These are small crustaceans. They’re hard-shelled ocean-dwelling animals that are relatives of lobsters, crabs and shrimp. Krill feed on phytoplankton — tiny algae that make energy from sunlight. In turn, krill are dinner for whales, seals, penguins, squid and fish.
What krill lack in size, they make up for in numbers. For example, a single Antarctic krill (Euphausia superba) is only around 6 centimeters (2.4 inches) long. But these krill live in huge swarms — so huge that scientists think there might be 500 million metric tons of Antarctic krill in the sea. That’s equivalent to the weight of some 5 million blue whales (which, by the way, dine on krill).
In a sentence
Swarms of krill move so much water when they swim that they help to stir up nutrients in the ocean.