Planktonic organisms that can be classified at several trophic levels. For example, some ciliates can be photosynthetic but also can ingest other.

Traditionally, marine protist plankton were considered to be either “microzooplankton” (which eat) or “phytoplankton” (which cannot eat, but only photosynthesize). Mixotrophic protist plankton – mixoplankton – are single-celled organisms that can both eat and photosynthesize, in their one cell. Dismissed as of minor consequence by mainstream marine science for over a century, we now know that most “phytoplankton” and 50% of the “microzooplankton” in the upper ocean are mixotrophic.