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Spatial and temporal patterns in bacterioplankton community composition in the Santa
Barbara Channel

I am using a four-year time-series, collected on the Plumes and Blooms cruise program, to
compare the relative magnitudes of temporal and spatial variability in bacterioplankton
community composition (BCC) in the heterogeneous, upwelling-driven coastal Santa Barbara
Channel. I am also testing the hypothesis that we can better explain bottom-up effects on BCC
by incorporating remotely-sensed as well as in situ parameters, such as phytoplankton
characteristics and dissolved organic matter (DOM). This work was begun under NSF funding and
a NASA Earth and Space Science Fellowship; DNA sequencing is funded by the Santa Barbara
Channel Marine Biodiversity Observation Network.


Bacterioplankton growth on DOM from nutrient-stressed diatoms

Nutrient stress can impact phytoplankton production of DOM - does that lead to subsequent
effects on bacterioplankton growth? I investigated this in a joint project with Laura Windecker,
co-supervised by Craig Carlson and Mark Brzezinski. Our evidence says yes, although it's complicated.

In a field study in the Santa Barbara Channel, we found that dissolved organic carbon (DOC)
remineralization and bacterial growth efficiencies both increased as a mixed diatom bloom
became increasingly silicon-stressed and fresh DOC accumulated in the system (Wear et al., L&O 2015;
Nelson and Wear, 2014). A series of lab experiments, where DOM from nutrient-stressed diatom
cultures was fed to bacterial communities, suggested that both the stressing nutrient (nitrogen,
silicon, or both) and diatom source species affected short-term DOC consumption and bacterial
growth efficiencies, while long-term effects were mainly related to diatom source species identity
(Wear et al., Marine Chemistry 2015).


CDOM photobleaching and bacterioplankton in the Santa Barbara Channel

I am expanding on my time-series work by more directly studying one potential driver of a
relationship between BCC and DOM utilization - that is, the effects of photobleaching of
chromophoric DOM on rates of DOM processing by bacterioplankton and bacterial community
composition, and the subsequent effects on the fate of DOM in the Santa Barbara Channel. Field
samples are experimentally bleached and remineralized, with environmental context derived
from satellite remote sensing data. This project is funded by a NASA Earth and Space Science
Fellowship.


DOM and bacterioplankton community ecology in a blackwater estuary

My master's thesis research focused on the bottom-up effects of DOM composition on
bacterial community composition (BCC) and metabolic capability using Biolog plates (BMC) in
Winyah Bay, South Carolina, and its four blackwater tributary rivers. Across a seasonal DOM
gradient, we found that BCC was more strongly related to DOM composition, particularly those
properties indicating a phytoplankton or cypress swamp origin of the DOM; BMC was associated
with DOM bioavailability and physicochemical factors such as inorganic nutrient concentrations
(Wear et al., 2014).



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