Antarctica conjures images of vast expanses of white ice and snow-covered mountains. But parts of the frozen continent are turning green and red. The sight may be striking, even beautiful, but the phenomenon has a less reassuring connection to climate change.
The coloured patches appearing on Antarctica’s white snow have attracted scientific attention. One contributing factor is penguin droppings, which supply nutrients to microscopic algae growing on the snow. Scientists suspect that this natural process may accelerate local melting, adding to the effects of a warming climate.
A study published earlier this month in the Journal of Geophysical Research: Biogeosciences suggests that nutrients from penguin droppings help snow-dwelling algae grow rapidly. As the algae spread, they change the snow’s colour and reduce its ability to reflect more sunlight and thereby melt faster.
Penguin droppings fertilise snow
Penguins feed on fish and other small marine animals. Nutrients from this food pass through their bodies and are deposited on land and snow in their droppings. By doing so, penguins inadvertently fertilise the algae that grow on the snow.
Snow algae do not always appear the same colour. When conditions are favourable and nutrients are plentiful, green pigments such as chlorophyll remain active. The algae use photosynthesis to produce food and grow rapidly.
When nutrients become scarce or conditions deteriorate, the algae may produce red pigments as a form of protection. These pigments help shield their cells from intense sunlight.
The researchers collected samples of snow covered with red and green algae from different locations across the western Antarctic Peninsula. They examined the abundance, colour and nutrient content of the algae, uncovering a link between nutrient deposits from wildlife and the growth of microscopic organisms on snow.
The researchers found significantly higher phosphate concentrations in snow samples containing green algae than in those containing red algae. Since phosphate supports algal growth and influence their colour, the findings suggest that nutrients from bird droppings may influence both the growth and colour of the algae.
Penguins are not the only birds involved. Seabirds such as skuas also deposit nutrients through their droppings, helping to transport nutrients from the sea to the land and snow.
Why the discovery matters
White snow reflects much of the sunlight that strikes it back into space. But when coloured algae spread across the surface, the snow becomes less reflective and absorbs more solar energy. This can accelerate local melting.
According to the study, snow covered with red algae can absorb about 20 per cent more solar energy than clean white snow. For snow covered with green algae, the figure rises to about 40 per cent.
This additional energy could accelerate melting in affected areas. But snow algae are not the sole cause of ice melt in Antarctica: rising temperatures and climate change remain major drivers. The researchers warn that failing to account for the effects of algae in models of snow and ice melt could lead to inaccurate estimates of how much ice-free land may emerge along Antarctica’s coast.
As the climate changes, some penguin populations may expand into new areas farther south, transporting nutrients and allowing algae to spread where they are not currently established. The extent of any such effects remains uncertain.
Antarctica’s changing colours illustrate how seemingly small elements of nature can have wider consequences. The interplay between penguin droppings, microscopic algae and sunlight offers scientists another way to understand the continent’s changing snow and ice.