Nutrient cycling in a microflagellate food chain: II. Population dynamics and carbon cycling

Abstract

Carbon cycling in a 3-member food web containing a diatom (Phaeodactylum tricornutum bacteria, and a herbivorous/bacterivorous microflagellate (Paraphysomonas imperforata was examined. Ingestion of prey by the microflagellate was the primary mechanism for remineralization of particulate organic material. Approximately 65% of the particulate organic carbon (POC) initially present was lost over the course of the 8 d experiments in cultures containing microflagellates. No significant increase in remineralization was observed when bacteria were present. Bacteria were responsible for the uptake of dissolved organic carbon (DOC), but their overall contribution to carbon cycling was small relative to that of the microflagellate. Microflagellates incorporated diatom and bacterial biomass with equal efficiency (44%) during exponential growth.