Thought large lakes could not endure regime shifts? Our latest study by Rosalie Bruel used long-sediment cores to show that the luxuriant macrophytes forests described by Forel were lost just before the long-term monitoring program started. The lake we have monitored since then is an alternate stable state away from the one Forel was observing. The previous state was quite stable to 3°C changes in annual ambient atmospheric temperatures, the new state is, in contrary, quite sensitive. The legacy of past eutrophication is an hyper-sensibility to climate changes.