PARENT SESSION
OOS 2: Anthropogenic Disturbances to Western Alpine Lakes: Past, Present, and Future .
Organized by: JE Saros and CE Williamson
Monday, August 2, 8:00 AM to 11:30 AM, Meeting Room E 143.
Shifts in alpine phytoplankton community structure in the Rocky Mountains due to anthropogenic nitrogen deposition.
Saros, Jasmine*,1, Interlandi, Sebastian2, Michel, Timothy1, Wolfe, Alexander3, 1 University of Wisconsin-La Crosse, La Crosse, WI, USA2 Drexel University, Philadelphia, PA, USA3 University of Alberta, Edmonton, Alberta, Canada
ABSTRACT- A common shift in diatom assemblages has occurred in alpine lakes of the western U.S., with Asterionella formosa Hassall and Fragilaria crotonensis Kitton replacing typical alpine diatom taxa since the 1950s. Enhanced atmospheric nitrogen (N) deposition is often invoked as the causal factor driving these shifts. However, while both of these taxa are frequently reported in mesotrophic temperate lakes, information on their N requirements is relatively sparse. We explored the distribution patterns and resource requirements of these taxa in alpine lakes of the Beartooth Mountains, situated in the central Rocky Mountains. Nutrient enrichment experiments were conducted along with batch culture experiments in which the N, phosphorus (P), and silica (Si) growth kinetic parameters were measured. In addition, the distribution of diatom taxa in a suite of Beartooth lakes was explored in relation to a variety of physicochemical parameters, which included dissolved and particulate nutrient concentrations as well as seston nutrient ratios. Sediment cores from these lakes were also examined to assess temporal changes in the diatom communities as well as associated sedimentary chemistry. Our results suggest that Asterionella and Fragilaria are excellent phosphorus competitors that become abundant under higher nitrogen loading. In conjunction with N isotope data from the sediment cores, our results indicate that enhanced atmospheric N deposition is driving these changes in diatom community structure.
Key words: nitrogen, alpine