ENVIRONMENT

As glaciers thaw, one colorful group of microorganisms is thriving. (The New Yorker)

Enough with the microbes—what else causes red snow?

Teachers, scroll down for a quick list of key resources in our Teachers Toolkit Text Set.

Discussion Ideas

• The terrific New Yorker article explains the phenomenon of “watermelon snow.” What is watermelon snow?
  • Watermelon snow, also called pink snow or blood snow, is snow inhabited by certain species of green algae. These single-celled organisms “are kin to seaweed, but instead of living in the sea they live in snow. (Snow weed, maybe?) They spend the winter deep in the snowpack, atop last summer’s snow, as dormant cysts. In the spring, they wake and swim up through the trickle of snowmelt to the surface, dividing and photosynthesizing as they go.”
    • Seaweed? Seaweed? Did someone say seaweed?

• Uh, if these microbes are green algae, why is there red snow?
  • As the snow algae get to the top of the snowpack, they turn red. The red coloring absorbs UV light. The algae need a certain amount of heat and liquid water to survive, and the increased radiation warms the organisms and melts the surrounding snow. (Pay attention to that.)

• The green algae in watermelon snow are the primary producers in the food web of their frozen ecosystem. (Did you even know glaciers could be an ecosystem?) What organisms are the primary consumers in the icy ecosystem?
  • In Iceland, consumers are tardigrades—those microscopic animals nicknamed “water bears.” Learn more about “hardy tardis” here.
  • In Chile, consumers are stoneflies.
  • In the Himalaya, consumers are midges.
  • In North America’s Pacific Northwest, consumers are little black ice worms. (Yes, those are a thing.)

• Why might watermelon snow be the “last snow on Earth”?
  • More algae, less snow.
    • Climate change is radically reducing the scope of the cryosphere, so snow cover is dwindling regardless of color. Get a “picture of practice” of what students think of melting ice and climate change here.
    • Watermelon snow is darker than white snow. Darker snow increases the amount of sunlight absorbed by the glacier or snowpack. This leads to a more rapid melting and more algae—a climate feedback loop. Learn more about how ice and snow cool the Earth with our great activity.
      • “‘Lo and behold, the more algae there were, the more melt there was,’ says the lead author of the new study. His team designed an algorithm for calculating melt, then used satellite imagery to generalize it across the entire field. “Seventeen percent of all the water that was melting was from snow that had algae on it. That’s a pretty big chunk.”

• So, lesson: Watch out where the huskies go … but should we be afraid of the red snow?
  • No. “It’s probably too early to get alarmed about snow algae … They are yet another indicator that humankind has barely begun to understand the resonances of its own existence, much less the steps it must take to insure its survival.” (And isn’t that a beautiful sentence about a sobering subject?)

TEACHERS TOOLKIT TEXT SET

The New Yorker: Why the Last Snow on Earth May Be Red

Nat Geo: Feedbacks of Ice and Clouds

Nat Geo: What is Blood Falls?