https://blog.rapusia.org/climate_crisis/41/purple-algae-on-italian-glaciers-confirm-global-warming/

Purple algae on Italian glaciers confirm global warming

JULY 10, 2020 10:00

by LORENZO CIOTTI   |  VIEW 223

The survival of Italian Alpine glaciers is threatened by global warming, lower annual snowfall but also by the presence of single-celled algae. The same responsible for the formation of the so-called dark zone of Greenland.

A large area of ​​the polar ice cap, which extends for about 100,000 square kilometers, characterized by an evident darkening of the ice surface. This phenomenon, albeit on a smaller scale, also occurs on alpine glaciers.

In a recent study conducted by researchers from the University of Milan Bicocca, molecular confirmation of the presence in alpine ice of the same alga responsible for the phenomenon was found of the purple ice in Greenland: the Ancylonema nordenskioeldii.

The results of the study, entitled Glacier algae foster ice-albedo feedback in the European Alps, were recently published in the scientific journal Scientific Reports. That glaciers host life forms, from microbes to arthropods and annelids is nothing new.

Peculiarity of the single-celled alga Ancylonema nordenskioeldii, as explained by Dr. Di Mauro in an interview with Bicocca News, is that unlike the other organisms, normally detectable in small cavities in the ice, called cryoconite holes, it is found dispersed on the surface of the glacier, where it can give rise to real "algal explosions" in the warmer seasons.

Just like in the case of Chlamydomonas nivalis, a green alga associated with the phenomenon of pink snow. The two algal species act on snow and ice according to the same mechanism. Following the spore germination in optimal summer conditions, the production of purple photosynthetic pigments activates the so-called bio-albedo feedback phenomenon.

The albedo of the glaciers decreases and further accelerates the melting of snow and ice. Favoring the presence of a thin layer of water that allows them to survive in conditions that would otherwise be hospitable for life, said the researchers.

Algae on glaciers

In order to identify the microorganism responsible for this phenomenon in the European Alps, the team took samples on the Morteratsch glacier and sequenced the DNA of the organisms present. At the same time, microscopic studies were carried out which highlighted the presence of colonies of Ancylonema nordenskioeldii.

Quantifying the impact of an alga on the stability of a glacier, according to the research coordinator, nowadays becomes an essential element for correctly developing predictive models that describe potential future scenarios.

“The scientific community is aligned on the fact that the melting of glaciers is a consequence of the ongoing climate change. An interesting study recently showed that 90 percent of Alpine glaciers could disappear by the end of the century due to these processes.

The presence of algae on the surface of the glaciers was not taken into account in that study. And alas, it could lead to further disheartening estimates for the future of alpine glaciers," says Biagio Di Mauro, of University Milan Bicocca.

At the end of the coronavirus emergency, the research team therefore has to carry out new analyzes on the Morteratsch, which allow to map the concentration of the alga on the ice starting from images acquired by drone and satellite, in order to evaluate the effect of the microorganism on the mass balance of the glacier.