Penguin guano (poop) fertilizes green snow algae along the Antarctic Peninsula, causing denser green blooms that absorb more sunlight and accelerate snowmelt compared to clean white snow.

A study published in the Journal of Geophysical Research: Biogeosciences (led by researchers including Alia Khan of the University of Colorado Boulder) analyzed 111 snow samples from coastal sites.

Snow algae can appear red or green depending on conditions. When nutrients (especially phosphate from penguin and seabird guano) are scarce, algae produce red protective pigments and go relatively inactive.

With abundant phosphate, supplied when penguins feed at sea on marine organisms and then track or deposit their nutrient- rich droppings on the snow, the algae pack cells with green chlorophyll pigments, become denser, and photosynthesize more actively.

These colored patches darken the snow surface:

• Red snow absorbs roughly 20% more solar energy than clean white snow.
• Green snow absorbs about 40% more (roughly twice the extra energy absorption of red snow in some descriptions), heating the snow and speeding melt.

As Antarctic temperatures rise, snow algae habitats are expanding along coasts. Penguins and seabirds (such as skuas) link the marine food web to snow ecology by spreading these nutrients, intensifying the green blooms near colonies.

Researchers note that without accounting for this biological darkening, models likely underestimate how quickly coastal snowpacks melt and ice- free terrain expands. Fieldwork near colonies was notably smelly, as penguins track guano widely across the snow.

This is a newly highlighted feedback in Antarctic coastal systems rather than a primary driver of continent-wide ice loss.

Penguin guano (excrement) is a major ecological driver in Antarctic and sub- Antarctic ecosystems.

It acts as a powerful natural fertilizer that transfers marine- derived nutrients to land, influencing soil formation, biodiversity, atmospheric chemistry, and even local climate feedback. Impacts range from highly localized (around colonies) to regional, with both positive and complex climate- related effects.

1. Nutrient fertilization and soil enrichment

Penguins feed primarily on krill, fish, and other marine organisms, concentrating nitrogen (N), phosphorus (P), organic carbon, and trace metals (e.g., iron, copper, zinc) in their guano. Colonies deposit enormous quantities, seabirds (including penguins) globally contribute hundreds of gigagrams of N and P annually, with Antarctic and Southern Ocean coasts receiving some of the highest inputs per unit area.⁠

• Soil formation (ornithogenic soils and phosphatization): Guano drives chemical weathering and creates specialized phosphate- rich soils. It forms minerals such as struvite and hydroxyapatite, elevating organic P, N, and organic matter. Abandoned colonies leave lasting “ornithogenic” soil legacies that influence landscape evolution after glacial retreat.⁠
• Nitrogen and phosphorus cycling: Guano inputs can exceed agricultural fertilizer rates by orders of magnitude locally (e.g., tens of thousands of kg N ha⁻¹ y⁻¹ in dense colonies). Ammonia volatilizes and spreads inland via wind, enriching soils kilometers away (up to ~240 times the colony area in some estimates). This boosts microbial activity and phosphine (PH₃) production.

2. Impacts on terrestrial biodiversity

Nutrient enrichment dramatically increases primary productivity and supports higher trophic levels in otherwise nutrient- poor Antarctic terrestrial environments:

• Mosses, lichens, algae, and microbial communities thrive near colonies.
• Invertebrates (e.g., springtails) can be ~10 times more abundant in influenced moss communities than in milder European grasslands.
• Overall biodiversity and biomass are elevated in the “halo” around active and abandoned colonies.

3. Effects on snow and ice (recent discovery)

A 2026 study (Journal of Geophysical Research: Biogeosciences) showed that phosphate from penguin (and other seabird) guano fertilizes coastal snow algae along the Antarctic Peninsula.

• Nutrient- rich conditions keep algae in a dense, green (chlorophyll- rich) state rather than a red, dormant “sunscreen” state.
• Green snow absorbs ~40% more solar energy than clean white snow (vs. ~20% for red snow), accelerating local snowmelt and potentially expanding ice-free areas as temperatures rise and penguin ranges shift.

This links the marine food web directly to snow- surface ecology and is previously under- accounted biological feedback in melt projections.

4. Atmospheric and climate effects

Guano releases large amounts of ammonia (NH₃). Near Adélie penguin colonies, atmospheric ammonia can reach 1,000 times background levels (and remain elevated for weeks after birds leave).

• Ammonia reacts with sulfuric compounds from marine phytoplankton, boosting formation of aerosol particles (cloud condensation nuclei) by up to 1,000- 10,000 times.
• This enhances low- level cloud and fog formation, which can reflect sunlight and exert a local cooling effect, potentially partially offsetting regional warming. However, the net climate impact depends on cloud location (over ice vs. ocean) and remains an active research area. Declining penguin populations could reduce this cooling feedback.

