"Glacier blood" or "watermelon snow" is sweeping across the Alps and researchers are eager to figure out what's responsible for the mysterious phenomenon. A new study has found the culprit -- algal blooms. Now blooming en masse on mountains worldwide is the same kind of algae responsible for the dreaded red tide. Experts hypothesize that much like the ocean and freshwater algal blooms, these may also be caused by rapidly warming temperatures and human-made pollution.

Why This Matters

Algae is crucial to all life, producing about half of the world's oxygen. But when algae blooms rapidly, it can poison drinking supplies and kill wildlife. Just as people depend on lakes and rivers for their freshwater, researchers estimate that almost a quarter of the world’s lowland population, 1.5 billion people, will rely on mountain watersheds and snowmelt for their drinking water within the next 30 years. That water is now threatened by increasing algal blooms, in addition to existing threats from temperature rise and glacial bursts. But scientists say that they’re behind the curve on solving this problem.

Don't Eat the Red Snow

"There's so little that we know; we need to dig deeper," said Adeline Stewart, an author of the study and a doctoral student at Grenoble Alpes University in France. Colorful blooms occur all around the world, including in the Rocky Mountains, Greenland, and Antarctica. Researchers took soil samples from five mountain peaks and found that different species of algae bloom at different altitudes. These species span the color spectrum, some even turning the snow purple. Red algae, known as sanguina, bloomed only at altitudes above 2,000 meters. Green algae, on the other hand, bloomed only below 1,500 meters.

They then evaluated the samples to see what kind of activity triggered a bloom.

• Although algal blooms often occur naturally, they are often exacerbated by surpluses of nutrients like nitrogen and phosphorus.
• Researchers also hypothesized that increased snowmelt and shortening winters could disrupt the life cycle of algae, causing an increase in blooms.

Temperatures in the European Alps have been rising much faster than the global average and have increased by 3.6 degrees Fahrenheit above pre-industrial temperatures. The world’s mountains could lose half of their glaciers by 2050.

Scientists are determined to understand the direct cause of these increasing snowy blooms. This month, AlpAlga, the French team investigating the "glacier blood," will embark on an expedition into the Alps to evaluate how algal blooms vary season to season. But as mountains warm and glaciers melt, time is of the essence to find ecological balance on the world's highest peaks.