planktivore

A planktivore is an organism whose primary diet consists of plankton, including phytoplankton (photosynthetic microorganisms) and zooplankton (animal plankton). Plankton are typically small and drift with currents, and planktivores capture these organisms through various feeding strategies, such as filter feeding, suction feeding, ram suspension feeding, or gulping volumes of water and extracting prey.

In the animal kingdom, planktivory is widespread across taxa. Prominent examples include pelagic fish such as herrings, sardines, anchovies, and capelin, which feed on zooplankton and sometimes small crustaceans. Baleen whales, including blue and humpback whales, are classic planktivores that filter krill and other planktonic organisms from seawater. Among invertebrates, certain jellyfish and small crustaceans rely on plankton as a primary food source. Some seabirds also depend heavily on planktonic prey captured near the surface or within productive zones.

Adaptations for planktivory vary by lineage. Fish often possess gill rakers and specialized mouths that efficiently filter or trap plankton as water passes over the gills. Baleen whales use baleen plates to filter small organisms from large volumes of water. Invertebrates and seabirds may exhibit surface-feeding techniques or other morphological specializations that enhance plankton capture. Planktivores typically occupy lower trophic levels and serve as critical links transferring energy from primary production to higher trophic levels.

Distribution and ecological role: Planktivores are common in productive aquatic environments, including coastal areas, estuaries, upwelling zones, and open-ocean fronts. They respond to fluctuations in plankton production driven by changes in nutrients, climate, and oceanography, and they can be vulnerable to shifts in plankton communities and to fishing pressures targeting forage species.