How do planktonic crustaceans support fish, seabirds, and whales?

Planktonic crustaceans, such as copepods and krill, are essential components of marine food chains that support a wide array of larger animals. These arthropods graze on microscopic plants and, in turn, serve as a primary food source for fish, seabirds, and whales.123

• Whales: Large species, such as blue whales and fin whales, rely heavily on krill. These whales use baleen plates to filter vast quantities of these small crustaceans from the water, which fuels their impressive growth.43
• Fish: Many commercially important fish species depend on copepods and krill either directly or indirectly as a vital source of nutrition. For example, the copepod Calanus finmarchicus is a key food source for herring.23
• Seabirds: Various seabirds, including terns and alcids (such as puffins and auklets), feed on planktonic crustaceans. Some species, like the sheathbill, include crustaceans as part of a varied diet in Antarctic regions.5