Spatial and Temporal Variability in the Amount and Source of Dissolved Organic Carbon: Implications for Ultraviolet Exposure in Amphibian Habitats |
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| Authors: | Paul D. Brooks Catherine M. O’Reilly Stephen A. Diamond Don H. Campbell Roland Knapp David Bradford Paul Stephen Corn Blake Hossack Kathy Tonnessen |
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| Affiliation: | (1) Hydrology and Water Resources, University of Arizona, Tucson, Arizona 85721, USA;(2) Department of Biology, Vassar College, Poughkeepsie, New york 12604, USA;(3) Office of Research and Development, US Enviromental Protection Agency National Health and Environmental Effects Research Laboratory, 6201 Cogdon Blvd, Duluth, Minnesota 55804, USA;(4) Water Resources Division, US Geological Survey, MS 415, Lakewood, Colorado 80225, USA;(5) Sierra Nevada Aquatic Research Laboratory, University of California, HCR 79, 198, Crowley Lake, California 93546, USA;(6) Office of Research and Development, US Enviromental Protection Agency, 93478, Las Vegas, Nevada 89193-3478, USA;(7) Northern Rocky Mountain Science Center, US Geological Survey, Aldo Leopold Wilderness Research Institute, 790 E. Beckwith Ave, Missoula, Montana 59807, USA;(8) National Park Service, Rocky Mountains Cooperative Ecosystem Studies Unit, School of Forestry, University of Montana, Missoula, Montana 59812, USA |
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| Abstract: | The amount, chemical composition, and source of dissolved organic carbon (DOC), together with in situ ultraviolet (UV-B) attenuation, were measured at 1–2 week intervals throughout the summers of 1999, 2000, and 2001 at four sites in Rocky Mountain National Park (Colorado). Eight additional sites, four in Sequoia and Kings Canyon National Park/John Muir Wilderness (California) and four in Glacier National Park (Montana), were sampled during the summer of 2000. Attenuation of UV-B was significantly related to DOC concentrations over the three years in Rocky Mountain (R2 = 0.39, F = 25.71, P < 0.0001) and across all parks in 2000 (R2 = 0.44, F = 38.25, P < 0.0001). The relatively low R2 values, however, reflect significant temporal and spatial variability in the specific attenuation per unit DOC. Fluorescence analysis of the fulvic acid DOC fraction (roughly 600–2,000 Daltons) indicated that the source of DOC significantly affected the attenuation of UV-B. Sites in Sequoia–Kings Canyon were characterized by DOC derived primarily from algal sources and showed much deeper UV-B penetration, whereas sites in Glacier and Rocky Mountain contained a mix of algal and terrestrial DOC-dominated sites, with more terrestrially dominated sites characterized by greater UV-B attenuation per unit DOC. In general, site characteristics that promoted the accumulation of terrestrially derived DOC showed greater attenuation of UV-B per unit DOC; however, catchment vegetation and soil characteristics, precipitation, and local hydrology interacted to make it difficult to predict potential exposure from DOC concentrations. |
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| Keywords: | dissolved organic carbon ultraviolet radiation ultraviolet-B amphibians national parks |
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