Trophic Dynamics in Chesapeake Bay: Ecological and Biochemical Approaches to the Study of Flows of Carbon from Phytoplankton to Bacterioplankton

1. Particle-associated bacteria contributed cat 20% to overall production, although their numbers were proportionally lower, compared to free cells. As a first-order estimate, decomposition of particulate phytodetritus contributes about 20% of the total production, although the products of hydrolysis of the particles may help support the other 80%.
   
   
2. Growth rates of attached bacteria were similar to, or greater than, those of free cells. Production by attached cells in surface waters was particularly high in July in mid-Bay waters and near the mouth of the Bay. These results are surprising, and deserve further study.
   
   
3. During the summer period of highest bacterial production and abundance (June -August), production of attached bacteria contributed about 10% of the total in the mid-Bay, but absolute production levels were low for all bacteria in anoxic bottom waters. During this period of maximum stratification, particle decomposition is concentrated in warm, oxygenated surface waters.
   
   
4. During periods of bottom hypoxia and anoxia, the proportion of thymidine incorporated into DNA, relative to total thymidine incorporation, increased for bacteria in bottom waters, whereas in aerobic waters the proportion incorporated into DNA was similar for both surface and bottom samples. These patterns were unexpected, as previous results (McDonough et al., 1986) suggested the opposite in a monomictic lake in Georgia.