The Pyrenees mountain lakes are turning green due to a phenomenon known as glacial flour. Glacial flour is a fine, rock sediment produced by the grinding action of glaciers. When glaciers melt, they release glacial flour into the water, which gives the lakes a milky, greenish appearance.

The amount of glacial flour in a lake depends on several factors, including the size and activity of the glaciers that feed it, the rate of melting, and the amount of rainfall. In the Pyrenees, the glaciers are relatively small and not very active, so the lakes do not receive a lot of glacial flour. However, the rainfall in the Pyrenees is high, which helps to wash the glacial flour into the lakes.

The green color of the lakes is also affected by the presence of algae and other microorganisms. These organisms can grow in the glacial flour, which provides them with nutrients and protection from the sun. The algae and microorganisms can also give the lakes a bluish-green color.

The green color of the Pyrenees mountain lakes is a beautiful and natural phenomenon. It is a reminder of the powerful forces that shape the Earth's surface, and it is also a sign of the delicate balance between the glaciers, the lakes, and the surrounding environment.