PARAPHYSOMONAS IMPERFORATA (PROTISTA, CHRYSOMONADIDA) UNDER DIFFERENTTURBULENCE LEVELS - FEEDING, PHYSIOLOGY AND ENERGETICS

Ingestion rates of Paraphysomonas imperforata Lucas feeding on bacteri a were studied under a range of turbulence intensities. Turbulence had no effect on per cell ingestion rates of flagellates either upon init ial exposure to turbulent conditions or after 12 h under the turbulenc e treatment. Flagellates increased in numbers and decreased in size al all turbulence intensities as well as in non-turbulence treatments, p robably as an adaptation to an environment with lower food concentrati on than the stock cultures. Flagellates under high turbulence (ca 15 c m(2) s(-3)) were significantly smaller and more abundant after 12 h th an in the non-turbulence treatment. Total grazing on the bacterial pop ulation is thus implied to be higher under high turbulence. Flagellate gross growth efficiencies were not statistically different between th e turbulence treatments and their non-turbulent controls. When the res ponses to turbulence are compared to those for calanoid copepods some similarities can be seen (decrease in size and faster development time s).