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</p><p><font size="+1"><b>***Ph.D. Seminar***</b></font></p>
<p><b>Anna K James</b><br />
Interdepartmental Graduate Program in Marine Science</p>
<p><i><b>The Effects of pCO2 on Bacterioplankton-Mediated Carbon
Cycling </b></i><br />
</p>
<p><b>Monday, December 4th at 10am</b><br />
MSI Auditorium<br />
<br />
<b>Committee: Craig Carlson, Debora Iglesias-Rodriguez, Mark
Brzezinksi, Uta Passow</b><br />
<br />
<b>Abstract</b><br />
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.<br />
<br />
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.<br />
<br />
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.<br />
<br />
2. Ducklow, H.W. (1999). The bacterial component of the oceanic
euphotic zone. FEMS Microbiology Ecology 30, 1–10.<br />
<br />
3. Passow, U., and Carlson, C. (2012). The biological pump in a
high CO<sub>2 world. Marine Ecology Progress Series 470,
249–271.<br />
<br />
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</p></span></div><br /><br />--<br signature="separator" /><div align="" left""=""><font face="Tahoma" size="2"><b>Jenny Dugan</b><br /></font></div><font face="Tahoma" size="2">Marine Science Institute<br />University of California<br />Santa Barbara, CA 93106-6150<br />Phone: 805-893-2675</font><font face="Tahoma" size="2"><font #191970""="" color=""><font color="#000000"><br />email: j_dugan@lifesci.ucsb.edu<br /></font></font></font><font face="Tahoma" size="2"><a href="" http:="" index.html""="" sbc.lternet.edu="">http://msi.ucsb.edu/people/research-scientists/jenny-dugan </a></font><font 2""="" face="Tahoma" size=""><font #191970""="" color=""><font size="2"> </font><br /></font></font><font color="#2f4f4f" face="Tahoma" size="2"><a href="" http:="" index.html""="" sbc.lternet.edu=""><font color="#000000">SBC LTER:</font> </a></font><font face="Tahoma" size="2"><a href="" http:="" index.html""="" sbc.lternet.edu=""> http://sbc.lternet.edu/index.html</a></font><font face="Tahoma" size="2"> </font><br /><div><span style="line-height:9px;font-family:arial,sans-serif"><font size="2">Explore Beaches!</font> <a href="http://explorebeaches.msi.ucsb.edu/" target="_blank"><font size="1">http://explorebeaches.msi.ucsb.edu/</font></a></span></div></span>