Abstract: With a floating-leaf growth form and an explosive growth rate, water chestnut (Trapa natans) can grow to completely dominate water surfaces, prompting large changes in ecosystem functionality. The lack of success controlling water chestnut with chemical and physical methods prompted renewed research in biological control, and we are evaluating the potential of Galerucella birmanica, a leaf feeding beetle of Asian origin, as a biological control agent for water chestnut in North America. In addition, we are investigating the ecosystem engineering impacts of water chestnut invasions. Due to the morphology of the plant and the extensive floating beds of vegetation that it can create, dissolved oxygen concentrations can plummet, leading to cascading impacts that affect element cycling and food-webs. In particular, we are researching nitrogen dynamics in water chestnut invaded systems, and exploring mechanisms that explain the loss of inorganic nitrogen when water flows into water chestnut beds.
Approach: We are working to determine the safety of introducing G. birmanica in North America through host-specificity testing and evaluation of the potential ecological interactions with other native insect species. In addition to the traditional sequence of host-specificity testing that scale from petri dishes to indoor enclosures, we will apply demographic approaches to those North American plants found to be in the fundamental host range of water chestnut. This will involve outdoor experiments that manipulate insect attack rates (using a native insect as a proxy) and following the responses of the plants to determine if and how feeding damages translate to impacts on the plant’s life cycle.
In the field, we are monitoring the nitrogen content of water as it flows through water chestnut invaded sites. We are combining this field collected data with laboratory experiments that explore the role of denitrification as a mechanism of nitrogen loss.
Who is involved: Wade Simmons (lead)
Funders: New York Department of Environmental Conservation, NYSIRI, NSF-IGERT Training Program