Beneath Arctic ice, scientists find an ecosystem never imagined (+video)

Scientists have discovered a vast pea-soup-green bloom of tiny plant-like marine organisms under Arctic Ocean ice. The bloom represents an enormous, and until now, unknown reservoir of food for marine life in frigid waters at the top of the world.

These waters, in sum, appear to be far more biologically productive than previously believed.

"This wasn't just any phytoplankton bloom," says Kevin Arrigo, a Stanford University marine scientist and lead author of the study. "It was literally the most intense phytoplankton bloom I've ever seen in my 25 years of doing this type of research" in oceans around the world.

The scientists sampled only a relatively small section of ice above the Arctic basin's continental shelves last summer. But the findings suggest that, where the mix of nutrients and sunlight are right, other areas around the basin could be highly productive as well, the researchers say.

The discovery could help explain why previous groups observing open water concluded that the region wasn't hot spot of biological productivity. And it could explain how the ocean has been absorbing larger quantities of carbon dioxide (CO2) from the atmosphere than data could verify, the researchers suggest.

A report on the results from a research cruise aboard the US Coast Guard Ice Breaker Healy last June and July appears in the June 8 issue of the journal Science. The two-year project, known as ICESCAPE, was funded by NASA.

In general, much of what's known about activity at the bottom of the marine food chain in the Arctic has been learned by studying what's happening in open water. That is partly because researchers tend to visit the Arctic in the summer, when sea ice retreats and exposes more open ocean. Moreover, satellites that can measure phytoplankton levels also can't detect what's happening under the ice. 

But science, too, suggested that open water was the place to look. Phytoplankton need light, and historically, summer sea ice was thick and – at least early in the melt season – topped with a thick layer of snow. Less than 1 percent of the sunlight hitting the surface made it to the ocean surface underneath, says Don Perovich, a geophysicist at the US Army Corps of Engineers' Cold Regions Research and Engineering Laboratory in Hanover, N.H.

But when the ice breaker turned from the open water of the Chukchi Sea, north of Alaska, and headed into the ice, something unexpected happened.

"I was sure that phytoplankton abundance would drop like a rock," Dr. Arrigo recalls. 

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