HR: 11:50h
AN: B22D-07 INVITED    [Abstracts]
TI: Biogeochemistry of Iron Oxidation in a Circumneutral Freshwater Habitat
AU: * Duckworth, O
EM: owen_duckworth@ncsu.edu
AF: Department of Soil Science, North Carolina State University, Raleigh, NC 27695, United States
AU: Homstrom, S
EM: sara.holmstrom@miun.se
AF: Natural and Environmental Sciences, Mid Sweden University, Sundsvall, SE-851 70, Sweden
AU: Pena, J
EM: jena@nature.berkeley.edu
AF: Department of Civil and Environmental Engineering, University of California-Berkeley, Berkeley, 94720, United States
AU: Zacharias, E
EM: ezachar@berkeley.edu
AF: Department of Integrative Biology, University of California-Berkeley, Berkeley, CA 94720, United States
AU: Sposito, G
EM: gsposito@nature.berkeley.edu
AF: Division of Ecosystem Sciences, University of California-Berkeley, Berkeley, CA 94720, United States
AB: Iron(II) oxidation in natural waters at circumneutral pH, often regarded as an abiotic process, may be biologically- mediated when it occurs in iron-rich redox gradients. West Berry Creek, a small circumneutral tributary flowing through a mixed coniferous forest in Big Basin State Park, California, contains localized iron (hydr)oxide precipitates at points along its course where anoxic groundwater meets oxygenated creek water. These mixing zones establish redox gradients and iron-rich microbial mats that may create microenvironments that promote active biogeochemical cycling of Fe. Water sampling revealed strong correlations between the concentrations of aqueous inorganic species, suggesting a rock-weathering source for most of these solutes. Liquid chromatography-mass spectrometry detected significant concentrations of organic exudates, including low molecular mass organic acids and siderophores, indicating active biogeochemical cycling of iron is occurring in the creek. X-ray diffraction and elemental analysis showed the iron precipitates to be amorphous minerals, such as ferrihydrite. Microbial biofilm communities are associated with the iron (hydr)oxide deposits. Clone libraries developed from 16s rDNA sequences revealed the presence of microorganisms related to the neutrophilic iron- oxidizing bacteria Gallionella and Siderooxidans; in addition, micrographs suggest the widespread presence of sheath-forming bacteria (e.g., Leptothrix). Sequences from these libraries also indicated the presence of significant populations of organisms related to bacteria in the genera Pseudomonas, Sphingomonas, and Nitrospira. These geosymbiotic systems appear to be significant not only for the biogeochemical cycling of iron in the creek, but also for the cycling of organic species, inorganic nutrients, and trace metals.
DE: 0414 Biogeochemical cycles, processes, and modeling (0412, 0793, 1615, 4805, 4912)
DE: 0419 Biomineralization
DE: 0461 Metals
DE: 0463 Microbe/mineral interactions
DE: 0471 Oxidation/reduction reactions (4851)
SC: Biogeosciences [B]
MN: 2007 Fall Meeting