Spatial and Temporal Variability in DOC-Mediated UV-B Exposure in Rocky Mountain National Park

Brooks, Paul; O'Reilly, Catherine

This research was designed to improve our basic understanding of ecosystem function in a changing environment and to evaluate how these changes may affect species of special concern. Specifically, we 1) identified patterns in spatial and temporal of Dissolved Organic Carbon (DOC) cycling and export in high elevation aquatic ecosystems, and 2) evaluated how variability in climate (both precipitation and UV) can affect aquatic organisms. Three years of research and monitoring in Rocky Mountain National Park have yielded significant insights into how the amount and composition of DOC control UV exposure in aquatic habitats. Consistent with original hypotheses, the primary control on the penetration of UV in surface water is the presence of terrestrially derived fulvic acids in the DOC pool. However, our conceptual model, that had terrestrial DOC peaking shortly after snowmelt due to a hydrologic flush of soils and then declining throughout the summer, turned out to be too simple. Our results indicate that while this spring pulse of DOC is indeed an important temporal control on potential UV exposure, other factors, both biological and physical may be equally important in controlling DOC and UV radiation in aquatic habitats. We have two manuscripts currently in review from this work, with two more planned for the near future.