Abstract
Didymosphenia geminata is a microscopic single-celled freshwater diatom. The invasive behavior of D. geminata is greatly altering physical and biological conditions in streams and rivers; the stalk material byproduct that D. geminata produces has the potential to cover up to 100% of stream substrate with a thickness of 20 cm. Even though D. geminata is native to the United States, it is acting like an invasive species. Once only identified in nutrient poor waters, D. geminata has been expanding its native range and is occurring more frequently in nutrient-rich streams and rivers. We conducted a survey of D. geminata in Grand Teton National Park Wyoming and to our knowledge, this is one of the first surveys examining D. geminata in this area. We found and confirmed D. geminata in approximately 7 streams including; Phelps Lake Outlet 1.5x108 cells/m2, Taggert Lake Outlet 2.4x107 cells/m2, Phelps Lake Inlet 2.1 x 106 cells/m2, Jenny Lake Outlet 8.4x105 cells/m2, Flat Creek 2.9x107 cells/m2, Leigh Lake Outlet 1.3x104 cells/m2, and Fish Creek 9.2x105 cells/m2. Potential commonalities in the sites where D. geminata was found and confirmed in Grand Teton National Park include lake outlet streams and high traffic areas.