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Medford residents can check out the mechanical harvester currently making its way down the Mystic, ‘eating’ invasive plants as it goes.
By Natalie Milleremail@example.com Medford Transcript Posted Aug 25, 2010 @ 04:00 PM Last update Aug 25, 2010 @ 04:16 PM Medford —
What’s 35 feet long, 15 feet wide, bright orange and has been “eating” water chestnuts from the Mystic River?
If you’ve been strolling by the waterway, you may recognize the description as the enormous mechanical harvesting device being used by Groundwork Somerville in conjunction with the Mystic River Watershed Association in an effort to remove the invasive water chestnut plants that have begun clogging the Mystic over the past couple of years.
“A single one of these plants can grow up to 15 feet long,” said Brad Arndt, Mystic River project coordinator from Groundwork Somerville, one of 18 affiliates of Groundwork USA, a nonprofit environmental organization that promotes sustainable community development and green revitalization in cities across the United States. “They have been exploding all over the area creating a dense mass of vegetation. It is affecting water quality and impeding navigation all along the river.”
Native to Asia, Europe and Africa, the Trapa natans, or water chestnut, is an invasive species of plant that was purportedly introduced to the area by a Cambridge horticulturalist in 1897 as an ornamental plant for Fresh Pond.
The flat, floating leaves create a mass over the water surface of any slow moving waters and crowd out native plants that serve as food and shelter for indigenous aquatic species. The expanse of plants can also lead to lower dissolved oxygen levels in the water, which can lead to quantities of fish kills in the affected area.
Currently, the spread has affected the Mystic River as well as the Arlington Reservoir.
The Mystic River Watershed Association, the Friends of the Mystic River, the Riverside Yacht Club and the Massachusetts Water Resources Authority as well as dozens of their volunteers have been working against the water chestnut problem for several years. Hand pulling, once able to handle the spread of the species, has reached the limit of its capabilities.
“The yacht club generously donated money to the effort to get the volunteer efforts underway this year,” said Arndt. “But the growth is dense.”
Partnering with the community outreach programs of Groundwork Somerville, the groups have recently accessed a three-year grant from the Massachusetts Environmental Trust, a source of funding for the protection of water resources in the state. Since 1988, the MET has dispersed over $17 million in these types of grants.
The three year grant will allow the operation of two very large machines — a “hydro-rake” which pulls the vegetation away from the shoreline to then allow the mechanical harvester to pull the plants out of the water. The harvesting prevents the water chestnuts from further seeding into the favorably sedimentary riverbank so conducive to the invasive species growth.
“We know that complete eradication isn’t possible in just a few short years, but what we’re really hoping that by running the harvester for the next couple of years, we will significantly deplete the seed bank,” Arndt said. “Meanwhile, we can come up with a systemic process that will keep working to have fewer and fewer plants and eventual we can eradicate the species from the area.”
Efforts such as those of the MRWA have proven effective eradicators of the species in many areas such as the Blair and Yates Pond in Cambridge, the Little Pond in Belmont, Alewife Brook and Spy Pond in Arlington.
Arndt realizes it is essential to continue the effort and continue the volunteer support, but he is pretty confident about it because of the encouragement the harvesting has met from the Mystic River communities.
“People have been very curious, when they see the huge dumpsters full of plants, and the two monolithic machines grinding in the river, but when we have explained that we are pulling out the water chestnuts, people seem very relieved,” said Arndt. “There’s sort of this ‘it’s about time’ thing people are expressing to us.”
To ease the public’s questions about the effect that the process will have on the river and the surrounding banks, Arndt assures that in order to receive the grant money as well as permission from the surrounding cities, there are a strict order of conditions surrounding the operation of the mechanical harvester and the hydro-rake.
“We had to apply to the conservation commissions and the approval process took several months,” he said.
As part of the conditions of the project, there would need to maintain minimal soil disruption, and as Arndt reports, “So far, so good. But we are definitely held to do any repairs to the area from the project — that was part of the deal.”
The removal process should take three to four days to collect approximately an acre of water chestnuts.
“We can operate in inclement weather, but nothing too crazy,” said Arndt.
So barring any climatic extremes, the giant orange harvesting beasts should be grinding by the Mystic River, clearing the ways for better boating and fishing with plenty of time for Labor Day weekend.
— For more information about the MRWA efforts to eradicate invasive species, visit mysticriver.org.