HR: 17:05h
AN: B24A-05    [Abstracts]
TI: High-mountain lakes as a hotspot of dissolved organic matter production in a changing climate
AU: * Abood, P H
EM: paul.abood@colorado.edu
AF: Institute of Arctic and Alpine Research, University of Colorado Campus Box 450 , Boulder, CO 80309-0450 United States
AU: * Abood, P H
EM: paul.abood@colorado.edu
AF: Department of Geography, University of Colorado Campus Box 260, Boulder, CO 80309-0260 United States
AU: Williams, M W
EM: markw@snobear.colorado.edu
AF: Institute of Arctic and Alpine Research, University of Colorado Campus Box 450 , Boulder, CO 80309-0450 United States
AU: Williams, M W
EM: markw@snobear.colorado.edu
AF: Department of Geography, University of Colorado Campus Box 260, Boulder, CO 80309-0260 United States
AU: McKnight, D M
EM: diane.mcknight@colorado.edu
AF: Institute of Arctic and Alpine Research, University of Colorado Campus Box 450 , Boulder, CO 80309-0450 United States
AU: McKnight, D M
EM: diane.mcknight@colorado.edu
AF: Department of Civil, Environmental, and Architectural Engineering, University of Colorado Engineering Center ECOT 441, UCB 429, Boulder, CO 80309-0429 United States
AU: Hood, E H
EM: eran.hood@uas.alaska.edu
AF: Department of Environmental Science, University of Alaska - Juneau 11120 Glacier Highway, Juneau, AK 99801 United States
AB: Changes in climate may adversely affect mountain environments before downstream ecosystems are affected. Steep topography, thin soils with limited extent, sparse vegetation, short growing seasons, and climatic extremes (heavy snowfalls, cold temperatures, high winds), all contribute to the sensitivity of high mountain environments to perturbations. Here we evaluate the role of oligatrophic high-elevation lakes as "hot spots" of aquatic production that may respond to changes in temperature, precipitation amount, and pollution deposition faster and more directly than co-located terrestrial ecosystems. Our research was conducted in the Rocky Mountains, USA. Water samples were collected for dissolved organic carbon (DOC), other solutes, and water isotopes over the course of the runoff season along a longitudinal transect of North Boulder Creek in the Colorado Front Range from the continental divide and alpine areas to downstream forested systems. Sources of DOC were evaluated using chemical fractionation with XAD-8 resins and fluorescence spectroscopy. There was net DOC production in the two alpine lakes but not for the forested subalpine lake. Oxygen-18 values showed that water residence times in lakes increased dramatically in late summer compared to snowmelt. Chemical fractionation of DOC showed there was a increase in the non-humic acid content across the summer of 2003 at all elevations, with alpine waters showing greater increases than subalpine waters. The fluorescence properties of DOC and water isotopes suggested that DOC in aquatic systems was primarily derived from terrestrial precursor material during snowmelt. However, fluorescence properties of DOC in high-elevation lakes on the recession limb of the hydrograph suggest DOC derived from algal and microbial biomass in the lakes was a more important source of DOC in late summer and fall. Alpine lakes produced 14 times more DOC on unit area basis compared to the surrounding terrestrial ecosystems. We hypothesize that much of the authochthonous production is a result of algal growth in alpine lakes caused by the increases in nitrogen deposition from wetfall.
DE: 1806 Chemistry of fresh water
DE: 1871 Surface water quality
DE: 1030 Geochemical cycles (0330)
DE: 0400 Biogeosciences
SC: Biogeosciences [B]
MN: 2004 AGU Fall Meeting