HR: 16:15h
AN: B24D-02    [Abstracts]
TI: Carbon and Manganese Cycling in the Columbia River's Estuarine Turbidity Maxima in the South Channel
AU: * Bräuer, S L
EM: Brauers@ebs.ogi.edu
AF: OHSU School of Science and Engineering, 20000 NW Walker Rd., Beaverton, OR 97006, United States
AU: Kranzler, K
EM: kkranzler@stccmop.org
AF: OHSU School of Science and Engineering, 20000 NW Walker Rd., Beaverton, OR 97006, United States
AU: Tebo, B M
EM: tebo@ebs.ogi.edu
AF: OHSU School of Science and Engineering, 20000 NW Walker Rd., Beaverton, OR 97006, United States
AB: The Columbia River represents the largest input (60-90%) of fresh water to the California Current System, and provides a major source of dissolved manganese and nutrients to the coastal waters. Researchers have identified upper Estuarine Turbidity Maxima (ETM(s)) as hot spots for microbial activity, and it is here that extensive manganese cycling is thought to occur. Most probable number counts of microorganisms within the ETM have revealed that the cultivable numbers of manganese-oxidizing bacteria are not statistically significantly different than that of other heterotrophs when grown on defined media with simple carbon sources or low concentrations (0.05%) of casamino acids and were in the range of 10³ - 10⁴ cells per mL. Similar numbers of heterotrophs (9.3 X 10³ cells/mL) were found using a nutrient-rich complex medium; however, the numbers of manganese-oxidizers were significantly lower (~13 cells/mL). Approximately 100 different manganese-oxidizing bacteria were isolated from different media and are being phylogenetically characterized. Measurements of dissolved, ascorbate-reducible and total Mn by inductively coupled plasma- optical emission spectroscopy revealed that concentrations of Mn are positively correlated with turbidity and thus are higher during an ETM event. In addition, dissolved, total, and ascorbate-reducible Mn were all negatively correlated with salinity, supporting the idea that the manganese originates in the river and is diluted by the seawater originating off the coast. Uptake of ¹⁴C-labeled bicarbonate in response to various electron donors (nitrite, ammonium, thiosulfate, or Mn(II)) was stimulated during an ETM event but not before or after, indicating that these electron donors may serve as potential energy sources for carbon fixation. Taken together, our results further demonstrate that ETMs are zones with high microbial activity and that the ETM microbial communities harbor the potential for carbon fixation even in the relatively nutrient-rich environment of the upper Columbia River estuary.
DE: 0410 Biodiversity
DE: 0439 Ecosystems, structure and dynamics (4815)
DE: 0448 Geomicrobiology
DE: 0458 Limnology (1845, 4239, 4942)
SC: Biogeosciences [B]
MN: 2007 Fall Meeting