September 14, 2012
Arctic Crustaceans Survive Ice Melt By Migrating Via Deep Ocean Currents
Brett Smith for redOrbit.com - Your Universe Online
As climate change tightens its grip on the polar regions, many biologists are investigating how different species that live there are being affected by increasing temperatures and decreasing polar ice.Some arctic crustaceans are showing why they have persisted for millions of years by adapting to the changes in their environment, according to a new report published in the journal Biology Letters by an international team of scientists.
“Our findings provide a basic new understanding of the adaptations and biology of the ice-associated organisms within the Arctic Ocean,” said study co-author Mark Moline, an oceanographer at the University of Delaware. “They also may ultimately change the perception of ice fauna as imminently threatened by the predicted disappearance of perennial sea ice.”
Moline, along with several scientists from Norway, found evidence of amphipods that resemble small shrimp, known as Apherusa glacialis, migrating along deep ocean currents and back to colder areas when the ice the live on, in the Fram Strait off the coast of Greenland, recedes during the warmer months.
According to the report, this behavior increases the survival rate of these crustaceans during warm polar summers and allows them to retake the sea ice as it reforms. This behavior is most likely an evolutionary adaptation that has developed over the millennia as the global climate fluctuated, the report added.
The scientists casually dubbed this observed behavior the “Nemo hypothesis,” a reference to the Disney animated movie Finding Nemo in which Nemo´s father rides deep-ocean currents for speedy transportation. The Arctic crustaceans in the study were found to detach from melting sea ice and dive into the deep waters of the Gulf Stream System that propels them back into the colder polar waters in the Arctic Ocean.
Researchers also measured the fat content of A. glacialis collected from the ice and found that their energy stores are sufficient to complete the return passage to the central Arctic after inhabiting the deep ocean current. This analysis provides further evidence that the crustaceans are well-equipped for these lengthy migrations that take place during the summer months.
“Through the Nemo hypothesis, we offer a new and exciting perspective that, although still based on a limited dataset, might change our perception of the ice-associated organisms and their future in an Arctic Ocean potentially void of summer sea ice within the next few decades,” said JÃ¸rgen Berge of the University of TromsÃ¸ in Norway.
These creatures have been previously caught in deep-current plankton nets during the polar night, but it was thought that their presence there was simply a result of the melting that passively exported them out of the Fram Strait and condemned them to a nomadic existence after the loss of their key habitat.
The scientists involved in the study said they hope these findings translate into the survival of the ice-associated organisms as their icy habitat is annually reduced by up to 80 percent during the polar summer and is expected to be under threat as the average global temperature rises.
“We believe that this is an important contribution towards a more comprehensive understanding of potential consequences of a continued warming of the Arctic and the predicted loss of summer sea ice,” Berge said.