Abstract
We studied planktonic bacterial population dynamics in response to the changing environment in a coastal system during an observation period of over 5 years using fluorescence in situ hybridization. To estimate the environmental constraint on the bacterial community, we focused on temperature, salinity, abundance of photoplankton (chlorophyll a), and dissolved organic carbon (DOC). The total number of bacteria (TDC) amounted to 3.0×105 to 5.0×106 cells mL-1, with 1.0×105 to 1.0×106 cells mL-1 for Bacteria, accounting for 11.8 to 74.8% of TDC, and 1.0×104 to 1.0×105 cells mL-1 for Gammaproteobacteria, 1.0 to 20.8% of TDC. The abundance of Archaea, which contributed from 0.1 to 12% to TDC, ranged from 2.0×103 to 3.0×104 cells mL-1. We found a positive relationship between environmental parameters such as temperature, salinity, chlorophyll a, and DOC and the abundance of total bacteria and Bacteria. The number of Gammaproteobacteria correlated with temperature, salinity, and chlorophyll a, but not with DOC. We suggest that increasing the temperature under eutrophic conditions will lead to high bacterial abundance and probably a change in the bacterial community.
