<i>Potamogeton Crispus</i> Invasion: Impacts on Native Aquatic Plants and Associated Faunal Habitat

Aquatic invasive plants are non-native plants that invade a water body and displace native aquatic plants. Invasion depletes the native plant community's ability to provide ecosystem services, including improved water quality, decreased problematic algae, and increased animal habitat. The loss of these ecosystem services reduces the value of fishing, boating, and swimming opportunities in aquatic ecosystems. The potential changes in plant communities and services are particularly important at sites targeted for restoration because project goals typically include increasing ecosystem services, including wildlife habitat. Curly-leaf pondweed (Potamogeton crispus L.) is a problematic invasive species in North America. To better manage invasion by curly-leaf pondweed, practitioners need to understand its invasion ecology, which includes region-specific growth patterns, mechanisms by which it dominates a system, and the role of native aquatic plants in increasing a system's resilience against invasion. In addition, it is important to understand how invasion by curly-leaf pondweed threatens wildlife habitat for animals like fish. This research project used experimental and observational studies to increase understanding of curly-leaf pondweed ecology which can inform future management. To address questions regarding invasion ecology, we grew curly-leaf pondweed in outdoor tanks and observed them for 16 months. Tanks contained different combinations of native aquatic plants in wetland soil with abundant plant propagules. Additionally, we conducted aquatic plant surveys at the Provo River Delta (Utah, USA) where a curly-leaf pondweed invasion similar to that in the outdoor tanks was underway. In a different study, designed to address questions regarding changes in wildlife habitat, small fish—June sucker (Chasmistes liorus)—were placed in tanks that contained native plants and curly-leaf pondweed. The fish were then exposed to different predator threats and their use of habitats was observed. Together, these studies revealed that (1) growth patterns of curly-leaf pondweed at mid-latitude sites resemble that observed in northern regions of the USA, (2) abundant native aquatic plant propagules can limit curly-leaf pondweed invasion, and (3) curly-leaf pondweed invasion threatens the diverse native aquatic plant community needed by small fish to find adequate refuge habitat.