Snow algae: pretty peril of the slopes

In many alpine areas of the world, melting snow and glaciers supply water during the warmer months. An estimated one-sixth of the world’s population depends on these streams.

But sometimes, colorful “snow algae” bloom, allowing pigments in their cells to soak up sunlight that the snow and ice would otherwise reflect. This input of energy causes extra melting that, if unchecked, would hasten the disappearance of these vital water sources as the world warms.

In Associate Professor Trinity Hamilton’s University of Minnesota lab, several researchers are tackling this problem. 

First, the team checks the internet for reports of snow algae in alpine regions of the United States. Next, they travel to those regions, which include places in the Rockies and the Cascades. On site, they gather data on these unusual microorganisms in order to figure out their potential roles in our planet’s environmental future. 

“There was one study in Alaska where they actually linked 11 percent of loss of glacier ice and snow to the impact of darkening from snow algae,” says Jeff Havig, a geochemist and a contributor in Hamilton’s research project within the College of Biological Sciences. 

Earth’s alpine and polar regions are particularly susceptible to rising temperatures, so “it's really important to understand the role they are playing in generating melt and other dynamics we don't understand,” Hamilton says.

What’s feeding the algae?

This National Science Foundation-funded work seeks to identify nutrients—and their sources—that sustain the snow algae. Nitrogen-containing compounds are a major suspect, since these are produced by burning and can be deposited far from their point of origin by wind-borne rain or dust. 

After arriving in a “blooming” alpine area, postdoctoral researcher Pablo Almela filters biomass to perform analyses of the algal DNA, carbon and nitrogen isotopes, and other potentially telltale chemicals.

“And then there's water that's collected for water chemistry,” says Havig. “It’s a big process.”

In one surprising result, the researchers found that a rise in environmental phosphorus—not nitrogen—may play a bigger role in promoting snow algae growth than scientists had thought.

The team also discovered that snow algae can reduce the reflection of sunlight and cause faster melting even when they grow below the surface of the snow. 

“We know the impact of the algae when it’s growing on the surface, but we know almost nothing about the blooms happening underneath,” Almela explains.

Shrinking that information void is definitely on Almela’s—and his colleagues’—to-do lists. 

This is based on a story from the College of Biological Sciences. Read more and see more terrific images.