Planktivores primarily feed on plankton, which includes tiny organisms drifting in water, such as zooplankton and phytoplankton. These small, often microscopic, creatures serve as the main nutritional source for planktivorous species, including various fish, whales, and some types of crustaceans. Planktivores typically have adaptations, such as specialized gill structures or filter-feeding mechanisms, to efficiently capture and consume plankton as it flows through the water. This diet is crucial for their survival and plays a significant role in aquatic ecosystems, as it links the primary producers (like phytoplankton) to higher trophic levels.