Introduced into the United States by aquatic gardeners in the late 1800s, the water chestnut flourishes in shallow, slow-moving bodies of water, such as lakes. A one-acre patch can increase to a hundred acres in a year, crowding out vegetation that fish and other aquatic life rely on for food. The leaves absorb sunlight, causing the water to heat up.
Worse, when the annual plants die and sink to the bottom each fall, their decomposition depletes the water of vital dissolved oxygen.
Water chestnuts don't just cause environmental damage; they also interfere with human recreation. Fishing, boating, and swimming can become almost impossible, and the plant's seeds, sharp enough to pierce shoes, pose an additional hazard.
As far as anyone knows, nothing eats these plants, said Kelly Germann, the conservancy's conservation coordinator. It's up to humans to keep them in check.
Despite removal efforts - some with six-digit price tags - the species is now established throughout the Middle Atlantic and New England regions. But so far, it's made only tentative inroads in New Jersey and Pennsylvania.
The volunteers are trying to prevent Lake Delmont's water chestnut population - one of the state's largest - from taking hold and spreading down Unami Creek, which flows into and out of the manmade lake.
In mid-August, every remaining plant will drop up to 20 mature seeds - each of which can produce 15 cabbage-size rosettes - into the mud below. Scientists think they can remain viable for a decade. A few plants have been spotted downstream.
