When aquatic botanist Meghann Bruce found an invasive species known as zombie plant in the St. John River in 2015, she found it in only one place.
She came across the water milfoil while doing botanical research on a river as part of another project.
As part of her research, she examined 171 sites between the Mactaquac Dam and the Princess Margaret Bridge in Fredericton.
In 2018, she returned to the same sites and discovered the invasive plant in more than 60 of them.
Bruce hasn’t checked all those spots since, but she swims in those areas regularly and suspects the water swordtail has spread even further.
“That’s not so surprising because it’s an invasive species, and one of the things they have is a wide environmental tolerance, so they tend to grow really well in new areas that they’re introduced to.”
Aquatic botanist Meghann Bruce has been closely monitoring the spread of the invasive water milfoil, which has earned the nickname zombie plant, since it was first discovered in the St. John River in 2015.
As with many invasive species, Bruce said, now that the water milfoil has become established in the river system, “it’s not possible to eradicate it.”
However, one local group has no intention of giving up without a fight.
The Jemseg Grand Lake Watershed Association launched a pilot project last year to try to contain the plant. The goal is to slow its spread and reduce the number of plants in some hard-hit areas.
As project coordinator Juan Sanchez explained, last fall the team divided the disaster-stricken area into three zones.
In one case, they used scissors to cut the plants at ground level. In another, they pulled the plants out by hand—roots and all. And a third area was left as a control.
In the first two areas, all zombie plants and anything resembling them were removed, including the native water milfoil, to ensure everything was removed.
Sanchez returned to the site this year and counted every plant in all three locations.
Where the intruders were cut down with scissors, he found 30 to 40 plants — about the same number as found last year — but where they had pulled the plants out by the roots, there were only five to 10.
As for the control area, Sanchez said, “Well, there was an incident with the control.”
Last summer, water levels were unusually high, he said. With levels much lower this summer, “the control plot didn’t have the depth to allow the plant to recover.”
European water milfoil has earned the nickname zombie plant because it is impossible to kill. In fact, the only condition it cannot survive is lack of water, so this year’s lower water levels have prevented it from growing as it did last year in the control plot.
John Welsman, a board member of the Jemseg Grand Lake Watershed Association, said the goal of the pilot project was to become familiar with the plant and try to limit its spread.
He added that some property owners tried to get rid of it on their own.
“But what they may not know is that any of those pieces that they may leave behind could become new growth. So … we basically advise people not to try to remove it themselves.”
Sanchez said they may continue the project and set up more test sites in different parts of the lake to see how effective the hand removal method is “in different years.”
“Dense clumps of floating vegetation”
The New Brunswick Invasive Species Council describes the common water milfoil as a species native to Europe, Asia, and North Africa “that was introduced to North America in the 19th century via ballast water or the aquarium trade.”
It has become “widespread” across North America, resulting in “serious impacts to aquatic ecosystems … including the rapid formation and formation of dense mats of floating vegetation that shade native aquatic plants and reduce the amount of oxygen in the water, affecting fish and other species.”
Even a small broken piece can take root and grow a whole new plant, Bruce said. That’s why it’s important to clean boats and other gear when moving from one body of water to another.
This species particularly likes conditions found in lakes and ponds, where the water is often moving more slowly.
“We have a lot of beautiful lakes in New Brunswick that are valued for recreation. And when it comes to those, those are the types of habitats where it could really expand and multiply,” she said.
“In the river, we’re seeing it be a little more selective about where it colonizes. It likes back channels and inland island habitats and bays with slower-moving water.”
But it even grows in the often fast-flowing water near Mactaquac Dam, closer than Bruce might expect.
Wherever it settles, it truly takes root, she added.
“It gets to the point where in some areas, native species are being completely displaced. Or in some places, they’re still growing, they’re just not as abundant.”
Bruce, who teaches at the University of New Brunswick, took students to a creek on the St. John River above Fredericton to teach them plant identification. The creek contained many species of plants, including two that are found in very few places in the province.
“It was great because of the diversity in the area. And it’s a really beautiful place. And now when I go back there, it’s all common milfoil and I can’t find these two rare plants anymore.”
Bruce said the plants pose no real threat to humans, they are “mainly an inconvenience.”
When plants become dense enough, they make recreational activities such as fishing, swimming, and boating difficult.
