Bloody tears of glaciers: why the snow in the mountains turns red

Scientists at the Laboratory of Cell and Plant Physiology in Grenoble, France, are studying a phenomenon known as "glacial blood" in the Alps, LiveSience reports. In reality, these eerie spots for an uninitiated person are nothing more than microalgae that live in the snow at an altitude of 1000 to 3000 meters above sea level. Not everyone knows that, as in the oceans, algae live in the soil and snow on the tops of mountains, the cells of which are only a few thousandths of a millimeter across. Through photosynthesis, microalgae produce sugar, and the entire ecosystem feeds on this, regardless of whether it is in the ocean or in the compacted snow in the mountains.

Formally, the algae that color the snow red are classified as green algae, since they belong to the Chlorophyta type and contain a specific form of chlorophyll, a green pigment that enables photosynthesis. But besides chlorophyll, these algae also contain carotenoids - orange and red pigments found in vegetables like carrots. Carotenoids act as antioxidants and likely protect algae from the damaging effects of intense light and ultraviolet radiation at high altitudes. During algal blooms, the surrounding snow may appear red or orange due to the build-up of carotenoids - hence the glacial blood pattern.

So far, scientists know little about the biology of algae and how they are affected by climate change. However, it can be assumed that just as nutrient-rich pollution fuels algal blooms in the ocean, nutrients carried into the mountains by rain and wind may fuel algal blooms at the top. An increase in the level of carbon dioxide in the atmosphere can also stimulate their growth. The question is whether these changes will cause a snowball effect in the surrounding ecosystem. This is possible if only because reddish snow reflects light less efficiently than pure white, and melts faster. If, due to climate change, the red snow of microalgae appears more often, it can harm neighboring organisms.

Researchers examined the prevalence of different types of microalgae in five different locations in the French Alps. They also took soil samples and studied the genetic material left over from dead algae cells that lived there before. This study, published in the journal Frontiers in Plant Science, serves as the starting point for the AlpAlga project, which is trying to tackle glacial blood questions: what environmental conditions cause algal blooms; how the seasonal appearance and disappearance of snow affects the life cycle of algae; how bloom affects snow melt and glacier retreat.

The melting of glaciers in the polar regions often makes headlines: their impact on sea level rise is obvious. However, climate change is also having a huge impact on landlocked glaciers in mountainous regions, where glacial water serves as a reservoir for river systems. Therefore, in the long term, the effects of climate change will be felt even in those mountainous areas that are far from the seashore.