krillRoger Tory Peterson has called penguins "the litmus paper of the sea." Many people use them to gauge the health of the southern oceans.

When there are low quantities of krill, adult penguins must forage longer to find enough food to eat, and penguin chicks may starve. In 1995, up to 50 chicks starved to death each day on one Antarctic island. The Adelie penguin chick die-off was blamed on a lack of krill. (This occurs several years after a bad ice season.)

Krill, small, shrimp-like creatures in the family Euphausiidae, are produced in large numbers during years of heavy sea ice cover. Why is that? Vast quantities of nutrients accumulate on the underside of sea ice in such density that the ice takes on a pinkish or greenish sheen. As the ice melts in the Antarctic spring, these nutrients are released into the water, providing essential nutrients to encourage phytoplankton growth.

When there is less ice, less nutrients fall into the water, less phytoplankton blooms, and fewer krill are produced. When the krill mature 4-5 years later, they are eaten by penguins. A low supply of krill causes hardship for penguins.

According to a Boston Sunday Globe article, "It's too early to tell whether the penguins are being affected by warmer temperatures or the ozone hole above Antarctica. So far, the population fluctuations may be normal."

How are sea ice cover and penguin chicks related?

  1. Discuss the Antarctic food chain consisting of the sun, phytoplankton, krill, penguin, baby penguin (parent regurgitates food for chick), and the Weddell seal. Something is disrupting this food chain.
  2. Read and discuss the Adelie penguin chick die-off article from the Boston Sunday Globe.
  3. Find Mawson Base and US Palmer Station, the areas mentioned where chicks were in trouble.
  4. Compare satellite images of sea ice cover of Antarctica for several years. Trace the extent of sea ice cover for several years onto tracing paper. Use a different colored pencil or overhead transparencies and grease pencils for each year. Make a key defining each years' data.
  5. See how ice cover corresponds to changes in Adelie penguin population for subsequent years.


  • satellite images from several years of ice cover in Antarctica
  • tracing paper
  • colored pencils
  • overhead transparencies
  • grease pencils