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THE 4 SEASONS OF LEMAN

To what extent does the lake warm up or cool down during the year? How does its oxygen level change? And how does its transparency and the development of algae fluctuate? To better understand how it works, follow the evolution of the lake through the seasons.

Lake Geneva in spring

Warming and restart of algal growth

In the spring, the water quality measurement campaigns of the lake become fortnightly again to follow the warming of the water and the restart of the development of the algae in suspension in the water.

Winter mixing has led to the remobilisation of nutrients (mainly nitrogen and phosphorus) to the surface, which are necessary for algal growth. The spring warming, combined with the increase in solar radiation, allows the restart of algal growth in the nutrient-rich surface layer. The resumption of algal growth is accompanied by a decrease in the transparency of the surface waters.

Algae are important for the functioning of the lake as they form the basis of the food chain. Most of them are not a problem, but some species are problematic: those that clog fishing nets, and toxic cyanobacteria.

Limnological Bulletin - Spring 2022

(c) Maude Rion

(c) Maude Rion

The temperature of the waters of Lake Geneva in spring

Increased air temperature and longer daylight hours cause surface waters to warm up to a depth of about 30 m.

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Discover the latest data on temperature, Secchi transparency, turbidity and chlorophyll a concentration and their evolution.

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