planktivores

Planktivores are animals whose diets consist largely of plankton, tiny organisms that drift or float in the water column. Plankton spans both phytoplankton (microscopic plants) and zooplankton (small animals and micro-arthropods). Planktivory is common in marine and freshwater ecosystems and represents a key feeding strategy that channels energy from primary production to higher trophic levels.

Feeding modes among planktivores are diverse. Filter feeders, such as baleen whales, certain small pelagic fishes (for example, herring, anchovy, and sardine), and many invertebrates, strain plankton from the water using specialized structures. Suction and ram feeders actively draw in water and prey, often using vortices or specialized mouthparts to capture plankton. Some birds, including flamingos, grebes, and certain auklets, employ filter or surface-skimming feeding to harvest zooplankton and small crustaceans directly from the water.

Ecologically, planktivores occupy a central position in aquatic food webs by transferring energy from phytoplankton and zooplankton up to larger fish, mammals, and birds. Their populations respond to changes in plankton communities driven by nutrient availability, light, temperature, and ocean currents. Because plankton is highly sensitive to climate and environmental change, planktivores can serve as indicators of ecosystem productivity and health.

Adaptations that support planktivory include specialized filtering apparatus such as baleen plates and gill rakers, streamlined bodies for efficient grazing or suction, and sensory or behavioral strategies like schooling to increase encounter rates with prey. Human activities, including fishing pressure on planktivorous fish and climate-related shifts in plankton, can influence planktivore communities and their ecological roles.