Graduate Degree Type
Annis Water Resources Institute
Dr. Sarah E. Hamsher
The growth of starry stonewort (Nitellopsis obtusa), an aquatic invasive species, in two Michigan Lakes, and its suitable habitats in the Midwest and Northeast United States Aquatic invasive species are a major threat to freshwater ecosystems, but gaps remain in our knowledge on how these species invade, grow, and thrive. This thesis aims to understand how an invasive macroalga, Nitellopsis obtusa (starry stonewort), grows within the littoral zone of two drowned river mouth lakes and suitable habitat preferences across 17 Midwest and northeast U.S.A. states to aid in aquatic invasive species management. In chapter II of this thesis, I documented the growth of N. obtusa in two Michigan lakes to determine differences in its growth between a residential reference site (P-RES-Ref), a site previously managed for Myriophyllum spicatum and N. obtusa (P-RES-Mgmt), a private marina (P-MAR), and a previously restored large bay on Muskegon Lake (MUSK). Snorkel surveys were conducted biweekly to destructively harvest quadrats (N = 6) at each site for Nitellopsis obtusa and other associated plants from July-October 2020 and wet and dry weight subsequently recorded. The total and relative abundance of N. obtusa increased significantly over the growing season (p < 0.05) and differed between some sites (p < 0.05). The P-MAR and P-RES-Ref sites both had a high biomass of N. obtusa, but only the P-MAR site also had a high relative abundance of N. obtusa per quadrat, suggesting N. obtusa growth differs significantly between sites, even within the same waterbody. Marina sites should be managed and monitored, whereas sites with higher diversity (e.g., P-RES-Ref) should be managed carefully so as not to lead to additional losses of the native flora. In chapter III of this thesis, I analyzed the potential habitat suitability using presence-only herbarium records across a regional scale in the invaded range of Nitellopsis obtusa using random forest and boosted regression modeling techniques. Models were built using land cover, bicarbonate concentrations, and climate variables for the Midwest and northeast United States 6 from the lake multi-scaled geospatial and temporal database (LAGOS) and WordClim. Results indicated N. obtusa prefers highly developed habitats and connectedness between inland lakes by roads with a potential expansion in some states, specifically in the northeast. These models can contribute to early detection plans for lakes and states that do not have documented populations of N. obtusa currently to assist in halting the spread of this aquatic invasive species.
Neuman, Emily, "The growth of starry stonewort (Nitellopsis obtusa), an aquatic invasive species, in two Michigan Lakes, and its suitable habitats in the Midwest and Northeast United States" (2021). Masters Theses. 1026.