De Vault Journal of Undergraduate Research X (2007) Links Between Climate Change and the Abundance of Cyclotella stelligera in Alpine Lakes

Alpine lake ecosystems are sensitive to changes in precipitation and temperature, which have significant effects on nutrient loading and the delivery of dissolved organic material (DOM). Previous research has shown that the diatom Cyclotella stelligera experienced rapid fluctuations in abundance in sediment cores, with these fluctuations correlating with a period of drier than average summers. Decreases in precipitation may lower the availability of nutrients to phytoplankton, and increase ultraviolet radiation (UVR) exposure by causing a decline in DOM. Based on patterns in the sediment records, we hypothesized that C. stelligera would thrive under high UVR levels and a low Si:P ratio, which are conditions that would result from decreased precipitation. The study was conducted on Emerald Lake, which is located on the border of Montana and Wyoming in the Beartooth Mountains, to determine the effects of nutrients and UVR on C. stelligera. A factorial experiment was established, in which UVR exposure, phosphorus, and silica were varied, and the effects of these treatments on the abundance of C. stelligera were measured. We found that C. stelligera grew equally well under all conditions tested, indicating that, unlike most other alpine phytoplankton, this species can do well when UVR levels are high. This tolerance to UVR may partially explain the patterns observed in the sediment records