Show simple item record

dc.contributor.advisorChairperson, Graduate Committee: Mark L. Skidmore and Jean Dixon (co-chair)en
dc.contributor.authorAllen, Jordan Jonen
dc.coverage.spatialBeartooth Mountains (Mont. and Wyo.)en
dc.description.abstractNitrogen is frequently a limiting nutrient in biologic systems. Previous research on alpine streams and lakes in the Beartooth Mountains, Montana/Wyoming has demonstrated nitrate concentrations in waters draining glaciated catchments that are up to ten times greater than comparable adjacent non-glaciated catchments. The enhanced nitrate concentrations in the glacial fed lakes have been associated with increased diatom abundance relative to the snow fed-lakes. However, the source of the enhanced nitrate input remained undetermined, as well as how nitrate concentrations vary temporally during summer melt. This study measured concentrations of nitrate and ammonium and the isotopic composition of nitrate over the 2016 melt-season in a paired catchment system, in the Beartooth Mountains, Montana. The two catchments have similar elevations, atmospheric inputs, bedrock geology, area, and contain lakes, however, one catchment contains a glacier, the other does not. The stream waters in the glaciated catchment showed significantly elevated nitrate concentrations relative to those in the non-glaciated catchment and to catchment atmospheric input, as determined by snowpack nitrate concentrations. Nitrate concentrations in the glacial stream were observed to increase both temporally as the melt-season progressed, and spatially, with distance downstream from the glacier terminus. Ammonium concentrations in the glacial stream were highest close to the glacier terminus, declining with distance downstream, but also increasing during the melt season. Nitrate isotopic values distinguish the stream waters from atmospheric inputs indicating additional nitrate sources in the catchment. Potential additional sources include inorganic nitrogen released from bedrock sources and microbially fixed nitrogen. Abiotic laboratory weathering experiments simulating subglacial conditions reacted deionized water with finely milled bedrock at 4°C, and a modest quantity of ammonium was released. Potassium is often replaced by ammonium in minerals. Rocks from the study area contained ~3% potassium by weight. Ammonium could then be converted to nitrate through microbial processes within the proglacial environment adding to the atmospheric nitrate input to the stream nitrate budget. However, estimated rates of sediment production, and by inference ammonium production, cannot account for the observed nitrate concentrations and flux, indicating an additional nitrate source, which is most likely ultimately derived from microbial nitrogen fixation.en
dc.publisherMontana State University - Bozeman, College of Letters & Scienceen
dc.subject.lcshAlpine regionsen
dc.titleGlacial effects on stream water nitrate: an examination of paired catchments in southern Montanaen
dc.rights.holderCopyright 2019 by Jordan Jon Allenen, Graduate Committee: Eric Boyden Sciences.en

Files in this item


This item appears in the following Collection(s)

Show simple item record

MSU uses DSpace software, copyright © 2002-2017  Duraspace. For library collections that are not accessible, we are committed to providing reasonable accommodations and timely access to users with disabilities. For assistance, please submit an accessibility request for library material.