Effects of small-scale turbulence on microzooplankton predator-prey interactions

Ptak, Marcianna (1998) Effects of small-scale turbulence on microzooplankton predator-prey interactions. Masters thesis, Memorial University of Newfoundland.

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Abstract

The biological and chemical processes which affect bacterioplankton growth and mortality have been well studied. Little is known about physical controls on microbial systems. Turbulent mixing can influence the rates of prey encounter and grazing characteristics of small metazoan grazers, however models suggest that small-scale turbulence (Kolmogorov length scale) should not have an effect on microorganisms less than 10 micrometers. Recent studies suggest that, despite theory, turbulent mixing can influence microflagellates. This study has examined the interactions between temperature (0°,5°,10°,15°C) and turbulent mixing on the growth and trophodynamics between the heterotrophic microflagellate Paraphysomonas imperforata and its bacterial prey, Vibrio splendidus. It was found that growth rates of P. imperforata at 5 to 15°C were 1.5 to 2 fold higher under turbulent compared to static conditions. However, as the temperature decreased from 15 to 0°C, ingestion and clearance rates increased 10 fold, but no significant difference was found between the turbulent and static conditions. It is believed that the increased growth rates in the flagellates at the warmer temperatures in the turbulent condition were due to increased encounter rates between the microflagellate and bacteria. The higher ingestion and clearance rates at the colder temperatures are believed to be due to the increase in the viscosity of seawater, allowing flagellates to move a greater volume of water across its boundary layer. These results suggest that growth and ingestion rates determined during static incubations of in situ samples under 15°C from previously published studies may be over or underestimated since turbulence is continuous in nature.

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