The green snow of Antarctica
The coasts of the Antarctic continent are coloured in green due to climate change.
Thinking of Antarctica evokes white images of snow and ice, going on as far as the eye can see. But things could change, indeed they are already changing. Terrestrial life, although it seems impossible, exists even in those uncomfortable territories, especially along the coasts, and it is responding very quickly to the change of climatic conditions. Mosses and lichens are the two most important groups of photosynthetic organisms that are present in those areas and also the most studied, but apparently they are not the only ones. A recent study ("Remote sensing reveals Antarctic green snow algae as important terrestrial carbon sink") published in Nature Communications by a group of researchers from the University of Cambridge, described the importance in the Antarctic ecosystem of microscopic algae that "bloom" on the snow in coastal areas. They make a fundamental contribution to the carbon cycle and it seems that they will spread more and more with the increase of global temperatures.
The photosynthesis of algae
These microscopic algae with infinitesimal size, when they grow in mass, they give the snow a wonderful bright green color that is also visible from space. Their role is important as they perform, like plants and many other algae, the photosynthesis: they use sunlight to store carbon dioxide and release oxygen. Algae normally live in water where they proliferate when they find masses of nitrogen and phosphorus. There are various types of algae, from unicellular ones, such as those researched in study, to giant ones such as kelp.
Seaweed in Antarctica
The blooming of the algae in question, however, happens mostly along the Antarctic coast and on the islands off the west coast of the Antarctic Peninsula. They therefore grow in the "hottest" areas of the continent, where the average temperature, during the southern summer, is above zero. These are really the areas that are undergoing a sudden warming the most.
Another factor that seems to influence the presence of these algae, according to the results presented by the British team, is the proximity of sea birds and mammals, whose excrements act as fertilizer for these organisms. In 60% of cases, blooms happen within a radius of 5 km from a colony of penguins, or close to bird nesting sites, or in areas where seals arrive on the shore.
The study, using satellite images, identified, between 2017 and 2019, blooming areas of 1.9 km2 which represent a stockage of 479 tons of carbon per year. This is the amount of carbon dioxide emitted by 875,000 average journeys with a petrol car in the United Kingdom.
Climate change and the blooming of green algae
With the increasing of the temperatures, the green blooms of the algae could change areas: on the coasts, the perennial snow tends to melt and so these colonies of green microorganisms tend to disappear. But they seem to appear now in higher numbers in other higher and colder areas.
It seems that, ultimately, the area of Antarctica covered by "green snow" will increase with the increase of global temperatures and so the ability to store carbon dioxide on the continent. So will we have to get used to the idea of a green South Pole?