In order to assess the impact of extremes on the seasonal cyanobacteria biomas sand its diversity, the average of the sampling months corresponding to the same seasons was calculated, within the lakes and affiliated to the same ET-Class. The cyanobacteria biomass for each ET-Class and each season was derived, thus representing a form of "virtual, season" in peri-Alpine lakes. The
winter season included samples from December, January and February; spring was defined from March to May, summer from June to August and autumn from September to November.