Sea ice: an important food source for young Antarctic krill

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Sea ice: an important food source for young Antarctic krill

Published on
September 29, 2017

Researchers from Wageningen Marine Research and the Alfred Wegener Institute (Germany) published two studies on food sources for Antarctic krill during the winter months in the Southern Ocean. The krill, caught with a under-ice net (SUIT-Surface and Under Ice Trawl), are an important part of the Antarctic food chain.

Krill diet

Investigation of the stomach contents of young krill showed that, during winter, they mainly feed on organisms that are found in the sea-ice. Their diet consisted mainly of algae, but also other organisms were found. There were, for instance, remains of the relatively large copepods present in the stomachs.

A detailed analysis showed that the diet of young krill was dependent on environmental factors. Further analyses of fatty acids and stable isotopes showed that up to almost 90% of the carbon in the body of krill larvae originated from sea-ice algae, which they accumulated by eating them. This percentage decreased when the krill grew older.

Organisms found in the stomach of young krill. Top: a centric and a pennate diatom (algae). Bottom: a foraminifer and the shell of a tintinnid, which both are unicellular organisms.
Organisms found in the stomach of young krill. Top: a centric and a pennate diatom (algae). Bottom: a foraminifer and the shell of a tintinnid, which both are unicellular organisms.

Results and importance

The studies show that krill are strongly dependent on sea ice for their food during their first winter; that their diet varies depending on certain properties of the sea-ice habitat; and that the dependence on sea-ice food sources is less for krill over one year old.

These results are important for gaining insight in the role of sea-ice in the Antarctic food chain, and in the survival of krill during a period of food scarcity. This information can be helpful for policy-making for a sustainable krill fishery, as well as for predicting potential consequences of climate change.