5. Marine and coastal connections

• Guano and runoff return nutrients (including iron) to nearshore waters, stimulating phytoplankton growth and supporting the base of the marine food web.
• Trace metals recycled via guano contribute to Southern Ocean productivity.
• Historical human harvesting of guano (especially in South America) has disrupted nesting habitats for some penguin species (e.g., Humboldt penguins that burrow in guano deposits).

Broader context and vulnerabilities

Penguin colonies function as biological “pumps” moving nutrients from ocean to land and atmosphere.

Their ecological role is outsized relative to their biomass. However, many penguin populations face pressures from sea- ice loss, shifting prey availability (krill vs. fish), commercial fishing, and disease.

Declines could weaken these nutrient- transfer and climate- modulating services, creating potential positive feedback for local warming or reduced terrestrial productivity.

In summary, penguin guano is far more than waste, it is a keystone process shaping Antarctic biogeochemistry, biodiversity, snowmelt dynamics, and even atmospheric processes.

Research continues to quantify these interconnected effects amid rapid environmental change.

Phosphate Enrichment From Wildlife Inputs Shapes the Distribution and Pigmentation of Green and Red Snow Algae Along the West Antarctic Peninsula

This is the peer- reviewed paper corresponding to the recent news: “Phosphate Enrichment From Wildlife Inputs Shapes the Distribution and Pigmentation of Green and Red Snow Algae Along the West Antarctic Peninsula” by Elise Ryan and Alia Khan, published 7 October 2026 in Journal of Geophysical Research: Biogeosciences. 

The full text is available at the link you provided (via AGU/Wiley). Official press materials from AGU and EurekAlert summarize the key findings as follows:

Main findings

• Researchers collected 111 snow samples (red and green algal blooms) along the West Antarctic Peninsula coast, spanning sites with and without penguin colonies across about five degrees of latitude.
• Snow algae switch pigmentation based on nutrient availability:
  • Nutrient- scarce conditions → algae produce red (sunscreen- like) pigments and reduce growth. Red snow absorbs ~20% more solar energy than clean white snow, increasing melt.
  • Nutrient- rich conditions → algae pack cells with green chlorophyll pigments, stay active, and form denser blooms. Green snow absorbs ~40% more energy than clean white snow (roughly double the extra absorption of red snow), further accelerating melt.
• Green algal samples contained substantially higher phosphate levels (a key nutrient abundant in penguin and seabird guano) than red samples. Lab work involved counting algal cells under a microscope and extracting pigments and nutrients.
• Penguins (and other seabirds like skuas) act as a nutrient vector: they feed on marine organisms, then deposit and track phosphate- rich guano across coastal snow, fertilizing dense green blooms. This directly links the marine food web to snow- surface ecology.

Broader implications

As Antarctic coastal temperatures rise, snow- algae habitats are expanding. Penguin range shifts southward could further spread guano- fertilized green blooms, enhancing local snowmelt and the expansion of snow- and ice -free terrain. Current models of Antarctic melting do not yet include this biological “darkening” feedback; the authors note it is a critical missing component and that more data are needed before it can be fully incorporated into projections.

The work was supported in part by an NSF CAREER award to Alia Khan. Field sampling near colonies was described as particularly unpleasant due to the odor and visual similarity between guano and red algae.

Published: Journal of Geophysical Research: Biogeosciences 

DOI: 10.1029/2026JG009918

Provided: American Geophysical Union

Authors: Elise L. Ryan, Alia L. Khan

Abstract

Snow algae darken snow through biomass accumulation and pigmentation, yet nutrient controls on algal abundance and pigment composition in Antarctic snowfields remain poorly constrained. Along the West Antarctic Peninsula (WAP), coastal snowfields receive nutrient inputs from marine and wildlife sources that may influence bloom development. We analyzed 111 snow samples collected from nine coastal WAP sites during the 2024–2025 austral summer to assess the relationships between dissolved nutrients and algal cell density, pigment concentration, and pigment composition across red, green, and clean snow. In green snow, median phosphate (PO₄³⁻) concentrations were tenfold higher (114 μM) relative to red snow (11.4 μM), and ∼70-fold higher than clean snow (1.54 μM). High-phosphate samples, composed primarily of green snow, exhibited higher cell densities and per-cell pigment concentrations than low-phosphate samples, consistent with enhanced biomass and cellular pigment accumulation under phosphate-rich conditions. These results identify green snow as a bloom state strongly associated with elevated phosphate availability. Green snow was also characterized by lower NO−x :PO43−$$ ratios (NO₃⁻ + NO₂⁻: PO₄³⁻) and increased photoprotective carotenoids relative to red snow, suggesting that dense green blooms rapidly drawdown bioavailable nitrogen relative to excess phosphate, creating a distinct post-uptake stoichiometric signature in wildlife-influenced regimes. Phosphate concentrations were positively associated with wildlife influence (Spearman’s r = 0.54, p < 0.001), indicating ornithogenic inputs as a key phosphorus source. Collectively, these results link phosphate availability to snow algal biomass and cellular pigment composition and suggest that wildlife-mediated nutrient inputs may intensify algal-driven surface darkening.