Antarctic
peninsula
Krill are the engine that powers the Antarctic ecosystem. They are small semi-transparent crustaceous, few centimetre long, that form, together with other animals the zoo-plankton.
Krill are in a very “strategic” position in the Antarctic food chain; they feed on microscopic phytoplankton and form the base food for big animals such as seals, penguins, whales and sea birds.
Krill are also fished as human food; in Japan dried krill are called okiami and are commonly on sale. Krill oil is now commercialised as a natural source of Omega-3.
Krill and ice
Recent studies (November 2004) have shown that stocks of krill in Antarctica have declined dramatically in recent years. The reason is likely to be a fall in the amount of sea ice in winter months especially in the Antarctic peninsula region. Relatively warm winters favour the development of salps, a barrel-shaped, free-floating tunicate which feeds on phytoplankton and therefore represent the most important competitor of krill. This complex relation is being demonstrated with the analysis of 30 years long series of satellite data on ice cap extension.
Polynyas
Polynyas are regions of well mixed ice free water created by strong off-shore katabatic winds. Being exposed to sunshine, polynyas teem with phytoplankton and therefore a dynamic food web is found in these regions with enormous abundances of krill.
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image (58 KB) Small polynya areas on the lee side
of the three Balleny islands
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image (218 KB), Spring phytoplankton blooming
around Candlemas and Vindication islands, in the south Sandwich archipelago,
north of Antarctic peninsula
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