Wildlife & Nature

Aquatic Invaders Are Taking Over R.I.’s Fresh Waters

Proposed regulations designed to thwart their spread

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.

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.

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  1. It’s about time RI got it’s act together. We’ve been talking about this for decades. Now you say we are the only state that does not have legislation?
    Come on folks!

  2. Wonderful article Todd, it would doubtless be helpful if you or another Eco-writer would provide a list of invasive water plants beside detail pictures. This would enable amateurs, such as myself to identify and record findings as an aid to professional staff. It would also be beneficial if there was a site where findings could be posted.

  3. It is great that DEM is bringing this plight to the forefront and one can only hope that there will be a solution to the problem/s in the near future. One way they could start is to prohibit the flushing of boats at the Bradford boat landing. Boats from all of the coastal communities that have access to the public launches to the salt ponds and ocean flush their motors and wash down their trailers and boats here. This must add invasive species to the local fresh water Pawcatuck River.

  4. Thank you for highlighting this curse of a problem. 2 comments: Years ago Maine’s clear & tough policies regarding aquatic invasives made a difference but I have no idea of the current status there.

    Secondly, many of us in RI treasure our ponds, rivers, etc. and perhaps an organized volunteer effort could make a difference. In other states, volunteers have played a critical role. Heaven knows that DEM could use the support.

  5. Yes good photos beside a list of invasive plant names with contact number….then we can share this list.

    • Denise and James, links in the story do provide lists and some photos of invasive plants to be on the look out for. — Frank Carini, ecoRI News editor

  6. Great article! So very true!!
    We as a state need to work together to solve our freshwater problems.
    Save The Lakes supports the regulations proposed by DEM. Yes, invasive weeds are causing problems for homeowners and lowering their property value, fishermen, recreational opportunities, and hurting the environment. Save The Lakes supports the need to help DEM to improve our freshwater. Statewide lake associations need financial help to develop and maintain lake management programs. RI needs a boat greeter program to help stop the spread of weeds as boat hitchhikers can travel from one lake to another. Recreational boaters and waterfront property owners must be educated and reminded to follow best practices as established in other New England states.
    People created freshwater problems and now, by working together, we can manage them by improving, protecting and preserving our freshwater. But, we need to start immediately!

    Judy Colaluca
    Save The Lakes

  7. So necessary. Let’s keep this growing problem at bay – continuous monitoring and preventing invasives spreading and polluting water quality, and
    moving towards a healthier ecosystem.

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