Virginia Institute of Marine Science
MARINE ECOLOGY PROGRESS SERIES
Bacterioplankton abundance and production were examined over the course of a destratification event in the lower James River, Virginia, USA, Goals of the study were to determine if destratification would influence temporal patterns of bacterioplankton parameters and relationships between bacterioplankton and other biological and abiological parameters. Mean bacterial abundance grouped over stations did not change over the course of the study, and were characterized by much smaller coefficients of variation than all other planktonic constituents. However, bacterial production measured by H-3-thymidine (H-3-Tdr) incorporation decreased significantly from a stratified (324 mu g Cl-1 d(-1)) to a destratified (187 mu g Cl-1 d(-1)) hydrography. The importance of bacterial-autotrophic coupling was also suggested from oxygen metabolism experiments, which indicated substrate limitation of bacteria, and the existence of a rapidly utilized photosynthetically produced substrate. Correlative relationships between bacterial parameters with chlorophyll a were significant during stratified hydrography, but diminished or became non-significant during destratified hydrography. Estimates of microzooplankton grazing rates upon bacteria decreased significantly during the onset of destratification. During the stratified hydrography, bacterial parameters displayed highly significant negative correlations to ammonium, however these relationships disappeared during the destratified hydrography. Results of this study indicate that destratification changes the trophic interactions of bacteria within the microbial loop, however these changes are not necessarily reflected by temporal patterns of bacterial abundance.
BACTERIOPLANKTON; HETEROTROPHIC FLAGELLATES; HYDROGRAPHY; NUTRIENTS; SUBSTRATE; THYMIDINE INCORPORATION
Koepfler, ET; Kator, HI; Wetzel, RL; and HAAS, LW, Spatial and temporal bacterioplankton dynamics during destratification of the James River estuary, Virginia, USA (1993). MARINE ECOLOGY PROGRESS SERIES, 102, 229-244.