where do these high mountain red snows come from?

Nicknamed “the blood of the glaciers”, the micro-algae that inhabit the high altitudes and color the snow in shades of ocher and red are said to be markers of climate change.

Every year since 2017, Éric Maréchal, research director at the CNRS and director of the cell and plant physiology laboratory, has visited the Jardin du Lautaret. In this research center perched at 2100 m between the Col de Cerces and the Parc des Ecrins, he studies a microscopic algae which has the particularity of coloring the snow red.

At the head of a consortium called Alpalga, made up of researchers from CNRS, INRAE, Météo-France and Université Grenobles Alpes, Éric Maréchal offers a systemic approach to mountains, explaining how each micro-ecosystem will influence another. The team’s first research report is released June 7. Éric Maréchal detailed their observations to Numerama.

Where do these red colored snows come from?

This is the big question we ask ourselves. Every year we see red snows developing in the névés – those late spring accumulations of snow that settle and keep in the cooler places. It is towards the end of June-beginning of July, that we sometimes observe an algae proliferation that will color the snow.

The latter constitutes in a very specific environment, like seawater. When you take seawater in your hands, you know that even if you can’t see anything, the water is full of micro-algae and phytoplankton. Snow is like an ocean, but a transitory ocean, that appears and disappears, and this micro-ecosystem evolves with it. The algae that are part of it can only grow in snow, and when it is not there, in another stage of their life, they surely remain dormant in the ground.

How is this algae micro-ecosystem organized?

These algae are unicellular beings, which feed on the CO² in the atmosphere. They are primary producers, the point of entry into life: all the living carbon that constitutes us and that we feed on comes from primary producers.

They can evolve and move in the air, like pollen. We might think they’re all the same. But we analyzed the soil between 1000m and 3000m altitude, every 200m, and found that there were different types of algae depending on the altitude. Some algae are cosmopolitan, while others are only present at low or high altitudes. Their distribution is influenced by very specific conditions which change rapidly in the mountains. Hikers know it: as soon as you climb 200 m, there is less oxygen, and more light. It also changes the composition of soils.

© Jean-Gabriel Valay / Lautaret garden / UGA / CNRS

You focused on Chlorophyta algae in your study. Why ?

The Chlorophyta, Green Algae in botany, are one of the most diverse and important groups in the biosphere, which has conquered the entire land and air environment. But it is also one of the least well studied, while its diversity is impressive. When you look at this group, you realize that there are thousands of different species, and in evolutionary terms, we are less distant from the platypus than two species of Chlorophyta.

Why do these green algae turn red?

Like us, when we are in the sun, they burn, even if they are in 0 ° snow. To protect themselves, they apply their own sunscreen, a red carotenoid (as in carrot) molecule.

How does global warming affect this micro-ecosystem?

The CO² in the atmosphere is thought to have an effect on photosynthetic organisms. We do not know exactly what causes the proliferation of snow algae, but we have indications that this phenomenon is increasing year after year, with the warming of the atmosphere. One thinks that algae are markers of global warming.

But they are also actors: as they start to swarm, they color the snow red, and as you have experienced, a white garment will reflect heat, while a red garment will retain it. The snow will therefore heat up, which will accelerate the phenomenon of melting ice.

Is it possible to curb this phenomenon?

We are not here to modify nature, but to understand it and support the effects of climate change. Humanity has so far failed to find a solution to this phenomenon which affects the entire environment. There can only be a global effort to decrease human action and lower the temperature, because local and surgical actions are useless. We have tried actions to preserve the environment, but have never succeeded in preserving anything.

You have to understand what is happening: the world before will disappear, the world after will appear. We do not yet know the resilience of ecosystems, and do not know if the species we keep in the laboratory will be the last. It’s sad to see a world dying out, but you have to trust life, and see how ecosystems will survive and adapt to change. Our goal is to understand the dynamics of this change, and to offer an understanding and anticipation of what will happen in the mountains.

The continuation in video

Source: Numerama by www.numerama.com.

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