Several species of krill, which are crustaceans related to shrimp, crayfish, and crabs, are abundant in all oceans on Earth.

Antarctic krill, which inhabit the southern oceans that completely surround icebound Antarctica, are 2.5 inches long — small in size, but big in their role near the bottom of numerous food chains in those waters.

Krill have several swimming legs to move forward, but they jet backward with a powerful forward flip of their rears to escape predators. They use comb-like front appendages as “baskets” to snare tiny food items from ocean water and have gills to take oxygen from that water.  

Scientists estimate there are over 379 million tons of Antarctic krill, and there are over 350 trillion individual Antarctic krill living in large swarms in ocean water under the Antarctic pack ice. Some gatherings of this kind of krill are so huge they can be seen from space.

As filter feeders, Antarctic krills’ front appendages collect free-floating phytoplankton (one-cell algae), zooplankton, and diatoms from the open ocean. Those tiny bits of food are then passed by the filters to the krills’ mouths.

This kind of krill also scrapes off and consumes the abundant green algae attached to the underside of the Antarctic pack ice on southern oceans. Sunlight shines through the ice, encouraging the growth of those algae.

A key species, krill are one of the largest biomasses on Earth because of their tremendously abundant food supplies. Therefore, krill are the main food of baleen whales, crab-eater seals, penguins, fish, squid, and other marine creatures around Antarctica.

Living exclusively on pack ice around beautiful and wild Antarctica, crab-eater seals are the most common seals in the world because of the overwhelming abundance of krill.

Dwelling in the Southern Hemisphere, Antarctic krill spawn from January to March. Each female produces up to 10,000 eggs, which male krill fertilize. Those eggs sink in the ocean, but the larvae swim to the surface after hatching and feed on microscopic plankton.

And like all crustaceans, krill must periodically shed their exoskeleton (outer shell) to be able to grow. They mature in two or three years and live up to six years, if not eaten.

Krill are important in the southern oceans for the number of marine creatures that ingest them. Krill annually produce one of the largest biomasses of wildlife on Earth. They turn plankton in the open ocean and algae under ice shelves into food (themselves) that larger marine creatures eat.

Oceans around intriguing Antarctica would be much poorer without Antarctic krill. They are near the base of several food chains of who eats whom.   


Clyde McMillan-Gamber is a retired Lancaster County Parks naturalist.

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