Using extracellular enzyme activities as a main functional indicator, we tried to understand if heterotrophic microbial communities adapted to hypersaline conditions are fully functional despite the stressors they must face. Moreover, we studied how natural salinity fluctuations may affect this functioning. Thus has been done by sampling 4 hypersaline lakes in different moments, obtaining a natural hypersaline gradient. The study include physicochemical water parameters, extracellular enzyme activities, life to dead prokaryote ratio, photosynthetic pigments content, DOM quality and quantity indices, DOC, and TN.