Smith, E. M. UMCES Horn Point Lab.,
Kemp, W. M. UMCES Horn Point Lab.,

Variations in bacterial community respiration have profound impacts on the overall carbon balance of aquatic ecosystems. Relatively little is know, however, about what factors may regulate these observed variations in respiration. This study attempts to relate changes in bulk respiration rates of bacterial assemblages to the activity of single cells within those assemblages, via the tetrazolium dye, CTC, and flow cytometric analysis. At three stations along the estuarine gradient of Chesapeake Bay, respiration rates and CTC activity were measured in a series of nutrient and carbon enrichment bioassays. Rates of respiration, and effects of nutrient vs. carbon additions, showed clear regional differences within the estuary. Overall, respiration rates were highly related to abundance of CTC-positive cells within the bacterial community, while unrelated to total bacterial abundance. Both cell-specific activity (fluorescence intensity) and cell size were also strongly related to respiration rates. These findings suggest that observed changes in respiration rates were the result of changes in the abundance and specific metabolism of a subset of highly active (CTC+) bacteria within the total bacterial assemblage. These cells tended to be larger, had higher cell-specific activities, and presumably accounted for the bulk of measured community respiration.
Day: Monday, Feb. 1
Time: 03:30 - 03:45pm
Location: Sweeney Center
Code: SS41MO0330S