It is a surprising wonder of nature: pink lakes. Their color is due to the presence of microorganisms, also making them interesting for scientific research. One of these lakes, partially pink, is located in Ticino.
The planet Earth is a world rich in natural wonders, ranging from the most imposing mountains to the depths of the oceans, to the forests rich in biodiversity to breathtaking deserts. Some of them are undoubtedly linked to aquatic environments, habitats that we generally associate with blue color. This is why, when they appear in another form, they intrigue us and fascinate us.
There are, for example, lake circles that sometimes make the news in the press and are the subject of many scientific research because of their pink color, such as Lake Retba in Senegal or Lake Natron in Tanzania, to name a few.
These colors, ranging from deep to red, constitute a real natural spectacle. However, these environments are inhospitable for many forms of life because of their high salinity. Microorganisms tolerant of these particular conditions (called halophilic species) live there, giving water its characteristic pink color. These are sometimes bacteria, sometimes microscopic algae.
The salina sne
Among these, the microalgue “Dunaliella Salina” is one of the main causes of the phenomenon, but not the only one. To protect themselves from intense solar radiation, these algae produce large quantities of β-carotene, an orange-red pigment which gives water its reddish or pink tones. The higher the salt concentration of the lake, the more intense the color.
In shallow lakes or located in very hot areas, evaporation is rapid and constant, which increases salinity and creates ideal conditions for the growth of these pigmented microorganisms. It is no coincidence that many pink lakes are found in desert areas or subject to extreme climates.
A Ticino Rose Lake
But to see waters tinged with rose, even partially, it is not necessary to go to the other end of the world. There is also pink in the Ticino Alps, especially in Lake Cadagno, in Val Piora.
Lake Cadagno is “merotic”, which means that it is permanently laminated, with two layers of bunk water. This particular characteristic which makes this Lake Alpin of international interest has been studied by generations of researchers.
The upper layer of the lake, in contact with the atmosphere, can be considered as a classic alpine lake powered by cast iron waters. The water flows over granite rocks and is low in minerals, which makes it lighter than that of the lower layer. The deeper layer, meanwhile, receives neither water nor oxygen from the outside, but is powered by sublacustrous and underground sources, which bring the lake rich in minerals.
A pink bacterial strip
Sun light always enters the contact area between the two layers, but there is no oxygen, a situation that creates ideal conditions for the development of anaerobic photosynthetic bacteria (that is to say those that live in the absence of oxygen), visible as a pink bacterial strip separating the two layers of the lake.
A pink bacterial strip that helped make Lake Cadagno an important scientific destination, so much so that a TED video has looked into the subject, a first in Ticino: Ticino:
For 40 years, the lake has become a unique model for global research. In addition to an ecosystem of particular scientific interest, it houses a precious research station managed by the Alpine Biology Center (CBA). The presence of laboratories and accommodation establishments at 2000 meters above sea level, founded in 1994 in collaboration with the Canton of Ticino and the universities of Geneva and Zurich, played a key role in promoting this enchanting alpine corner, confirming its great scientific importance.
Article original: Christian Bernasconi (RSI)
French adaptation: Julien Furrer (RTS)