Antarctic algal blooms: “Green snow” mapped from space (Study).
More of Antarctica is set to be covered in “green snow” as global temperatures increase, researchers have said.
A team led by Matt Davey, from the Department of Plant Sciences at the University of Cambridge, U.K., used satellite data and ground observations to create a large-scale map of algal blooms that appear along the Antarctic Peninsula during the continent’s summer.
Snow algae were first described during expeditions to Antarctica in the 1950s and 1960s. Since then, it has been studied at several locations, with researchers finding a range of algal species.
The blooms form on the top of snow in warmer areas along the coast, where temperatures tend to stay above 0 C. It normally appears between November and February, with growth accelerated by the presence of nitrogen and phosphorus.
In a study published in Nature Communications, researchers mapped the algae to understand how it may be affected by warmer global temperatures predicted for the coming decades. Because algal blooms act as a carbon sink, removing carbon dioxide from the atmosphere via photosynthesis, understanding its response to climate change is important.
“We identified 1,679 separate blooms of green algae on the snow surface, which together covered an area of 1.9 km2 [0.7 square miles], equating to a carbon sink of around 479 tonnes per year,” Davey said in a statement.
They found most of the blooms were on small, low-lying islands that are expected to lose their summer snow under warmer global temperatures. Without snow, the algae will not be able to form. They predict 62 percent of the blooms in these areas will be lost.
However, researchers found the algae will likely appear in larger blooms further north, with expansion over a larger landmass close to bird colonies.
“This increase is predicted to outweigh biomass lost from small islands, resulting in a net increase in snow algae extent and biomass as the Peninsula warms,” they wrote.
The team found most blooms were within around three miles of penguin colonies, and that the algal blooms were strongly influenced by marine birds and mammals. Feces from these animals, the team say, act as a fertilizer to help speed up algal growth.
“This is a significant advance in our understanding of land-based life on Antarctica, and how it might change in the coming years as the climate warms,” Davey said.
However, the researchers also say many uncertainties remain. “With multiple and often unknown species recorded within patches of green snow algae, and little known about the dispersal mechanisms, life cycles and plasticity of snow algal species, losses from these islands could represent a reduction of terrestrial diversity for the Antarctic Peninsula,” they wrote.