Grazing, Growth, and Ammonium Excretion Rates of a Heterotrophic Microflagellate Fed with Four Species of Bacteria

Abstract

The population growth of a microflagellate, Monas sp., isolated from Lake Kinneret, Israel, was studied. The protozoan growth rates, rates of ingestion of bacteria [Chlorobium phaeobacteroides, Escherichia coli, Salmonella typhimurium and an unidentified bacterium] and final population yields generally increased with increasing bacterial concentrations, although the exact relationship varied depending on the species of bacteria used as food. Grazing rates decreased hyperbolically with increasing food density. Gross growth efficiencies and ammonia excretion rates were similar over a range of food densities among their spp. of bacteria. Population doubling times and ammonia excretion rates were lowest, and growth efficiencies were highest, at temperatures between 18.degree.-24.degree. C. Under optimum conditions, the microflagellates had average population doubling times of 5.0-7.8 h, average growth efficiencies of 23.7-48.7% and average ammonia excretion rates of 0.76-1.23 .mu.mol of NH4+ per mg (dry wt)/h.