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Presented at the NABS Annual meeting, Vancouver, British Columbia, 2004
in PhotoEcology
The influence of UV radiation on the copper binding capacity of humic substances in alpine streams and wetlands in the Colorado Rocky Mountains
M. Appel1, D.M. McKnight1, and M.L. Brooks2. 1INSTAAR, University of Colorado, Boulder, Colorado 80309-0450, 2Department of Fishery and Wildlife Biology, Colorado State University, Fort Collins, Colorado 80523-1474
We investigated the effect of photodegradation by ultraviolet radiation (UVR) on the copper-binding capacity of fulvic acid isolated from streams and wetlands in the Colorado Rocky Mountains. Changes in climate and UVR may alter the quality and quantity of the fulvic acid fraction of dissolved organic matter (DOM) in Rocky Mountain surface waters. Chemical properties of fulvic acid influence benthic communities because fulvic acid attenuates harmful UVR and decreases metal bioavailability. Fulvic acid isolates were collected from streams and wetlands using XAD-8 column chromatography during the spring and summer of 2003. The percentage of fulvic acid was generally greater during spring runoff (45% to 80%) than in late summer (27% to 50%). This trend probably reflects the flushing of allochthonous DOM from soils into the stream during snowmelt. These trends indicate that because of the greater fulvic acid concentrations during spring runoff, the DOM will be more effective in metal binding and light attenuation and offer greater protection to benthic communities than during the summer. The changes in the copper binding affinity of the fulvic acid isolates before and after irradiation with UV light are discussed in terms of implications for metal toxicity to benthic organisms.
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