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CAPE FEAR MEMORIAL BRIDGE: Updates, resources, and context

Lake Mattamuskeet chemical treatment moving forward despite worries about its effects on birds

Sunset at Lake Mattamuskeet in January 2024.
Josh Sullivan
The sun sets over Lake Mattamuskeet on a January 2024 afternoon.

The U.S. Fish and Wildlife Service is moving forward with a pilot treatment of a chemical called Lake Guard Oxy to reduce harmful algae blooms, increase water clarity, and increase submerged aquatic vegetation in Lake Mattamuskeet.

"The results of this pilot study treatment and its impact on increasing water clarity would be influential in the efforts to restore (submerged aquatic vegetation) to the lakebed, which would provide essential habitat for fish... and an important food source for waterfowl," the agency said in a press release.

The decision is facing criticism from conservation groups because the Environmental Protection Agency label for Lake Guard Oxy indicates it is toxic to birds.

"The refuge at Lake Mattamuskeet was established to protect birds," said Ramona McGee, an attorney with the Southern Environmental Law Center. "We remain concerned and are disappointed that Fish and Wildlife Service is proceeding with the proposal."

Lake Mattamuskeet is the largest natural freshwater lake in North Carolina. It lies next to the Pamlico Sound in the eastern part of the state. The 40,000-acre lake makes up the majority of the Mattamuskeet National Wildlife Refuge, which is managed by the U.S. Fish and Wildlife Service (USFWS).

The lake is 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.

However, since the early 1990's, water quality in the lake has declined, causing harmful algal blooms and leading to the complete loss of submerged aquatic vegetation, one of the main sources of migratory birds' food.

A shallow area of Lake Mattamuskeet, which averages two to three feet in depth.
Josh Sullivan
A shallow area of Lake Mattamuskeet, which averages two to three feet in depth. Several issues plague the lake, including a decline in water quality that’s led to harmful algal blooms. To address those issues, the U.S. Fish and Wildlife Service plans to use a chemical called Lake Guard Oxy to reduce the algal blooms, increase water clarity, and increase submerged aquatic vegetation.

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

USFWS has been working on restoration efforts and intends to start applying Lake Guard Oxy this month. The agency said the sodium percarbonate-based pesticide will be applied only to four designated areas that make up 400 acres - or 1% - of Lake Mattamuskeet.

The final environmental assessment added several clarifications in response to public comment. It said chemical applications will be limited to "periods of low or no waterfowl abundance to minimize potential impacts on waterfowl."

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

"Results of these monitoring efforts will be reviewed to better understand the beneficial and adverse impacts, the effectiveness of measures to minimize impacts, the effectiveness to control cyanobacteria, and lake and wildlife responses," USFWS said in a statement.

Conservation groups say the treatment is short sighted. They argue focusing on long term restorative solutions would be more effective.

"This is an experimental application of a product at a place that was created to serve as a sanctuary for wildlife," McGee said. "Proceeding with this plan sets a harmful precedent of using our wildlife refuges as a testing ground."

Celeste Gracia covers the environment for WUNC. She has been at the station since September 2019 and started off as morning producer.