Abstract

1
The Effects of Trophic Complexity on the
Production, Abundance and Community Structure of
Bacterioplankton
Abstract
Aubrey Cano1, Elisa Wallner, Craig Carlson
T-RFLP pattern after HAE III digest
DOMINOs (Dissolved Organic Matter IN the Ocean)
is a multi-institutional project that asks the
question How does varying the release
mechanisms of DOM affect the quality and quantity
of DOM? The three main release mechanisms include
1) direct release (via phytoplankton exudation)
2) zooplankton release via sloppy feeding and
release and 3) viral lysis or prokaryotic and
eukarytic cells. In the first field season, we
examined the bacterial response to these
differing DOM production mechanisms by monitoring
changes in bacterial production and community
structure shifts. We participated on a
Chesapeake Bay cruise in July 2004 looking at DOM
produced in the light during a nutrient
regeneration dominated time period. We then
performed dark remineralization incubations to
assess changes in bacterial growth rate, DOM
bioavailablity and potential changes in bacterial
community structure.
1. UCSB Marine Science Interdepartmental Graduate
Program
DOM Remineralization in the Dark
DOM Production in the Light
Figure 4 . Fragment length patterns for initial
and final time points of the remineralization
experiment.
Figure 3. Bacterial abundance derived from
varying DOM Produced in the light experiment.

Conclusions Direct release and grazer mediated
release of DOM had differing effects on bacterial
growth rate and community structure. The higher
growth rates for the grazer and direct released
DOM treatments indicate an increase in
bioavailablity to bacteria. The DOM produced by
the zero virus (direct release) and control
treatments possibly caused an observed shift in
bacterial community structure in those
treatments. We did not observe significant
community structure shift within the grazer
treatment however different restriction enzymes
may yield higher resolution.
Figure1. Bacterial abundance in the light
experiment
Table 1. The change in cell numbers during the
log phase of growth and growth rate for each
treatment in the remineralization dark
incubations.
Figure 2. Bacterial production in the light
experiments.