Documenting Macrophytes and Their Habitat Preferences in Southeastern South Dakota
One of the biggest environmental problems that waterbodies currently face is eutrophication. When eutrophication occurs in lakes, phytoplankton dominance increases and macrophyte populations decrease. Macrophytes are aquatic plants, and when their populations change, they can be used to detect eutrophication and indicate lake health. Despite this novel use of macrophytes, the state of South Dakota has few, if any, baseline public records of its macrophyte species. In an effort to establish a record and work towards the use of macrophytes as potential eutrophication indicators in South Dakota, this study seeks to provide a better understanding of the macrophytes that occur in the southeastern portion of the state and the relationships they have with lake habitats. The objectives of this study were to 1) survey the macrophytes of southeastern South Dakota, 2) evaluate the relationships between existing macrophytes and the physical and chemical characteristics of their lakes, and 3) determine if there are any predictable habitat preferences. The survey was conducted at a total of 78 sample sites among two lakes during mid-summer 2020. Macrophyte samples were taken using a weighted sampling rake, substrates were visually estimated, and dissolved oxygen was measured. Overall, ten different macrophytes types, including emergent, submerged, and free-floating species and genera, were recorded among sample sites. West 81 Lake had the highest species richness, with nine species present and a significantly higher (p< 0.05) average species richness than Island Lake. Additionally, West 81 Lake showed a significantly higher (p<0.05) presence frequency of silt/muck substrates than Island Lake and a significant positive (p< 0.05) relationship between percent silt/muck and species richness. Both lakes demonstrated a significant negative (p< 0.05) relationship between percent clay and species richness. As the results suggest, both percent silt/muck and percent clay may play important roles in determining the types of macrophytes in southeastern South Dakota lakes, and silt/muck dominated habitat systems appear to be the preference for a diverse array of macrophytes.