Protists are diverse group of organisms that exists in nature and are potential food for other organisms such as animals, bacteria or even protists themselves can eat each other.
Some algae are edible for human consumption. At some extent, blue whales have protist diet from group of planktons present in the ocean. Some molluscs also eat protists as part of their plankton diet as well. Other protists eat some protist by engulfing them (phagocytosis) and others can paralyze bacteria upon absorption.