Which of the world’s oceans would you guess is the most biologically productive? Would you guess a tropical ocean? Would you be surprised to find out it is the Antarctic Ocean? The water surrounding Antarctica accounts for only five percent of the world’s sea water, but produces twenty percent of the world’s sea life (measured by weight). Antarctic waters yield six times more life per square meter of surface area than the average yield of the other oceans.
What makes the Antarctic Ocean so rich with life? There are three reasons: long hours of daylight in the Antarctic summer to help algae grow, turbulent waters that keep nutrients floating in the water where phytoplankton can reach them, and the very cold water.
Why is cold water more productive? Cold water can hold more dissolved oxygen than warm water. The levels of dissolved oxygen in Antarctic waters are so high that many fish have few or no red blood cells (the blood cells other animals, including humans, use to carry oxygen). Without red blood, the fish appear white or nearly colorless.
The high levels of dissolved oxygen in Antarctic waters allow as many as 35,000 krill (small crustaceans that look a little like shrimp) to swarm in one cubic meter of sea water. These high numbers of krill support the rest of the Antarctic food web, providing food either directly or indirectly for virtually all the other animals in Antarctica.