Co-authors: Brooke Dir, Wisconsin Lutheran College; Jenna Brandl, Wisconsin Lutheran College
Title: Fragment growth survival of Myriophyllum spicatum (Eurasian watermilfoil)
Abstract: Eurasian watermilfoil (EWM) fragments can settle in new locations and generate entire plants. Numerous studies have concluded that reproduction by fragmentation aids the aggressive spread of this harmful invasive species. The negative effects of EWM on aquatic environments and local economies motivated us to understand the details of this fragmentation process. A previous field study documented new growth from fragments close to 2 inches in length. However, fragment growth in relationship to initial fragment size has not previously been examined. In addition, limited investigative effort has examined EWM growth in laboratory conditions. We collected EWM plants and cut them into fragments that included at least one node. Fragments were divided into five size groups ranging from 0.5 inch to 2.5 inches to represent the allo-fragmentation process. To investigate fragment survival and growth, we planted fragments in a mesocosm containing sediment collected from a freshwater lake, allowing them to grow for four weeks under simulated summer daylight hours. The fragments that generated new growth were removed from the sediment and measured. While longer fragments were more likely to survive than shorter ones, fragments as short as one inch successfully sprouted. The initial fragment size did not affect the growth length of fragments generating new propagules. Our results reiterate the importance of removing all EWM fragments during manual and mechanical treatment to limit the spread of EWM. The possibility of new EWM growth from small fragments should be kept in mind as resource managers select and implement management strategies.
Bio: Isabella Scheibl is a senior majoring in environmental studies at Wisconsin Lutheran College in Milwaukee. Her areas of interest include invasive species, wetlands, and fire ecology. Isabella served as a land management intern at Woodland Dunes Nature Center, where she researched invasive species management effects. After graduation, she will attend graduate school for conservation.