Protistan Feeding and Feeding rates
(^) Since about 1985 – surprisingly late – we have been aware of the importance of
heterotrophic protists (a term now generally preferred over protozoa) in marine
pelagic habitats. They have been shown to consume a larger fraction of algal
production than do mesozooplankton, so they constitute a major pathway in the
marine food web. Protists are relatively more important in oceanic than in neritic
habitats, although abundant and active in both. The delay was occasioned by (i) the
intense interest generated by larger grazers, and (ii) the fragility and transparency of
oceanic protists. The most-abundant planktonic microheterotrophs are small
flagellates. The swimming behavior and feeding mechanisms of these animals are
dominated by the properties of viscous flow and by boundary-layer processes. Protists
search for food particles using clues from water motion (in the viscous regime of the