Carbon isotope fractionation in karst aquatic mosses.

Radiocarbon activity (aC) and C composition (C) were measured in hygrophyte and mesophyte (land) mosses collected in the natural habitat of the Plitvice Lakes and along the Zrmanja and Krupa Rivers (typical continental and Mediterranean climates, respectively), Croatia. aC and C values of mosses, of atmospheric CO and dissolved inorganic carbon (DIC) were compared with contemporary data and with data from 30 years ago at the Plitvice Lakes when C activity of atmospheric CO was ∼30% higher. A positive correlation between aC and C was observed for all data reflecting the change of carbon isotopic composition in DIC along the water flows and in atmospheric CO regardless of the climatic regions and historic period. Fraction of the atmospheric carbon in moss and carbon fractionation factor from aquatic CO (DIC) to moss tissue were calculated for each individual moss. Three species of mosses had  ∼ 0 % implying that they turn to anabiosis during dry periods. The relation differentiates true aquatic and amphiphyte mosses. The first had a statistically significant negative correlation between and . The amphiphyte mosses had lower with higher water flow rates.