Paraphysomonas imperforata (Protista, Chrysomonadida) under different turbulence levels: Feeding, physiology and energetics

Abstract

Ingestion rates of Paraphysomonas imperforata Lucas feeding on bacteria were studied under a range of turbulence intensities. Turbulence had no effect on per cell ingestion rates of flagellates either upon initial exposure to turbulent conditions or after 12 h under the turbulence treatment. Flagellates increased in numbers and decreased in size at all turbulence intensities as well as in non-turbulence treatments, probably as an adaptation to an environment with lower food concentration than the stock cultures. Flagellates under high turbulence (ca 15 cm2 s-3) were significantly smaller and more abundant after 12 h than in the non- turbulence treatment. Total grazing on the bacterial population is thus implied to be higher under high turbulence. Flagellate gross growth efficiencies were not statistically different between the turbulence treatments and their non- turbulent controls. When the responses to turbulence are compared to those for calanoid copepods some similarities can be seen (decrease in size and faster development times).