Megafauna such as polar bears and walruses depend on sea ice to survive, but so do less visible animals. Amphipods, tiny crustaceans that look like a cross between shrimp and fleas, are one example.
Ice-dependent amphipods spend their lives clinging to the underside of sea ice, chomping on algae that grow there.
Norwegian marine biologist Jørgen Berge of the University Centre in Svalbard and his colleagues collected the most abundant of these ice-loving amphipods, a dark-eyed, transparent species called Apherusa glacialis, in plankton nets in January. They found the shrimp-like crustaceans at depths between about 650 and 6,500 feet (200 to 2,000 meters).
About half of the haul was made up of egg-bearing females -- an unusual find for researchers, who don't normally take samples of these winter-breeding species in January. (Few people brave Arctic winters even in the name of science.)
Global warming adaptation?
The discovery of deep-dwelling A. glacialis prompted Berge and his colleagues to come up with a theory of how these creatures manage to stay on ice despite seasonal melting. As the sea ice moves out into the oceans, they suggest, the amphipods ride along. When they get far enough out, the crustaceans drop down to depth. Between 650 feet and about 3,000 feet (200 and 900 m) below the ocean surface, the amphipods find themselves caught up in currents that actually move toward shore instead of away. These currents could provide a passive way for the amphipods to float back to ice-covered climes.