Environmental conditions of alpine springs of the upper Po River (NW Italy) on the basis of their epilithic diatom communities

Diatom (Bacillariophyceae) assemblages were sampled in 7 springs in the upper part of the River Po basin in the summer of 2010. Four springs are situated in the mountainous part of the study area while three are in the lowland plain. Chemical-physical variables were measured and analyzed in water samples of 6 springs. 101 diatom species were identified in the surveyed springs, with species richness ranging from 12 to 52. Gomphonema nathorstii, described for arctic regions, was found in Italy for the first time. Multivariate statistical analysis was undertaken to link taxonomical and environmental data, and indicated the existence of three distinct environmental features, each one characterized by prevalent diatom species: 1) low pH and high dissolved oxygen, 2) both high pH and dissolved oxygen and 3) high levels of silica and conductivity.