HR: 1330h
AN: B33A-04    [Abstracts]
TI: Stable Isotopic Tracking of Autocthonous Carbon in Two Contrasting Ozark Streams
AU: * Ziegler, S
EM: susanz@uark.edu
AF: University of Arkansas Department of Biological Sciences, 632 Science Engineering Building, Fayetteville, AR 72701 United States
AU: Brisco-Townsend, S
EM: sbrisco@uark.edu
AF: University of Arkansas Department of Biological Sciences, 632 Science Engineering Building, Fayetteville, AR 72701 United States
AB: The central role of microbes in biogeochemical processes makes the identification of carbon (C) sources fueling microorganisms critical to our understanding of stream ecosystems. The δ¹³C of biofilm phospholipid fatty acids (δ¹³C_BPLFA) were determined in experiments conducted from July 2002 through July 2003 using ¹³C-labeled bicarbonate to track autochthonous C in two streams. In Moore Creek (MC), an agricultural stream, and Huey Hollow (HH), a forested stream, dissolved organic carbon (DOC) was released in light incubations during all seasons and represented >10% biofilm net primary production. The DOC from light incubations was enriched in ¹³C relative to DOC from dark incubations suggesting algal exudates were a major source of the DOC. The δ¹³C_BPLFA suggest that ¹³C enriched exudates were not utilized by heterotrophic bacterial components in MC. Autotrophic PLFA from light incubations were more enriched in ¹³C while heterotrophic bacterial δ¹³C_BPLFA were similar between light and dark incubations. By contrast, both heterotrophic and autotrophic biomarkers were significantly enriched in ¹³C in light incubations relative to dark incubations conducted in spring and summer in HH. Results suggest the exchange of C between autotrophic and heterotrophic components of biofilm communities differs between nutrient-enriched and depleted streams.
DE: 0400 Biogeosciences
DE: 1615 Biogeochemical processes (4805)
DE: 1806 Chemistry of fresh water
DE: 1845 Limnology
SC: Biogeosciences [B]
MN: 2005 Joint Assembly