[LTER-sbc_all] PhD Seminar - Anna K James - December 4th

[Jenny Dugan]

***Ph.D. Seminar***
 
Anna K James
 Interdepartmental Graduate Program in Marine Science
 
The Effects of pCO2 on Bacterioplankton-Mediated Carbon Cycling 
 
 
Monday, December 4th at 10am
 MSI Auditorium
 
 Committee: Craig Carlson, Debora Iglesias-Rodriguez, Mark Brzezinksi, Uta Passow
 
 Abstract
 Heterotrophic bacteria play a critical role in the marine carbon cycle. They consume 50 % or more of the dissolved organic carbon (DOC) produced in the surface ocean by photosynthesis [1, 2]. Subsequent bacterial respiration results in the conversion of the majority of consumed organic carbon to carbon dioxide (CO2). Collectively, these processes decrease the amount of DOC in the surface ocean and can affect the rate at which recently produced DOC accumulates in the surface ocean. A reduction in DOC accumulation can diminish the contribution of DOC to the vertical export of carbon via the biological pump [3]. Thus, alterations to the marine system that affect bacterial consumption and subsequent respiration of organic carbon can have profound impacts on the marine carbon cycle.
 
 My exit seminar will focus on seawater culture experiments that were designed to assess the direct effects of pCO2 on bacterioplankton consumption of DOC. Results from these experiments provide evidence that short-term exposure to elevated pCO2 enhance the rate of removal of photosynthetically-derived surface DOC by natural bacterioplankton communities. To evaluate potential taxonomic and metabolic mechanisms responsible for these enhanced rates of DOC removal by marine bacterioplankton, I will also present results from a metagenomic analysis. Results from this analysis suggest that elevated pCO2 can alter the taxonomic composition and metabolic potential of natural bacterioplankton communities. Collectively, these studies contribute to a growing understanding of the effects of elevated pCO2 on bacterioplankton-mediated carbon cycling in the surface ocean.
 
 1. Azam, F., Fenchel, T., Field, J.G., Gray, J.S., Meyer-Reil, L.A., and Thingstad, F. (1983). The ecological role of water-column microbes in the sea. Marine Ecology Progress Series 257–263.
 
 2. Ducklow, H.W. (1999). The bacterial component of the oceanic euphotic zone. FEMS Microbiology Ecology 30, 1–10.
 
 3. Passow, U., and Carlson, C. (2012). The biological pump in a high CO<sub>2 world. Marine Ecology Progress Series 470, 249–271.
 
 
 
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Jenny Dugan

Marine Science Institute
University of California
Santa Barbara, CA 93106-6150
Phone: 805-893-2675
email: j_dugan at lifesci.ucsb.edu
http://msi.ucsb.edu/people/research-scientists/jenny-dugan () 
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