill Pond, a project that is expected to take about five years to complete.

"Once introduced to an area, water chestnut rapidly displaces other plants and forms dense, monotypic stands that eliminate open water. Adverse impacts associated with water chestnut infestations include water quality deterioration, loss of fish and wildlife habitat, accelerated eutrophication and severe access impairments for recreational activities," says a letter from Aquatic Control Technology Inc. to Nick Caggiano, superintendent of Nashua's Parks and Recreation Department.

According to the document, Aquatic Control Technology was hired in the summer of 2011 to initiate a large-scale water chestnut harvesting program in Nashua. At the time, about 14 acres of dense water chestnut growth was documented in the Nashua River, covering portions of the water and beginning to cause ecological hardship to native plants and animals.

During the first summer, an estimated 507 tons of water chestnut was removed from the river, according to the letter from biologists Peter Beisler and Marc Bellaud.

"Continuing water chestnut harvesting efforts in the Nashua River is strongly recommended for the 2013 season," said the biologists. "We do expect to see some reduction in plant density in 2013."

Aquatic Control Technology is recommending two harvests of the invasive aquatic weeds this year - one in late June and one in late July or mid August - just west of Mine Falls hydroelectric dam.

As part of the project, the harvested weeds are brought to the landfill and composted.

"The harvesting will need to be done for four to six consecutive years before there will be a noticeable drop in population," says a memo written to Mayor Donnalee Lozeau. "This is due to the fact that the water chestnut seeds can remain active for up to 10 years on the river bottom."

According to the biologists, efforts to remove the invasive weeds in the Nashua River are complicated because of a significant water chestnut infestation that is present upstream in Massachusetts.

Wednesday's meeting begins at 6:30 p.m. at Nashua City Hall.

Environment Politics Nashua