Aquatic Invaders Are Taking Over R.I.'s Fresh Waters
By TODD McLEISH/ecoRI News contributor
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| In less than seven years this sacred lotus patch has taken over nearly 2 acres of 12-acre Meshanticut Pond in Cranston. (DEM) |
When a Cranston resident planted a sacred lotus in the pond at Meshanticut State Park in memory of a family member in 2014, she didn’t realize the plant was an aggressive invasive species. The lotus, which features enormous floating leaves that shade out native plants, quickly took over a large area of the Rhode Island pond.
Five
years later, 75 volunteers spent 12 hours cutting it back, but they eradicated
just 10 percent of the ever-expanding plant, which today covers 1.83 acres of
the 12-acre pond.
It’s
one of many examples of the challenges the state faces in trying to control and
eliminate aquatic invasive species.
More than 100 lakes and 27 river segments in Rhode Island are plagued with at
least one species of invasive plant, according to the Rhode Island Department
of Environmental Management (DEM). These plants pose threats to healthy
ecosystems, reduce recreational opportunities, and negatively impact the
economy.
“Aquatic invasives are definitely a problem for water quality, but there aren’t a lot of resources dedicated to mapping them and trying to contain them,” said Kate McPherson, riverKeeper for Save The Bay.
“The problem is they can show up in
really pristine areas of the state for a variety of reasons, and a lot of the
plants only need a couple of cells or a leaf to reproduce. They don’t need
seeds. So unless you’re really diligent about scrubbing down your boat and
other equipment after each use, it’s really hard to prevent their spread.”
In
its 2020 fishing regulations, DEM prohibited the transport of invasive plants
on any type of boat, motor, trailer, or fishing gear as a strategy to prevent
the inadvertent movement of aquatic invasive species from one waterbody to
another.
“It’s
essentially an incentive for boaters or anglers to clean off their gear to make
sure they don’t move any plants unintentionally,” said Katie DeGoosh of DEM’s
Office of Water Resources. “It’s part of a national campaign known as Clean Drain Dry to remind anyone recreating
on water how they should decontaminate their gear to avoid spreading
invasives.”
DEM’s
latest effort to combat aquatic invasive species is proposed regulations to ban
their sale, purchase, importation, and distribution in the state. Rhode Island
is the only state in the Northeast that has yet to regulate the sale of these
plants.
The
proposed regulations have the support of Save The Bay, the Rhode Island Natural
History Survey, and the Rhode Island Wild Plant Society.
Those
with aquatic plants in backyard water gardens aren’t the focus of the
regulations because those residents aren’t selling the plants, DeGoosh said.
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| A mat of water chestnut in Olney Pond at Lincoln Woods State Park limits the amount of light available to other aquatic plants, allowing it to quickly displace native species and decrease biodiversity. (DEM) |
The proposed regulations list 48 species of aquatic invasive species whose sale would be prohibited. All but one — sacred lotus — are included on the Federal Noxious Weed List, are banned by other states in the region, were nominated by the Rhode Island Invasive Species Council or are included in the Rhode Island Aquatic Invasive Species Management Plan.
Among
them are Carolina fanwort, a problem species in numerous locations, like Stump
Pond in Smithfield; American lotus, which covers 18 acres of Chapman Pond in Westerly;
Brazilian waterweed, which has invaded Hundred Acre Pond in South Kingstown;
and common water hyacinth, an Amazonian species now found in the Pawcatuck
River in Westerly.
Perhaps
the worst of them is variable milfoil, which has been recorded in 69 lakes and
ponds and 19 river segments in Rhode Island.
“Milfoil
means a million tiny leaves,” said McPherson, who monitors local rivers for
invasive species. “It looks like a submerged raccoon tail, and if you’ve been
paddling in any pond in Rhode Island, you’ve probably seen it. A tiny little
fragment can spread it.”
In
many waterbodies, especially in urban communities, multiple species of aquatic
invasives have colonized.
“They’re
a problem because they can choke out native species and they may not be as good
a food source for animals that eat aquatic plants,” McPherson said. “They’re
also indicative of a water-quality problem. We’re seeing them more commonly in
areas with too much phosphorous or nitrogen in the water. Areas with pollutants
encourage these plants to grow.”
David
Gregg, executive director of the Rhode Island Natural History Survey, also
noted the impact of pollution in helping aquatic invasives take hold.
“People
really care about their lakes, but most lakes in Rhode Island are man-made,
shallow, and polluted by surrounding development — lawns, septics, road runoff
— and so they grow invasive plants like nobody's business,” he said.
Like
at Meshanticut Pond, once the plants become established in a waterbody, they
are difficult to eradicate.
“It’s
a cyclical problem,” McPherson said. “It’s super satisfying to go as a
volunteer to rip it out, and super discouraging to go back a year later and
find that it’s still there. If you don’t get all of the root system, it grows
back.”
Natural
History Survey staff documented the first occurrence of invasive water chestnut
in the state in 2007 at Belleville Pond in North Kingstown. They led numerous
volunteer efforts to manually remove it every year for a decade, and yet the
plant remains. A similar endeavor to battle water chestnut at Chapman Pond in
Westerly barely made a dent in the abundance of the plant.
“It’s
a big problem,” McPherson said. “We need to get folks to think about how their
activities can spread the plants and get them to think about aquatic invasives
as a kind of contaminant.”
The
proposed regulations, if approved, would be enforced via business inspections
by DEM staff. Violators could be fined up to $500 per violation.
Rhode
Island resident and author Todd McLeish runs a wildlife blog.
