Dobbs, F. F. Dept. Ocean, Earth and Atmospheric Sciences / Old Dominion University, fdobbs@odu.edu
Choi, K. KH. Dept. Ocean, Earth and Atmospheric Sciences / Old Dominion University, kchoi@odu.edu

 
LONG-TERM VARIATION IN SOLE-CARBON SOURCE UTILIZATION BY BACTERIOPLANKTON IN LOWER CHESAPEAKE BAY
 
Since 1996, bacterioplankton samples have been taken monthly along a hydrographic transect across the entrance to Chesapeake Bay (see abstract by Choi et al.). At three stations, samples of surface and bottom water were collected and inoculated into Biolog GN microtiter plates. In general, substrate utilization i.e., color development, was greater in bottom-water samples than in surface-water samples. There was some suggestion of interannual differences in substrate utilization. Nonetheless, principal components analysis of appropriately transformed data indicated no patterns of sole-carbon source utilization, either across the transect or through time. Instead, nearly all samples occupied a single cluster in two-dimensional principal-component space, where PC1 and PC2 accounted for 75% of the variance in the data. We propose three possible explanations for this result. First, there are no seasonally distinct populations of heterotrophic bacteria in lower Chesapeake Bay. Second, given our protocol of a standard incubation temperature, competitive dominance by relatively few heterotrophic populations masks any temporal changes in other populations. Third, there is a commonality in utilization; no matter which suite of populations is present, they utilize the substrates in a similar manner. Tests of these hypotheses are underway.
 
Day: Thursday, Feb. 4
Time:
Location: Sweeney Center
 
Code: CS57TH0465S