

Image: Guoxiang Liu

It's easy to see how the "Red Stone Valley," in China's Mount Gongga got its name. Those colorful rocks look like they're painted, but the red actually comes from a newly discovered variety of a species of algae:

Related algae have long lived here, but only in 2005 did this vast red algal mat appear, becoming a spectacular local tourist attraction. Now Guoxiang Liu of the Chinese Academy of Sciences in Wuhan, Hubei, China, and colleagues have discovered that this was the result of a newly discovered variety of the algae Trentepohlia jolithus that suddenly expanded.

Why did it happen? Uniquely, this variety only grows on local rocks. In recent years, large debris flows combined with human activity, such as road construction, have exposed vast swathes of fresh native rock, ripe for the algae to colonise - and the mat has remained.

The mat's shocking red colour is related to organic pigments in the algae called carotenoids. These offer protection from UV radiation, allowing the algae to live in high altitude regions