Researchers are beginning to investigate the species that cause alpine algal blooms to better understand their causes and effects.
Winter through spring, the French Alps are wrapped in verdant white snow. But as spring turns into summer, the steep slopes start to blush. Snowflakes take on bright colors: deep red, rusty orange, lemonade pink. Locals refer to it as “Sang De Glacier” or “Glacier Blood”. Visitors sometimes go with “Watermelon Ice”.
In reality, these blushes come from a shimmer of algae. In recent years, alpine habitats around the world have experienced an increase in snow algae blooms—dramatic, oddly set aggregates of these normally invisible creatures.
While snow algae blooms are poorly understood, that they are occurring is probably not a good sign. Researchers have begun surveying the algae of the Alps to better understand what species live there, how they survive and what may push them to the bleeding edge. Some of his preliminary findings were Published this week in Frontiers in Plant Science.
Small yet powerful, plant-like bacteria we call algae are “the basis of all ecosystems,” said study author Adeline Stewart, a doctoral student at the University of Grenoble Alpes in France. Thanks to their photosynthetic skills, algae produce big amount of the world’s oxygen, and form the foundation of most food webs.
But they sometimes overdo it, multiplying until they throw things out of balance. It can lead to toxic red tides, muddy freshwater blooms – or unstable glacier blood.
Although it’s not clear what exactly blooms, the color — often red, but sometimes green, brown or yellow — comes from pigments and other molecules that snow algae use to protect themselves from ultraviolet light. These colors absorb more sunlight, causing the underlying ice to melt more quickly. This could alter ecosystem dynamics and accelerate the shrinking of glaciers.
Inspired by increasing reports of the phenomenon, researchers from several alpine institutions decided to shift their attention from species of algae in far-flung habitats to “those growing next door”, said Eric Marechal, a professor at the University of Grenoble Alpes. Head of the Plant Physiology Lab and project leader.
Because many different types of algae can live and bloom in the mountains, the researchers began with a census in parts of the French Alps to find out what grows. They took soil samples from five peaks, which were spread at different altitudes, and discovered algae DNA.
They found that many species prefer particular altitudes, and are likely to thrive in the conditions found there. One dominant genus, named Sanguina, only grows above 6,500 feet.
Researchers brought some species back to the lab to investigate their potential bloom triggers. Algae bloom occurs naturally – the first written observation of glacier blood came from Aristotle, who guessed That the snow had grown the hairy red worm from lying down for too long.
But anthropogenic factors can make such eruptions worse and make them more frequent. Extreme weather, unseasonably warm temperatures and nutrient influx from agriculture and sewage runoff all play a role in freshwater and seaweed blooms.
To see if the same was true for glacier blood, the researchers subjected the algae to a surplus of nutrients such as nitrogen and phosphorus. While they haven’t found anything significant so far, they plan to continue this line of testing, Mrs Stewart said.
The limits of DNA sampling mean that even this study gives an incomplete picture of what is living in and under the ice, said Heather Maughan, a microbiologist and research scholar at the Ronin Institute in New Jersey, who were not involved in it. Still, it revealed the “incredible diversity” of alpine algae – underscoring how little we know about them, as well as their ability to “serve as beacons of ecosystem change.”
In the coming years, researchers will be tracking how species distributions change over time, which could shed light on the overall health of the ecosystem, Mrs Stewart said. They will also attempt to establish whether temperature patterns are related to blooms, and begin comparing species compositions in white versus colored snow. Eventually, they hope to decipher the blood-red message.
“There’s very little that we know,” she said. “We need to dig deeper.”