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Conservationists worry proposed chemical treatment will harm migratory birds at NC’s Lake Mattamuskeet

A marsh area near Lake Mattamuskeet, which averages two to three feet in depth. (Photo courtesy of Josh Sullivan, WUNC)
A marsh area near Lake Mattamuskeet, which averages two to three feet in depth. (Photo courtesy of Josh Sullivan, WUNC)

As sunset falls over Lake Mattamuskeet in early January, hundreds of waterfowl start flocking together for the night. Despite the overlapping chorus of Canada geese, tundra swans, and various types of ducks, Derb Carter remembers it used to be louder.

This story was reported and written by WUNC

"I've been coming down here for 40 years," said Carter, an avid birder and an attorney with the Southern Environmental Law Center. "[I've] seen this occur over a period of time - the birds disappearing from the lake. It's very concerning."

Several issues plague Lake Mattamuskeet, including a decline in water quality that's led to harmful algal blooms. To address those issues, the U.S. Fish and Wildlife Service is proposing a trial treatment of a chemical called Lake Guard Oxy to reduce the algal blooms, increase water clarity, and increase submerged aquatic vegetation.

While this proposal is just one of several ongoing restoration initiatives, it’s receiving a lot of attention because a label from the Environmental Protection Agency for Lake Guard Oxy indicates that it’s toxic to birds.

'It's the heart of the county'

Lake Mattamuskeet is the largest natural freshwater lake in North Carolina. It lies next to the Pamlico Sound in eastern North Carolina. The 40,000 acre lake makes up the majority of the Mattamuskeet National Wildlife Refuge, which is managed by USFWS.

The lake is nearly centrally located along the Atlantic Flyway, a route migratory birds use to move south for the winter. The refuge is extremely valuable for wintering waterfowl to stop, rest and eat along their journey.

According to USFWS, the refuge attracts more than 200,000 ducks, geese and swans from November through February. About 58,000 people visit the refuge annually to observe the birds, or to hunt and fish in the summer. For rural Hyde County, this brings important economic stimulation.

"The entire community... has a love for Lake Mattamuskeet," said Refuge Manager Kendall Smith. "It's the heart of the county. Everyone has a connection to the lake. Everybody wants to see the health of the lake improve."

Since the early 1990’s, the lake has experienced declining water quality, causing harmful algal blooms, and consequently leading to the complete loss of submerged aquatic vegetation, or SAV, one of the main sources of food for migratory birds.

"There's no SAV because there's no sunlight reaching the bottom of the lake. There's no sunlight reaching the bottom of the lake because there's active algal blooms and suspended sediment in the water column [blocking] the light," explained Smith.

Several compounding factors are causing declining water quality, including run off pollution from nearby farms and invasive common carp, a type of fish.

Nearby private farms surrounding Lake Mattamuskeet are legally allowed to drain their runoff into the lake. Smith says he's working with private landowners who voluntarily want to divert their runoff away from the lake.

Meanwhile, invasive carp uproot SAV and stir up sediment. A $1 million grant from the federal Bipartisan Infrastructure Law is being used to remove one million pounds of carp from the lake over the next 18 months.

Questions and uncertainty over using chemical Lake Guard Oxy

In addition to other ongoing restoration efforts, USFWS is proposing a trial treatment "to reduce the cyanobacteria populations to allow for the reestablishment of beneficial algae... and to increase water clarity in Lake Mattamuskeet," according to the  draft environmental assessment.

Cyanobacteria, also called blue green algae, are the harmful algal blooms blocking sunlight from reaching the bottom of the lake.

The project would be overseen by USFWS, the UNC Institute of Marine Sciences and BlueGreen Water Technologies, the company that created Lake Guard Oxy.

"While treatment of the cyanobacteria with this product is expected to improve water quality, there are potential adverse impacts to wildlife to be considered," the draft assessment states. "The Environmental Protection Agency label for Lake Guard Oxy indicates that it is toxic to birds."

Lake Guard Oxy comes in the form of a pellet that would be applied directly to the surface of the water. The draft assessment says those pellets are "expected to fully dissolve within a matter of hours, limiting the likelihood of consumption by wildlife. There are no research studies available addressing whether birds would consume hydrogen peroxide, the active ingredient in Lake Guard Oxy."

