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'Megabloom' of tiny plants under Arctic sea ice tied to climate change

Kathryn Hansen / NASA

Arctic melt ponds visited during a July 2011 expedition on the U.S. Coast Guard Cutter Healy gave scientists a chance to find "windows from the sky to the ocean" that are perfect for phytoplankton blooms.

Experts were shocked to find a thick, 60-mile-long "phytoplankton megabloom" under Arctic sea ice, announcing in a study Thursday that ice made thinner by warming temperatures has, for now at least, created ideal conditions for the microscopic, single-cell plants to flourish.

More blooms are likely hidden under the ice, making for "ecological shifts" in Arctic waters that favor some species over others since phytoplankton are the base of the marine food chain, Stanford professor and lead researcher Kevin Arrigo told msnbc.com.

Scientists had thought Arctic phytoplankton blooms only happened after sea ice melted in summer, so the discovery is "like finding the Amazon rainforest in the middle of the Mojave Desert," added Paula Bontempi, who manages the ocean biology program at NASA, which funded the research.


"The waters literally looked like pea soup," Arrigo said at a press conference announcing the study in the journal Science. "It was as thick as a 5-year-old child is tall."

The team discovered the bloom in July 2011 in thin sea ice pocketed with ponds of melted ice on the Chukchi Sea off northern Alaska. Arctic sea ice has been shrinking and thinning in summer since 1979, the result of warming temperatures over the region. 

Those melt ponds proved crucial, allowing just enough light to get the growth process started while also protecting the algae from ultraviolet radiation.

"They were the windows from the sky to the ocean," said researcher Don Perovic, an ice scientist with the U.S. Army Corps of Engineers.

"If I were a phytoplankton," Perovic added, "that's where I'd want to live."

Arrigo said in his 25 years of studying phytoplankton blooms he had never seen one this large. Blooms in open water are much smaller, he noted, while very thick ice won't allow any light in to start photosynthesis.

"It's going to be a more productive system," Arrigo said, noting that plankton bottom feeders will benefit as the plankton sinks to the bottom of the Chukchi, much of which is around 160 feet deep.

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The researchers didn't expect Arctic sea ice to disappear completely, since winters are still very cold, but they did note some potential downsides.

Some fish species that rely on mid-level nutrients will suffer, Arrigo said, and the bigger issue is that a warming Arctic appears to be triggering phytoplankton blooms earlier.

Species that can't adapt "to be there at the right time of year" will suffer, Arrigo said.

NASA funded the expedition as a way to match the satellite-based data it gathers on the Arctic with data gathered on the ice.

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