Invasive Water Chestnut Threatens Aquatic Growth
Millions of dollars have been spent to remove the invasive water chestnut from the American Northeast. Dating back to the 1880s, the annually rooting aquatic species has clogged many lakes, rivers and waterways—making it difficult for vessel transportation and for fish to survive.
Since 1982, Vermont has continuously tried to manage the hardy growth of these plants. Under the authority of the Lake Champlain Special Designation Act 1990, a 2014 Water Chestnut report targeting future management of the Lake Champlain Basin Program reported: “Long-term water chestnut management trends continue to show positive advances in the reduction of all known water chestnut populations in Lake Champlain – a result of 33 years of effort and approximately 11.5 million dollars.”
Originating from Eurasia, the water chestnut spread by dispersing its seeds downstream through currents and by birds like ducks and geese. The plant floats on the surface of the water to expand its triangular, toothed edged leaves that range between two to four centimeters. Rosettes form at the top of the stem and become anchored in the water. Underneath the surface and at the end of the stems are seeds that have a hard, nut-like appearance. The seeds can grow between two and a half to four centimeters.
The configuration of water chestnuts creates “leaf mats.” The leaf mats—consisting of a large, solid bunch of plants—block out about 95% of sunlight from aquatic vegetation and consume dissolved oxygen, which eventually suffocates aquatic organisms.
Water chestnuts are difficult to remove from any body of water. While there are several ways to do so, the process can become costly and time consuming. Generally, hand-pulling is a technique used to remove water chestnuts from a smaller, less dense area. Mechanical harvesting, chemical treatment, or biological control are also ways to eradicate the spread of the plant in large bodies of water.
The Galerucella birmanica, a leaf beetle, is a predator of the invasive species, feeding on the water chestnuts. Bernd Blossey, associate professor of natural resources at Cornell University, studied these bugs and their impact on diminishing the chestnut population.
“We had to get permission from the Chinese authorities to bring them out and the U.S. authorities to bring them in,” Blossey told the Cornell Chronicle. “We’ve tried 50 different plant species, and the insects are as specific as we’d hoped they were. We’re really, really pleased with the progress we have made.”
One study conducted by researchers at the University of Life Sciences in Lublin and the Cary Institute of Ecosystem Studies investigated the impact on organism communities with depleted oxygen levels caused by the water chestnut in the Hudson River, specifically.
“We found that all locations and microhabitats that we studied supported dense, diverse communities of invertebrates, including insects, oligochaetes, crustaceans and other taxa. The mechanisms by which these animals tolerate short-term hypoxia need to be elucidated,” the researchers wrote. “We suggest that water-chestnut beds in the Hudson are valuable habitats for invertebrate biodiversity and production, and may contribute substantially to fish production.”
The water chestnut is just one of the many invasive species that have gotten a little too comfortable in bodies of water in the Northeast, especially the Hudson River. Even with researchers dedicated to controlling these plants, invasive species require continuous effort to maintain and control.
"I mean, it affects us, even people that are full time guides or captains but even people that are just recreational boaters,” said Phil Bortz, president of the Oswego County River Guides. “I know there's one river in Oswego County that's become completely choked off. You couldn't get a boat with a motor up or down the river because it would just clog your prop."
The invasive species of water chestnuts repopulates quickly, and spreads across bodies of water. Source: U.S. Fish and Wildlife Service, Flickr