A snow-covered mountains looms over a bay with pancake ice

Sea ice is more than a hunting platform for polar bears--it forms the basis of the polar bear's food chain, starting with tiny algae inside the ice.

© BJ Kirschhoffer/Polar Bears International

11/15/2018 7:56:28 PM

It’s the Little Things: from Ice Algae to Polar Bears

By Jody Reimer, University of Alberta

“You need to let the little things that would ordinarily bore you suddenly thrill you.” — Andy Warhol

If you’re reading this, it’s probably because you love polar bears. Who doesn’t? They’re easy to love. The result of eons of evolution, polar bears possess a seemingly endless set of cool adaptations to their environment: hollow hair for extra insulation; grippy pads on the bottom of their feet for walking on ice; and, of course, the elegant white color for camouflage while hunting.

A few years ago, because of my desire to learn more about polar bears, I signed up to take a course called “Ecosystems in Ice-Covered Waters” being taught in Svalbard, Norway—an area known for polar bears. You can imagine my disappointment when I found out that I was to spend most of the course studying not these “Kings of the Arctic,” but the thin layer of brown algae you might find on the bottom of the sea ice! I don’t think anyone has ever described those single-celled algal organisms with the language of nobility.

What I was surprised to learn, however, is that if you think polar bears are cool, ice algae will blow your mind.

When salt water freezes, it creates ice that is quite a different material than the freshwater ice you might put in your iced tea. Rather than a solid, clear substance, sea ice looks kind of “cloudy.” When salt water freezes, all the salt is pushed out of the newly formed ice and into little pockets, where it often gets trapped. These little pockets of super salty water are called brine channels, and they create an intricate network of connected passageways and chambers within the sea ice, making the ice appear cloudy. These tiny brine channels are the perfect environment for single celled organisms—ice algae—to grow, since things that like to eat these algae are often too big to get inside these tiny passageways.

However, living inside sea ice is no easy task. The brine channels have a very high concentration of salt, which is constantly changing in response to the temperature. If you’ve ever tried to float in the Dead Sea, you’ll know that very salty water is much denser than fresh water, and you can imagine that the pressure that the salt water puts on these tiny cells can change a lot when the salt levels change.

The more I learn about ice algae, the more amazed I am by how they have adapted to live in this very extreme environment in ways that often seem like something out of a science fiction novel.

Ice algae are one of the key ways that the Arctic marine ecosystem turns sunlight into sugars, helping to form the basis of the food web. Ice algae provide high quality food (and in the Arctic, high quality food = high fat) for zooplankton, that can then provide food for fish, that are food for seals, that are food for… wait for it… polar bears!

It turns out that all that slimy brown stuff under the ice is both fascinating in its own right, living in one of the most extreme environments on Earth—inside ice!—and is also an important driver of the whole Arctic ecosystem, all the way up to polar bears.

Graphic of the polar bear's food chain

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