The emerald green waters of a polynya algae bloom in Antarctic sea ice. David Munroe, USAP /

By Christine Dell'Amore, National Geographic News
Published February 28, 2011

"Crazy green" pools teeming with life have been found among remote Antarctic sea ice, scientists say—and they may be a global warming boon.

Observed in the little-studied Amundsen Sea (see map), the brilliant blooms owe their colors to chlorophyll, a pigment in various types of phytoplankton, or tiny algae. Algae-eating zooplankton, small crustaceans called krill, and fish and shrimp larvae also thrive in the area.

A recent scientific expedition studied the blooms while plying the Amundsen Sea's polynya, a  region of seasonally open water surrounded by sea ice.

Often hundreds of miles wide, polynyas are nutrient-rich "oases" that offer refuges for animals big and small, according to Patricia Yager, chief scientist for the Amundsen Sea Polynya International Research Expedition (ASPIRE), which is funded by the U.S. National Science Foundation and the Swedish Polar Research Secretariat.

The open pockets occur for two reasons: because wind blows chunks of ice away from the coast, and because warm air or an upwelling of warmer water melts sections of ice away. (Related: "New Zealand Earthquake Spurs Giant Glacier Collapse.")

When summer sea ice melts, it can release micronutrients into the ocean that supercharge algae blooms. Micronutrients are trace amounts of elements, such as iron, that are essential for plant growth.

As glaciers and sea ice in western Antarctica begin to melt due to global warming, a greater influx of micronutrients may flow into the oceans and fuel bigger algae blooms, Yager said in an interview. …

The recent expedition—which took place from November to January aboard two research icebreakers—was among the first to sample the polynya firsthand.

Samples of the polynya's surface waters revealed the pools held as much as 45 micrograms of chlorophyll per liter. That's five times greener than parts of the Amazon River plume, the nutrient-rich region where the Amazon empties into the Atlantic.

Such a discovery "exceeds all expectations," Yager wrote in a preliminary research report.

It's "the greenest water I've seen in the world," she said.

It's not unusual to find high amounts of chlorophyll in the Amundsen Sea, according to Maria Vernet, a research biologist at Scripps Institution of Oceanography in La Jolla, California.

That's because polynyas' waters are regularly infused with fresh water from melting sea ice, and they receive plentiful sunlight—both fruitful conditions for life. For instance, algae often thrive in freshwater "lenses"—layeres of fresh water up to 130 feet (40 meters) deep that sometimes sit on top of denser seawater.

But "seeing something more than 30 [micrograms of chlorophyll] is exceptional, and seeing something more than 40 is very exceptional," said Vernet, who was not involved in the expedition. "I've only seen it a few times." …

"Crazy Green" Algae Pools Seen in Antarctic Sea



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