Lake Cadagno is ideally suited for ecological studies and for investigations on metabolic responses of aquatic bacteria, especially of the phototrophs, to environmental signals such as light and environmental redox conditions. The dynamics of the water chemistry and the special conditions which follow from it, are consequences of geological features, the lithology in the catchment area and the morphology of the lake basin as well as the metabolism of the bacteria, mainly the phototrophs and the sulfate reducers.