Nutrient cycling in a microflagellate food chain: I. Nitrogen dynamics

Abstract

The phagotrophic microflagellate Paraphysomonas imperforata was capable of grazing 2 marine phytoplankton species, the diatom Phaeodactylum tricornutum and the chlorophyte Dunaliella tertiolecta . The phytoplankton species, which are grossly different in size, shape and morphology, were first grown under different degrees of nitrogen and phosphorus limitation. Patterns of nutrient regeneration appeared to be a function of the physiological state of the prey. Because protozoa are able to convert prey nutrients to their own biomass with great efficiency during exponential growth, particularly when the prey are nutrient-limited, the size and complexity of the microbial food web may be related to the nutritional state of the phytoplankton.