Influence of Turbulence on Bacterial Production in the Sea

The role of turbulence on heterotrophic bacterial production (BP) was tested in batch cultures in the laboratory and under in situ conditions. BP was significantly higher under stagnant conditions$(\thicksim 19%)$in the presence of particles such as phytoplankton. Turbulence in the upper mixed layer of the sea significantly altered in situ BP over a 14-d period. During calm periods, BP was significantly (P≤≤ 0.0025) higher in the stagnant treatment, while during a period of high turbulence, BP was not significantly (P = 0.13) different in either experimental treatment. In laboratory experiments, BP was higher under turbulent conditions (P = 0.064) after agitating seawater for 24 h, while in the undisturbed control, BP was significantly higher (P = 0.009) under stagnant conditions. Removing particles other than bacteria led to BP that was similar in both stagnant and turbulent treatments. Additions of glucose or leucine (100 μ M and 1 mM final concn) to seawater containing phytoplankton generally reduced the difference in BP between stagnant and turbulent conditions. Our results suggest that variations in turbulence modify bacterioplankton community structure in the upper layer of the sea.