Scientists Say: Krill

These tiny critters play a big role in the ocean


This Northern krill is a tiny crustacean that swims in the ocean.

Øystein Paulsen/Wikimedia Commons/(cc-BY-SA 3.0)

Krill (noun, “KRIL”)

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.

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Bethany Brookshire was a longtime staff writer at Science News Explores and is the author of the book Pests: How Humans Create Animal Villains. She has a Ph.D. in physiology and pharmacology and likes to write about neuroscience, biology, climate and more. She thinks Porgs are an invasive species.

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