From the shore to the mountain, a succession of plants take their place around the lake; these are the three belts of Lake Geneva. Imagine entering the lake step by step; first you will come across emergent plants (e.g. reed beds), then as you gradually enter the water you will find aquatic plants with floating leaves (e.g. water lilies) and finally submerged grass beds, those plants that tickle you when you swim in the lake. Unfortunately, due to eutrophication (accumulation of nutrients) but above all to artificial shorelines (riprap, concreting, etc.), the first two belts are rare, which considerably weakens the biodiversity of Lake Geneva. Restoring these two belts and halting any further deterioration of the coastal zone are crucial.
Submerged plants are therefore more common, but this does not mean that they are robust. The transparency and quality of the water play a major role in the health of these plants. They are doing much better now that phosphate levels in the water have fallen. Developing only during the warm seasons, these meadows spend the winter in the form of rhizomes, full of nutrient reserves, before growing again the following year. These lake meadows are therefore a seasonal source of life and habitat in Lake Geneva. From April to November, the meadows provide temporary shelter and food for aquatic fauna ranging from small invertebrates to fish. Several species of fish, such as tench and pike, use the beds as spawning grounds, where their fry can hide and feed. We are currently in the middle of the flowering period. To help you recognise the different species that are commonly seen, the ASL has created a booklet of identification cards, which you can order by clicking here. here.
The meadows of Lake Geneva have vital functions for the lake ecosystem, which fully justify the attention that must be paid to protecting them (limiting mowing and the anchoring of boats in the meadows).
Information from the lettre du Léman n°40, September 2010, CIPEL
Photo credit : Fondation des Grangettes
