sulphur purple bacteria colour a lake in allgaeu red, pink or purple

accident alatsee algae allgaeu bacteria bacteriochlorophylls bad bavaria bleeding blood carotenoids chemical chromatiaceae color colorful coloring colour conspicuous ectothiorhodospiraceae extraordinary faulenbach feet forest germany gypsum hydrogen lake landscape natural nature non outdoors outside phenomenon pink poison poisonous pond proteobacteria purple rare red rust spectacle spring sulfide sulfur sulphur toxic water