HR: 0800h
AN: B41D-0753    [Abstracts]
TI: Chemical Character and Biodegradability of Dissolved Organic Carbon in Streams and Rivers of Interior Alaska
AU: * Wickland, K P
EM: kpwick@usgs.gov
AF: U.S. Geological Survey, 3215 Marine St., Boulder, CO 80303, United States
AU: Striegl, R G
EM: rstriegl@usgs.gov
AF: U.S. Geological Survey, 3215 Marine St., Boulder, CO 80303, United States
AU: Aiken, G R
EM: graiken@usgs.gov
AF: U.S. Geological Survey, 3215 Marine St., Boulder, CO 80303, United States
AB: The amount and chemical character of dissolved organic carbon (DOC) in streams and rivers in subarctic Alaska vary according to watershed type and season. In general, DOC concentrations and aromaticity are greatest in streams draining wetland-dominated catchments, while streams that are fed by groundwater or glacial meltwater have lower DOC concentrations and aromaticity. It is not well known, however, whether there are correspondingly wide ranges in the proportions of biodegradable DOC (BDOC), which is important to our understanding of carbon cycling in high latitude systems. We sampled three large rivers and five streams draining various catchment types in the Yukon River basin in Alaska in late winter (under ice), mid-summer, and autumn 2007 for DOC concentration, chemical character, and BDOC. Chemical character of the DOC was determined by fractionation, specific ultraviolet absorbance (SUVA), and fluorescence. BDOC was determined by 3-month incubations, with and without nutrient additions. The concentration and chemical character of DOC varied widely with season, such that DOC concentration, aromaticity (measured as SUVA), and hydrophobic acid content are at a minimum in winter (~ 2-3 mg C L^-1, SUVA < 3.0), peak during spring snowmelt (> 7 mg C L^-1, SUVA > 3.0) and remain relatively high through summer and autumn. BDOC varied from 10% to 30% of total DOC, and was typically greater when nutrients were added. In addition to characterizing the DOC analyses and incubations, we will explore potential links among watershed type, season, and BDOC.
DE: 0414 Biogeochemical cycles, processes, and modeling (0412, 0793, 1615, 4805, 4912)
DE: 0428 Carbon cycling (4806)
DE: 0475 Permafrost, cryosphere, and high-latitude processes (0702, 0716)
DE: 0483 Riparian systems (0744, 1856)
SC: Biogeosciences [B]
MN: 2007 Fall Meeting