Bottom of the food chain at the bottom of the world

Australian scientists recently completed a mission studying algae and krill that live under Antarctic sea ice, in an effort to understand the workings of their ecosystem and how it may be affected by climate change.

The 2 month investigation was part of the international Sea Ice Physics and Ecosystem eXperiment-II, or SIPEX-II, and it took place onboard the icebreaker Aurora Australis – currently back in Antarctica on its never-ending mission to transport supplies and personnel to and from Australia’s Antarctic stations.

One part of the mission used an underwater robot called ROV – short for ‘Remotely Operated Vehicle’ – equipped with a light sensor to measure reductions in blue and green light beneath the ice, and hence estimate the amount of algae.

The other part involved capturing larval and juvenile krill and examining their metabolism, growth rate and diet. These tiny crustaceans go through 12 larval stages, about which not much is known as previous research has mostly focused on adults, and even then usually in the Antarctic summer rather than winter as experienced by SIPEX-II.

Krill feed on the sea ice algae, and are themselves food for larger animals like penguins, seals and whales. So together the krill and algae form the foundations of the Southern Ocean ecosystem.

Other members of SIPEX-II looked at different physical and biological aspects, such as ice and snow cover measured with laser and radar-equipped helicopters, algae physiology, sea ice biogeochemistry, and water temperature, oxygen content and salinity.

With climate change predicted to reduce sea ice by 35% by the end of this century, we need to know how the Antarctic ecosystem works so that we can understand the impact of losing its cover.

Find out more about this project on the website of the Australian Antarctic Division.

(This story aired on 13 December 2012 – you can listen to the podcast.)

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