1a.Objectives (from AD-416):
To assess the impact of Eurasian Watermilfoil introductions into streams in the Western US. Emphasis is to be placed on assessing the changes in insect fauna assocated with the displacement of native vegetation and its implications for the native foodweb. Additional specific consideration is to be given to assessing the introduction and impact of insect biolgoical control agents of Eurasian Watermilfoil in California and Alaska.
1b.Approach (from AD-416):
A combination of field sampling, laboratory assessment and experimental studies will be used to measure and assess the changes found in Western US stream where Eurasian Watermilfoil has invaded. Qualitative and quantitative models will be developed to compare actual sites of invasion with areas through to be high at risk for potential invasion. Cold water springfed streams will be the primary focus of study as they best represent Alaskan waters where Eurasian Watermilfoil is rated to be the State's largest exotic weed threat.
This project addresses objectives 2 and 3 of the parent project which focuses on the integrated management and biological control of several aquatic invasive weeds of the Western United States, respectively. Introduced Eurasian watermilfoil (Myriophyllum spicatum) is such an introduced aquatic weed that has infested many lakes and slow moving waterways in North America and is threatening invasion in portions of the United States as far north as Alaska. USDA-ARS scientists in Albany and Davis California are working with scientists from the University of California Davis on assessing milfoil growth in coldwater spring fed streams in Northern California, including the Fall River. Work is focusing on assessing the impact on Eurasian watermilfoil on native plant species, including changes that occur to additional members of the aquatic food web that supports higher level organism including herbivores, and predators within the stream. Additional studies have been focused on reestablishing native aquatic plants such as horned pond weed (Zannichellia palustris) in the steam bed to more effectively compete with the Eurasian water milfoil. As part of that process, a combination of field monitoring of Z. palustris population dynamics along with laboratory and greenhouse studies on plant growth, seed development and germination have been conducted. Statistical modeling to predict native plant phenology and density in spring fed rivers is continuing.