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North Carolina Coastal Collaborations Focus on Invasive Hydrilla

North Carolina Sea Grant works collaboratively against an invasive aquatic plant

By Katie Mosher and Nichole Riddle, North Carolina Sea Grant

Hydrilla verticillata may have been in North Carolina for decades, but experts and volunteers alike are drawing attention to its spread. 

“This invasive aquatic plant has moved from freshwater lakes to coastal plain creeks, and now into the Chowan River and Albemarle Sound — waters that are nurseries for many important commercial and recreational fisheries,” notes Gloria Putnam, North Carolina Sea Grant coastal resources and communities specialist. 

Putnam leads a Hydrilla sampling effort that includes the Chowan Edenton Environment Group and the Chowan Soil and Water Conservation District. Community volunteers gather data using tablet computers and software that she adapted for the project. 


Hydrilla reproduces readily through fragments and produces tubers that can lay dormant for up to seven years. It is considered an invasive, noxious weed at state and federal levels — it causes economic, ecological or other harm. 

Hydrilla can grow in water as deep as 20 feet and, in lab experiments, in salinity as high as 18 parts per thousand, levels of much of the state’s estuarine waters. 

In waterways, the plant can hinder boat access and develop a monoculture, limiting overall biodiversity. Hydrilla also can be a carrier for a neurological bird disease. 

“The use of citizen scientists in this project has proven valuable to the community,” says Jack Thigpen, North Carolina Sea Grant’s extension director. “Giving local residents the opportunity to collect this data themselves, and in a scientifically responsible manner, has opened the door for more conversation and action in the region.”

Hydrilla was found at 77 of 366 sampling points in the Chowan River and Albemarle Sound. “Chowan County and other communities can use the survey data to help make management decisions regarding treatment,” says Putnam, who also serves on the Mid-Atlantic Panel on Aquatic Invasive Species. 

Well-planned and comprehensive treatment will be important for successful control. Getting the right herbicide concentration is difficult in areas where water flows quickly, and downstream treatment won’t be as effective if there’s an infestation upriver. 

The collaboration to address Hydrilla in northeastern North Carolina has earned multiple honors. A multimedia campaign earned a national APEX Communications Award of Excellence. North Carolina Sea Grant produced videos with the Albemarle-Pamlico National Estuary Partnership, and colleagues from Chowan County and NC State University’s Department of Crop Science.

The videos are ideal for classrooms and community programs. “Awareness is key to successfully managing this invasive plant,” Putnam adds. 

The N.C. Invasive Plant Council also presented Putnam with an Excellence in Action Award for her ability to leverage various resources. “The outcome was the first real insight to the extent of the Hydrilla infestation in the area,” notes Rob Emens, with the N.C. Division of Water Resources’ Aquatic Weed Control Program.

Some of the youngest partners also have been recognized. Students at John A. Holmes High School won $3,000 in state and national grants to increase Hydrilla awareness, design a rake to clean off boat axles and to provide special composting barrels.

Their message: Prevention is better, and easier, than treatment. “Don’t let it spread anymore,” says junior Kady Willis.

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