HR: 1330h
AN: NB33I-11    [Abstracts]
TI: Stable Isotopic Relationships among Biofilm, Algae, and Dissolved Organic Carbon in two Ozark Streams: Spatial and Temporal Considerations
AU: * Piercey, G L
EM: gpiercey@uark.edu
AF: University of Arkansas Stable Isotope Lab, Fulbright College SCEN601, Fayetteville, AR 72701 United States
AU: Brisco, S L
EM: sbrisco@uark.edu
AF: University of Arkansas, Department of Biological Sciences SCEN601, Fayetteville, AR 72701 United States
AU: Ziegler, S E
EM: susanz@uark.edu
AF: University of Arkansas, Department of Biological Sciences SCEN601, Fayetteville, AR 72701 United States
AB: The identification of carbon (C) sources fueling microorganisms is critical to our understanding of stream biogeochemistry. Biofilm, filamentous algae, and dissolved organic carbon (DOC) samples were collected from two contrasting streams to discern biofilm microbial C sources. Samples were collected from multiple sites, representing a gradient in flow, and over diurnal periods to study the variation in the stable isotopic composition of biofilm in relation to DOC and algae. The stable isotopic composition of biofilm phospholipid fatty acids (δ¹³C_BPLFA) was used to distinguish between heterotrophs and autotrophs. Bulk biofilm and algae were typically enriched (2-6 ‰) in pools relative to fast flowing reaches. The δ¹³C of bulk biofilm and algae also changed diurnally with more enriched values occurring in late afternoon in both streams. Diurnal change in δ¹³CC_DOC, however, was only detected in the nutrient-poor stream. The δ¹³C_BPLFA data from the nutrient-poor stream suggest heterotrophs follow variations in algae and DOC, and were more enriched in ¹³C relative to both algae and DOC. This suggests heterotrophs may utilize exudates from the algae or a specific component of the DOC. The δ¹³C_BPLFA from the nutrient-rich stream were far less dynamic suggesting less preferential use of a specific component of the DOC pool.
DE: 0400 Biogeosciences
DE: 1040 Isotopic composition/chemistry
DE: 1615 Biogeochemical processes (4805)
SC: North American Benthological Society [NB]
MN: 2005 Joint Assembly