The draft assessment argues "multiple studies show that the cells of birds and bats are remarkably resistant to the oxidative stress" caused by hydrogen peroxide.

However, this information is still alarming to several environmental and conservation groups, including the North Carolina Coastal Federation and the Southern Environmental Law Center.

"We think [this] raises a whole host of concerns given that this refuge was established as a sanctuary for migratory birds," said Ramona McGee, an attorney with SELC.

McGee highlighted the danger of Lake Guard Oxy coming in a pellet form.

"The fact that it dissolves doesn't mean that it lessens the risk," McGee said. "It's still going to be floating there on the surface for waterfowl to be interacting with."

McGee also expressed frustration at what she calls a lack of transparency.

"There's just a lot of uncertainty and a lot of questions that need to be answered before Fish and Wildlife Service proceed with applying a chemical that could very well harm and kill the inhabitants that the refuge was designed to protect," said McGee. "There's a lot of uncertainty around its efficacy. There remain a lot of questions about how different applications turned out."

Lake Guard Oxy has been applied to at least five other bodies of water across the U.S., including Lake Anna in Virginia and Lake Minneola in Florida.

Harry Looney with the  Lake Anna Civic Association said in a phone call his organization had a positive experience while using the chemical in 2022 and 2023. 

"We didn't see any negative or unintended consequences from our applications in either year," said Looney. "Results were pretty much as advertised- no fish kills [and] no observable impacts on other wildlife in and around the area.

"In 2022, there were days when we would go back the next morning, and we'd still see some of it floating on the surface. And that was the desired effect."

In Florida,  Lake Minneola received 14 treatments of Lake Guard Oxy in certain areas between November 2020 and May 2021. The St. Johns River Water Management District oversaw the project. Spokeswoman Ashley Evitt said in an email that during the project time, staff did not observe any adverse ecological effects. Lake Minneola has not received any more algaecide treatments since May 2021.

Still, Alyson Flynn, a coastal advocate with the Federation, worries the proposed treatment is short sighted. Flynn points to the  Lake Mattamuskeet Watershed Restoration Plan finalized in 2018.

"The whole purpose of the watershed restoration plan is to focus on long term solutions" said Flynn. "We want to get to the ultimate reason that the lake is in poor health to begin with, and we don't really feel like a treatment will necessarily pose a solid long-term solution."

Like McGee, Flynn also has outstanding questions, specifically over the EPA label of Lake Guard Oxy.

The label was  updated in March 2023 to remove a single sentence: "Do not apply to shallow water bodies less than three feet deep, or to areas where surface water is stagnant."

Lake Mattamuskeet averages two to three feet in depth.

"Lake Mattamuskeet is a very shallow water body," said Flynn. "Even though that sentence has since been taken out of the [label]... what was the process for removing that? Why was it originally in there to begin with?"

BlueGreen Water Technologies said in an email the original depth limitation was a voluntary inclusion upon the initial commercialization of the product.

"Through ongoing BlueGreen treatments and collection of data via outcomes that have been analyzed, BlueGreen determined that the floating characteristics of the product enables a dependable upper-layer activation without substantial oxidation below the surface of the water," said spokesman Mike Pelz.

Decision expected this spring

USFWS accepted public comment on the proposal last fall. Refuge Manager Kendall Smith is now reviewing those comments.

"Our goal is to take those comments as helpful suggestions so that we can improve this project... and [address] any concerns," said Smith. "We're certainly in touch with any negative impacts to the waterfowl. And if this were to move forward, we would be monitoring very closely ourselves."

Smith said he sees value in the project because it could help reduce algal blooms and bring back submerged aquatic vegetation.

"This idea has caused concern from those are bird lovers and want to help the birds," said Smith. "The ironic part is that's exactly why we're proposing the project: to help the birds and to provide the habitat that they need."

The proposal is subject to state and federal permits. A decision is expected sometime this spring.

"I drive across the lake every morning... and I ask for wisdom and opportunities to see this lake restored," said Smith. "So when opportunities present themselves, I take them pretty seriously before turning them down."