In partnership with the New England district of the U.S. Army Corps of Engineers (USACE) and the Connecticut Agricultural Experiment Station, the Lower Connecticut River Council of Governments (RiverCOG) is embarking on a research project to manage the spread of what the USACE describes as the “world’s worst invasive aquatic plant.”

RiverCOG will be part of a water exchange dynamics to better understand and control the alarming spread of the invasive aquatic plant hydrilla that is currently spreading throughout the lower parts of the Connecticut River and its tributaries, according to a press release by the USACE’s regional division. According to the division, “hydrilla has made its home in just about every conceivable freshwater habitat,” including rivers, streams, lakes, ponds, and marshes.

Research conducted in 2019 and 2020 found that hydrilla was prevalent along the Connecticut River, finding its way into ecosystems from the Long Island Sound and the Lower Connecticut River Valley to the town of Agawam, Massachusetts.

“The 2019 and 2020 surveys of hydrilla in Connecticut/Massachusetts waters confirm the plant is spreading and the risk of it spreading further to other regional water bodies is significant,” reports the USACE.

Since then, RiverCOG has been instrumental in initiating the research project since the discovery of the invasive plant in the Lower Connecticut River Valley, according to its senior environmental planner Margot Burns.

Growing populations of hydrilla can pose significant danger to freshwater habitats and its various animal species. Nonthreatening aquatic vegetation is being replaced by hydrilla and is affecting wild rice beds, both of which are major food sources for fish and bird species, respectively, according to Burns. The poisonous effect of hydrilla on fish can, in turn, affect the health of humans as well.

“There is a greater chance of cyanobacteria blooms because there isn’t that water exchange,” said Burns.

Hydrilla can also affect water quality and flow, such as the depletion of oxygen in the water, leading to more disturbances in wildlife.

“It hampers water flow in and out of the creeks because the vegetation is so thick. It prevents the normal exchange of the tidal water in and out of the creeks,” said Burns. “It traps sediment. It [can] potentially can lead to more mosquitoes because there isn’t that water exchange.”

The research study will be conducted in seven identified sites during the summer of 2024, including Chester Boat Basin in Chester. An alternate location in Deep River may be considered as well for research that will be conducted by the USACE and the Engineer Research and Development Center (ERDC).

Ahead of that work, the USACE and ERDC will be applying a tracer dye called Rhodamine WT to its four primary sites, including Chester Boat Basin, in August and September. This dye will help the USACE and its partners understand the water exchange dynamics of those locations, “thus informing the development of individual herbicide treatment plans for control of the hydrilla at each site,” said the press release.

According to the USACE, the bright-red Rhodamine WT dye is a fluorescent xanthene dye that has been used for water tracing since the mid-20th century to quantify time of travel in dynamic waters.” Although the dye will temporarily impact the color of test sites, it is a proven safe, nontoxic substance that will have no significant effects on aquatic organisms. Those using the Connecticut River and the basin for recreation purposes should be at no risk either, said Burns.

The first treatment day, when the dye will be released into Chester Boat Basin, will occur on Tuesday, Aug. 15, and the second one happening on Tuesday, Sept. 12. Days devoted to examining samples will follow as concentrations of the dye-colored water will be collected.

A press conference on the study will be held at the Chester Boat Basin on Wednesday, Aug. 16, at 10 a.m. Those in attendance will include the CT River Conservancy and Rep. Christine Palm. More information on the hydrilla plant and its management in the Connecticut River can be found on RiverCOG’s website www.rivercog.org.