Environmental assessment of freshwater ecosystems of the Sava River watershed and Cerkniško Lake, Slovenia, using the bioindicator species Fontinalis antipyretica: insights from stable isotopes and selected elements

Ten locations in the Notranjska region, Slovenia, with different land use in the catchment (town, village and agricultural areas), including reference points with different geological composition considered as unpolluted sites, were sampled for water and aquatic moss to evaluate environmental assessment in fresh water systems of the Sava River watershed. Samples of fresh water and Fontinalis antipyretica were taken in all four seasons during the years 2010 and 2012. The water chemistry of the investigated locations was dominated by , while concentrations of seasonally ranged from 2.1 to 6.4 mg L−1 and at one of the reference sites did not exceed 1.3 mg L−1. δ13CDIC values seasonally ranged from −13.3 to −8.1 ‰ and indicated waters dominated by degradation of organic matter and dissolution of carbonates. δ13Cplant values of F. antipyretica seasonally ranged from −45 to −32.9 ‰ and of δ15Nplant from −0.2 to 6.5 ‰. The higher δ15N value of 6.5 ‰ found in F. antipyretica was related to agricultural activity in the watershed. The content of minor and trace elements in F. antipyretica ranged from 4–38 µg g−1 for Ni, 17–105 µg g−1 for Zn, 2–28 µg g−1 for Pb, 0.26–1.95 µg g−1 for Cd, 4–27 µg g−1 for Cu, 4–49 µg g−1 for Cr, 1–6 µg g−1 for As and 0.33–3.24 µg g−1 for Se. The most polluted watershed was the Pšata stream (agricultural area, cattle farm with the highest concentration of nitrate in water) also with highest values for Ni, Cr, Pb, Zn and As.