Microbiology: The glacial gardens that darken Earth

Ice caps host an extensive glacial garden of microbes, which can drastically reduce surface reflectivity and cut the amount of sunlight reflected back into space.

Researchers at Leeds University have undertaken what they say is the first ecological study addressing the entire microbial community of a glacial surface and its effect on reflectivity. The results, published in the journal FEMS Microbiology Ecology, should improve climate change models which have neglected the role of microbes in darkening Earth’s surface.

The scientists’ field trip to Mittivakkat glacier in southeast Greenland revealed a “microbial garden” of life forms on the ice, including “snow algae”, bacteria and fungi. “Skiers may have seen snow algae,” says Stefanie Lutz, lead author. “They are frequently referred to as ‘watermelon snow’.”

The reflectivity or albedo of the glacier was reduced by as much as 80 per cent in places where the coloured microbial populations were most dense. “Previously, it was assumed that low albedo, most often measured from satellites, was primarily due to soot or dust,” says Liane Benning, co-author. “However, our research provides a first ground-based measure for the microbial contribution to albedo.”

The results show that microbial communities strongly affect the reflectivity of glaciers and ice caps – and their impact may rise with more surface melting, creating conditions conducive to algal growth.