Antarctica's 'green snow' is sucking carbon out of the air

Antarctica's 'green snow' is sucking carbon out of the air

Photosynthesis and Antarctica. It might not be the most intuitive combination, but the frozen continent, famous for statuesque icebergs and marching penguins, is also home to communities of algae, mosses, lichens, and even some kind of flowering grass. A new study advanced on the so-called green snow.

They are rare, of course: less than one percent of the entire continent is permanently ice-free to begin with. And what land vegetation does exist must rely heavily on melting snow and ice for its water supply.

It's all part of a fragile ecosystem that scientists are eager to understand as global temperatures rise, affecting not only large Antarctic ice sheets but also the delicate balance of life there.

A team of scientists from the United Kingdom recently created the first large-scale map and estimate of the extent of green algae in the Antarctic Peninsula, a mountainous expanse that stretches more than 800 miles into South America and has experienced one of the fastest rates of warming in the world The results of the study, published in the journal Nature Communications, show that "green snow" is a major carbon sink for the continent, absorbing approximately 479 tons of carbon per year through the photosynthesis.

"On a global scale, carbon dioxide uptake is small, but at the same time extremely important for Antarctica," says Matt Davey, who led the study by researchers from the University of Cambridge and the British Antarctic Survey. Tonnage, he adds, is roughly equivalent to the amount of carbon emitted by 875,000 car trips averaging 10 miles per trip.

The amount of carbon uptake from Antarctic algal blooms, which come in green, red and orange varieties that can make the snow where they live appear colored, is likely to be much higher, says Davey, as scientists get a more complete picture of its total biomass across the continent.

Photosynthetic life in Antarctica also includes those mosses, lichens, and two flowering plants (Antarctic hair grass and Antarctic mustard), which further contribute to total carbon uptake.

Algal communities tend to be relatively abundant along the coast of the Antarctic Peninsula during the southern summer months of December through February, when the average temperature is just above freezing. The green algae included in the study favor wet, muddy snow because microorganisms need liquid water to reproduce, Davey says. They also thrive near penguin colonies, bird nesting sites, and seal hangouts, as animal poop provides nutritious nitrogen and phosphate for flowers.

To achieve greater precision in their results, the scientists supplemented the data from the European Space Agency's Sentinel 2 satellite with measurements from the field. Information from the satellite, which measures specific wavelengths of light reflected off the Antarctic surface, could be hampered by cloud cover and false signals that could be misinterpreted as green algae, says Andrew Gray, lead author of the paper.

The researchers also invited citizen scientists to submit photographs of algal blooms taken over several summers. "It's great information for us because we can't be everywhere," says Davey, who recently started a new position at the Scottish Association for Marine Sciences in Oban.

Red and orange algae were excluded from the study because they have pigments that can interfere with the satellite, says Gray, a researcher at the University of Cambridge and the NERC Field Spectroscopy Facility in Edinburgh. "There are red species and green species," he says. "But you also get green species that turn red in the same way that trees turn red in fall."

(The study notes that satellite-detected green blooms may include some red and orange cells, but their findings are based on readings for chlorophyll, a green pigment, and assumed that the blooms were predominantly green species.)

Gray and Davey say their future research goals include incorporating red algae blooms and eventually extending their mapping across Antarctica. They also want to better understand the life cycle and physiology of algae. Davey says, "The more we can understand about biology and physiology, the better we can understand the [broader] ecosystem."

A big question for scientists studying all types of vegetation in Antarctica is how its ecosystem will fare as higher temperatures invade this remote region of the planet. (In February, Brazilian scientists reported the highest temperature ever recorded in Antarctica: 20.75 degrees C, or nearly 70 degrees F.)

Current predictions predict an expansion in algal blooms and plant growth as thaws accelerate and new ground opens up. But, as in nature, there are a number of dynamic and interconnected factors. Among other things, the impact of climate change on penguins, birds, and seals can also affect the survival of algae, mosses and their brethren - intertwined links of life whose futures are now changing at a not-so-glacial rate.

Video: The History of Atmospheric Carbon Dioxide (October 2020).