摘要：Enclosure experiments were performed in a eutrophic lake in order to evaluate the effects of filter-feeding fish (silver carp) on production of planktonic protozoa and the carbon flux from protozoa to zooplankton. The densities of heterotrophic nanoflagellates (HNF) and ciliates (94 μm. Grazing rates on ciliates were not different between treatments or between the two size groups of predators. Estimates of the ratio of zooplankton grazing rate on protozoan to zooplankton ingestion rate, indicated that both HNF and ciliates were more important food sources for zooplankton in enclosures with fish than in fishless enclosures. In the presence of fish, zooplankton depended almost exclusively on HNF for food, but in the absence of fish, zooplankton feeding shifted to phytoplankton. The introduction of silver carp to this eutrophic ecosystem changed the pathways of carbon flow from protozoan to zooplankton in the microbial food web.
