Miller, Matthew听1听;听McKnight, Diane听2听;听Alexa, Katherine听3
1听INSTAAR, Environmental Engineering
2听INSTAAR, Environmental Engineering
3听Cornell University
We studied the impact of a sustained high elevation rain event in mid-summer on the biogeochemistry of dissolved organic material (DOM) in aquatic ecosystems in the Colorado Front Range. In the Green Lakes Valley, the hydrology and the character of the DOM are defined by two distinct periods: snowmelt and baseflow. Surface water samples were collected from the outlet of a small alpine lake as well as the outlet of a larger subalpine lake from the initiation of snowmelt into the fall. From July 7-9, 2006 a continuous low intensity rain event produced approximately 9 cm of precipitation.
As a result of the storm, the fluorescence characteristics of the DOM and the percent fulvic acid contribution to the sample were reset to values similar to those observed during snowmelt at the alpine site but were relatively unaffected at the subalpine site. Similarly, the alpine system was more responsive to changes in primary productivity. These results suggest that alpine ecosystems are more sensitive to hydrologic and biological changes than subalpine ecosystems and that residence times of the lakes as well as watershed area play an important role in regulating stream chemistry.