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Sea-ice Biology

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.


Sea Ice as Habitat

In the harshness of the Arctic and Antarctic, simply surviving is a massive achievement. Here you’ll learn what challenges marine organisms have to overcome and how they manage to create a highly complex ecosystem in such an extreme habitat.


Biomass Production

Especially the availability of sunlight and food, which is subject to considerable seasonal variation, determines how much biomass – the basis of the food chain – ice algae can produce. Here you’ll learn how the algae cope with these changing conditions.


Sea-ice Organisms

The polar regions are extremely hostile for human life. Yet a broad range of adapted plants and animals have learned to defy the cold and seemingly endless dark of the winter ice. We’ll introduce you to the most important species.



Sea ice contains various nutrients, trace elements and climate-relevant gases, transports them across the ocean via sea-ice drift, and releases them into the water when it melts. In this way, iron released from the ice can produce algae blooms in iron-poor waters.


Use by Humans

Today, humans are using the polar regions more intensively than ever before: vast quantities of fish and krill are harvested, while tens of thousands of tourists visit them on cruise ships each year. Further, untapped oil and gas reservoirs have sparked new ambitions.


Sea-ice Ecosystems Under Climate Change

Especially in the Arctic, sea ice is dwindling in response to global warming. Both its total area and thickness are in decline. For those plants and animals that use the sea ice as a food source, safe haven or nursery, times are getting tougher.