Until a little while ago, it was thought that Lake Tovel used to turn red was because of the presence of an alga, Glenodinium sanguineum.
The alga, which has a plasma that contains oily substances coloured by carotenoid pigments, was thought to cause the waters of the lake to turn red when it came to the surface in the summer months.
This phenomenon has not been seen since 1964, probably due to the reduced numbers of cows up in the summer pastures; it was in fact the cow’s droppings which provided the nutrients for the algae to feed on.
Recently, the Istituto Agrario di San Michele all’Adige discovered that the reddening of the waters of Lake Tovel was not caused by Glenodinium but by three species of algae: Tovellia Sanguinea (a “red” species today found in small quantities, given the lack of nutrients), Baldinia Anauniensis (a “green” species today found in vast quantities, giving the lake its current distinctive colour) and a third one whose identity is still the subject of research.
