If you want to survive in the Arctic and Antarctic sea ice, you have to be able to endure extreme environmental conditions – frigid temperatures, massively varying salinity, blazing sun in summer and the seemingly endless dark of the polar winter. Yet many species have successfully adapted – in some cases with the aid of amazing tricks, like the “antifreeze” glycoproteins produced by some polar fishes. Today, these highly specialised marine organisms – from the smallest single-celled organisms to massive whales – form a complex food web, one in which various predator-and-prey relationships mean the survival of one depends on the wellbeing of the other. At level 1 of the food pyramid, on the underside of the ice, countless tiny algae use sunlight to produce biomass. At level 2, small copepods and krill, which live in the ocean below the ice, feed on that biomass. At level 3, these organisms are eaten by fishes, which in turn become prey to seals, birds and whales at level 4. Of course, the reality is far more complicated than this simplified model. Nevertheless, the pyramid clearly shows how every species – no matter how small – has its own unique and essential role in the great symphony of sea-ice organisms. And that, if it were to be lost, it would have consequences for all polar species.
In this section, you’ll learn how this biological symphony works. We’ll show you the greatest challenges of living in the ice and corresponding survival strategies. We’ll also introduce you to the most important sea-ice organisms – which naturally include penguins and polar bears.