Penguin droppings are accelerating coastal snowmelt along the Antarctic Peninsula by fertilizing green snow algae blooms that absorb substantially more sunlight than clean snow. Researchers warn that current climate projections omit this biological darkening effect, potentially underestimating how rapidly ice-free terrain will expand across the region.
Antarctica is widely pictured as a realm of pristine white ice. Yet along the rugged coastline of the Antarctic Peninsula, summer snowfields are taking on vivid hues of red and green. A new study published in the Journal of Geophysical Research: Biogeosciences reveals that this seasonal discoloration is driven in large part by an unlikely source: the relentless waste produced by nesting seabirds. Titled Phosphate Enrichment From Wildlife Inputs Shapes the Distribution and Pigmentation of Green and Red Snow Algae Along the West Antarctic Peninsula,
the paper was authored by Elise Ryan, with senior author Alia Khan, a cryosphere biogeochemist at the University of Colorado Boulder who began the work at Western Washington.
Phosphate Enrichment and Algal Pigmentation Along the West Antarctic Peninsula
The research team, which collected 111 snow samples along the West Antarctic Peninsula coastline between 2024 and 2025, found that microscopic snow algae change color depending on their nutritional environment. When nutrients run low, the single-celled organisms hunker down and produce sunscreen-like red pigments to shield themselves from intense polar radiation. Where nutrients are abundant, however, the algae shift strategy, packing their cells with chlorophyll to maximize photosynthesis during the frantic weeks of the Antarctic summer.
That nutrient abundance is delivered directly by local wildlife. Laboratory analysis of the collected snow revealed that patches dominated by green algae contained significantly higher concentrations of phosphate than red snow areas.
The penguin guano acts as a fertilizer… that fuels these dense green snow algae blooms.
Alia Khan, cryosphere biogeochemist and senior author of the study
Working in the field presented distinct practical hurdles for the scientific team. Traveling by boat across the rough seas of the Drake Passage, researchers spent long hours gathering samples across five degrees of latitude. Poop can visually look similar to the red snow algae
, Khan noted, adding that fieldwork near the colonies is very stinky
because the birds are just waddling around in their poop and tracking it all over the snow
.
Differential Sunlight Absorption Rates Between Green and Red Snow Algae
The color shift carries major physical consequences for the snowpack itself. Clean white snow reflects the vast majority of incoming solar radiation back into space. Algal pigments act similarly to a dark shirt on a summer afternoon, trapping solar energy and accelerating the melt rate.
| Snow Surface Type | Sunlight Absorption Increase | Primary Nutritional Driver |
|---|---|---|
| Red Snow Algae | Absorbs about 20 percent more energy than clean snow | Nutrient-starved conditions |
| Green Snow Algae | Absorbs about 40 percent more energy than clean snow | Phosphate enrichment from penguin guano |
Because green snow absorbs about 40% more sunlight energy than clean white snow—roughly doubling the 20% absorption increase documented in red snow—guano-driven fertilization creates a powerful local warming feedback loop. Meltwater further aids the spread of the microorganisms, linking the marine food web directly to terrestrial snow ecology.
Implications for Climate Models and Regional Melting Projections
The study highlights a blind spot in current environmental forecasting. Large-scale computer models projecting ice-free terrain expansion in Antarctica do not yet account for biological darkening effects caused by wildlife inputs.
“The link between wildlife, nutrients, and snow algae is a critical missing component in projections of expansion of ice-free areas in Antarctica,”
Alia Khan, assistant professor and a cryosphere biogeochemist at the University of Colorado Boulder
“Without accounting for these biological darkening effects, we are likely underestimating how rapidly coastal snowpacks are melting and how fast ice-free terrain will expand across Antarctica.”
Alia Khan, assistant professor and a cryosphere biogeochemist at the University of Colorado Boulder
Furthermore, changing climate conditions are actively altering penguin migration patterns, with colonies occasionally shifting southward. As the birds establish new breeding grounds, guano-fertilized algae habitats have the potential to follow, spreading their melt-enhancing effects over wider coastal areas.
While researchers acknowledge that seasonal snowpack melting differs fundamentally from the massive inland ice sheets driving global sea-level rise, the localized impact on coastal ecosystems is direct. The research team emphasizes that gathering additional field data remains necessary before biological darkening variables can be formally integrated into standard melt models for the Antarctic Peninsula.