Krill swarm in vast numbers in cold polar seas and feed many larger animals.

The longer version

Cold polar waters sustain enormous standing crops because seasonal ice and long summer daylight drive dense algal growth. Grazers able to harvest it gather in swarms stretching over great distances, drawing predators upward through the entire food web.

Fine combs on the front limbs sieve particles from passing water while swimming legs beat in unison. Many descend by day and rise after dark, avoiding visual hunters and carrying carbon downward. Oil-rich bodies make energy-dense meals for fish, squid, seabirds and filter-feeding whales, so abundance here supports life far beyond the animals themselves. Their numbers also rise and fall sharply from year to year with the condition of the ice.

Where this entry sits

Oceans and Sea Life looks at the salt water that covers most of the planet, from crashing waves and tides to the darkest deep-sea trenches. Expect notes on coral, fish, whales, sharks, jellyfish, shells, and the strange creatures that live far below the surface. The full list sits on the Oceans and Sea Life page, where every entry is listed in order.