Semi-natural springs contain complex com- munities of living organisms that look for constant water supplies. However, an ex- cess of nitrate in the underlying aquifers could affect species richness, especially of those groups that are sensitive to pol- lution such as bryophytes (mosses and liv- erworts). In this study, we analyse water characteristics and presence of bryophytes in 93 natural springs in Lluçanès region. We find that although a few species can cope with a relative nitrate excess, most of them do not tolerate it, meaning that spe- cies richness decreases in the most polluted sources, showing an adverse effect of water pollution on the biodiversity of bryophytes.