Significance of predation by protists in aquatic microbial food webs |
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Authors: | Sherr Evelyn B Sherr Barry F |
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Institution: | (1) College of Oceanic and Atmospheric Sciences, Oregon State University, 104 Ocean Admin Bldg, Corvallis, OR 97331-5503, USA |
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Abstract: | Predation in aquatic microbial food webs is dominated by phagotrophic protists, yet these microorganisms are still understudied
compared to bacteria and phytoplankton. In pelagic ecosystems, predaceous protists are ubiquitous, range in size from 2 μm
flagellates to >100 μm ciliates and dinoflagellates, and exhibit a wide array of feeding strategies. Their trophic states
run the gamut from strictly phagotrophic, to mixotrophic: partly autotrophic and partly phagotrophic, to primarily autotrophic
but capable of phagotrophy. Protists are a major source of mortality for both heterotrophic and autotrophic bacteria. They
compete with herbivorous meso- and macro-zooplankton for all size classes of phytoplankton. Protist grazing may affect the
rate of organic sinking flux from the euphotic zone. Protist excretions are an important source of remineralized nutrients,
and of colloidal and dissolved trace metals such as iron, in aquatic systems. Work on predation by protists is being facilitated
by methodological advances, e.g., molecular genetic analysis of protistan diversity and application of flow cytometry to study
population growth and feeding rates. Examples of new research areas are studies of impact of protistan predation on the community
structure of prey assemblages and of chemical communication between predator and prey in microbial food webs.
This revised version was published online in August 2006 with corrections to the Cover Date. |
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Keywords: | bacterivory herbivory microbial food webs pelagic ecosystems phagotrophy protists |
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