On planet Earth, plants play a very important role in ensuring balance through a well-known phenomenon: 𝐥𝐚 𝐩𝐡𝐨𝐭𝐨𝐬𝐲𝐧𝐭𝐡𝐞̀𝐬𝐞. This is the process by which plants transform carbon dioxide, present in the air, into oxygen, through the action of 𝐥𝐮𝐦𝐢𝐞̀𝐫𝐞 𝐬𝐨𝐥𝐚𝐢𝐫𝐞. This process not only allows them to grow, but also ensures oxygen availability for 𝐭𝐨𝐮𝐭𝐞𝐬 𝐥𝐞𝐬 𝐞𝐬𝐩𝐞̀𝐜𝐞𝐬 𝐯𝐢𝐯𝐚𝐧𝐭𝐞𝐬 𝐬𝐮𝐫 𝐥𝐚 𝐩𝐥𝐚𝐧𝐞̀𝐭𝐞.
The same thing happens in the lake. Like all species on earth, those living underwater also need to breathe! That's where aquatic plants come in. One of their roles is to provide 𝐭𝐚𝐮𝐱 𝐜𝐨𝐧𝐬𝐭𝐚𝐧𝐭 𝐝'𝐨𝐱𝐲𝐠𝐞̀𝐧𝐞 𝐝𝐢𝐬𝐬𝐨𝐮𝐭 𝐝𝐚𝐧𝐬 𝐥'𝐞𝐚𝐮 through photosynthesis. In fact, the underwater world of Lake Geneva is home to a multitude of macrophyte varieties that give rise to veritable sub-lacustrine forests. They can be found at 𝐣𝐮𝐬𝐪𝐮'𝐚̀ 𝐮𝐧𝐞 𝐩𝐫𝐨𝐟𝐨𝐧𝐝𝐞𝐮𝐫 𝐝𝐞 𝟏𝟎 𝐦𝐞̀𝐭𝐫𝐞𝐬 or thereabouts, where light can still penetrate. Characeae, myriophylls and periwinkle pondweeds dance with the currents to paint a magnificent picture of shades of green, blending into the blue hues of Lake Geneva.
In addition to their role as "𝐩𝐨𝐮𝐦𝐨𝐧 𝐥𝐚𝐜𝐮𝐬𝐭𝐫𝐞", these forests provide support for 𝐟𝐫𝐚𝐢𝐞𝐬 𝐩𝐨𝐮𝐫 𝐥𝐞𝐬 𝐩𝐨𝐢𝐬𝐬𝐨𝐧𝐬, 𝐞𝐭 𝐬𝐞𝐫𝐯𝐞𝐧𝐭 𝐝𝐞 𝐧𝐨𝐮𝐫𝐫𝐢𝐭𝐮𝐫𝐞 𝐨𝐮 𝐝'𝐡𝐚𝐛𝐢𝐭𝐚𝐭𝐬 𝐝𝐞 𝐧𝐨𝐦𝐛𝐫𝐞𝐮𝐱 (Perch, Pike, Roach....), 𝐢𝐧𝐯𝐞𝐫𝐭𝐞́𝐛𝐫𝐞́𝐬 (molluscs, crustaceans, insect larvae...) 𝐞𝐭 𝐨𝐢𝐬𝐞𝐚𝐮𝐱 𝐝'𝐞𝐚𝐮 (Coot, Ruddy Gull...). Since the 1980s, the concentration of phosphorus in the lake has fallen significantly, so aquatic plants have adapted to their environment.
In view of the 𝐚𝐦𝐞́𝐥𝐢𝐨𝐫𝐚𝐭𝐢𝐨𝐧 𝐝𝐞 𝐥𝐚 𝐪𝐮𝐚𝐥𝐢𝐭𝐞́ 𝐝𝐞 𝐥 𝐞𝐚𝐮 and the resulting transparency, plants can thus colonise more ground at depth. This is why the presence of these aquatic plants serves as 𝐢𝐧𝐝𝐢𝐜𝐚𝐭𝐞𝐮𝐫 𝐪𝐮𝐚𝐧𝐭 𝐚̀ 𝐥𝐚 𝐬𝐚𝐧𝐭𝐞́ 𝐝𝐮 𝐋𝐞́𝐦𝐚𝐧. Although they do not always delight bathers and boat owners, these sublacustrine forests are 𝐩𝐫𝐢𝐦𝐨𝐫𝐝𝐢𝐚𝐥𝐞𝐬 𝐩𝐨𝐮𝐫 𝐥𝐚 𝐛𝐢𝐨𝐝𝐢𝐯𝐞𝐫𝐬𝐢𝐭𝐞́.
We invite you to take a closer look at them with our 𝐟𝐢𝐜𝐡𝐞𝐬 𝐝𝐞 𝐝𝐞́𝐭𝐞𝐫𝐦𝐢𝐧𝐚𝐭𝐢𝐨𝐧𝐬 available on in our 𝐛𝐨𝐮𝐭𝐢𝐪𝐮𝐞 𝐞𝐧 𝐥𝐢𝐠𝐧𝐞.
𝐒𝐨𝐮𝐫𝐜𝐞𝐬 :
ASL" leaflet A sub-lake forest "
Tribune de Genève, 16 August 2020 " The quality of Lake Geneva's water is improving, as its plants tell us "
