A lake in Germany has turned deep purple in what has been described as a “science phenomenon”. Lake Allgäu in the Bavarian Alpine state in Germany turned dark purple on Wednesday (3 April), without any human intervention. As a result, the lake is now attracting visitors from all over the country and has been described as a “science and esthetic odd-looking phenomenon.” The German state environment office said purple sulfur bacteria is behind the change in water colour. The colour is now weaker and could disappear completely when it next rains.