A few days ago, the small pond in a chalk quarry near Füssen in the Bavarian Alps suddenly turned a deep purple.
The coloring is not due to some spill of human origin but to the action of some bacteria which, in particular conditions of light and sulfur concentration, make their way to the surface of the water.
These bacteria are normally found in deeper, oxygen-free layers of water, where they find conditions favorable to their proliferation, the local environmental office said.
The phenomenon immediately attracted a large crowd of visitors, for most of whom, however, is not so much about science as seeing and photographing something unusual: “Bacteria! I thought they had spilled paint in them,” he said someone.
An unusual but not unique spectacle on the Allgäu lake, the action of the purple bacteria, has already occurred once in 2020 and another time in 2021.