Friday, February 15, 2013

Thinning ice is turning arctic into an algae hotspot

by Lauren Morello

Shrinking, thinning Arctic sea ice appears to be accelerating the growth of algae in polar waters, a new study finds, a development that could alter the region’s ability to absorb carbon from the atmosphere.
Scientists cruising central Arctic waters last summer aboard the research ship Polarstern were stunned to discover dense, shaggy deposits of the algae Melosira arctica clinging to the bottom of sea ice.
Though researchers all the way back to 19th-century Norwegian explorer Fridtjof Nansen had noted colonies of Melosira hanging under the ice, they had always assumed the algae prospered in areas covered by thick “multi-year” ice that had survived several summer melt seasons.
That wasn’t the case last summer. The Polarstern crew found large clumps of the algae growing in areas covered by ice that was just 3 feet thick, not 10.
Stranger still, when the researchers sent high-powered cameras to the ocean floor — using a small, unmanned robot and other equipment — they found it blanketed with lush green clumps of algae.
“I was shocked when I sat there on board the ship and these images came up,” said the new study’s lead author, Antje Boetius, a biological oceanographer at the Alfred Wegener Institute for Polar and Marine Research in Germany. “I was really screaming. Even the captain came down to look at what was going on. The sailors said, ‘How is it possible that the sea floor is green?’ ”
The research, published Thursday in Science, adds to a small but growing body of evidence that suggests the ongoing decline of Arctic sea ice is changing life in polar waters.
A significant increase in the growth of oceanic plants like algae could pull more carbon dioxide from the atmosphere, and ultimately trap it in the deep ocean as larger organisms eat those plants, or they decay and sink to deep water.

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