It is a small, swimming crustacean that lives in large schools, called swarms, sometimes reaching densities of 10,000–30,000 animals per cubic metre.

[5] The main spawning season of Antarctic krill is from January to March, both above the continental shelf and also in the upper region of deep sea oceanic areas.

The gut forms a straight tube; its digestive efficiency is not very high and therefore a lot of carbon is still present in the feces.

In lower food concentrations, the feeding basket is pushed through the water for over half a metre in an opened position, and then the algae are combed to the mouth opening with special setae (bristles) on the inner side of the thoracopods.Antarctic krill can scrape off the green lawn of ice algae from the underside of pack ice.

[13][14] Krill have developed special rows of rake-like setae at the tips of their thoracopods, and graze the ice in a zig-zag fashion.

Recent discoveries have found that the film of ice algae is well developed over vast areas, often containing much more carbon than the whole water column below.

Krill are thought to undergo between one and three vertical migrations from mixed surface waters to depths of 100 m daily.

[15] The krill is a very untidy feeder, and it often spits out aggregates of phytoplankton (spitballs) containing thousands of cells sticking together.

If the phytoplankton is consumed by other components of the pelagic ecosystem, most of the carbon remains in the upper layers of the ocean.

There is speculation that this process is one of the largest biofeedback mechanisms of the planet, maybe the most sizable of all, driven by a gigantic biomass.

The function of these lights is not yet fully understood; some hypotheses have suggested they serve to compensate the krill's shadow so that they are not visible to predators from below; other speculations maintain that they play a significant role in mating or schooling at night.

[16] Krill use an escape reaction to evade predators, swimming backwards very quickly by flipping their rear ends.

Its content of repetitive DNA is about 70% and may reach up to 92.45% after additional repeat annotation, which is also the largest fraction known of any genome.

The gene and intron lengths of Antarctic krill are notably shorter than those of lungfishes and Mexican axolotl, two other animals with giant genomes.

This front runs roughly at 55° south; from there to the continent, the Southern Ocean covers 32 million square kilometres.

The krill swarms swim with these water masses, to establish one single stock all around Antarctica, with gene exchange over the whole area.

Currently, there is little knowledge of the precise migration patterns since individual krill cannot yet be tagged to track their movements.

Thus primary production—the conversion of sunlight into organic biomass, the foundation of the food chain—has an annual carbon fixation of 1–2 g/m2 in the open ocean.

A possible decline in Antarctic krill biomass may have been caused by the reduction of the pack ice zone due to global warming.

[27] Antarctic krill, especially in the early stages of development, seem to need the pack ice structures in order to have a fair chance of survival.

In the years of low pack ice conditions the krill tend to give way to salps,[28] a barrel-shaped free-floating filter feeder that also grazes on plankton.

[30][31] The further effects of ocean acidification on the krill life cycle however remains unclear but scientists fear that it could significantly impact on its distribution, abundance and survival.

When the full net is hauled out of the water, the organisms compress each other, resulting in great loss of the krill's liquids.

Its high protein and vitamin content makes krill quite suitable for both direct human consumption and the animal-feed industry.