RESUMO
Paradana is one of the biggest ice caves in Slovenia, with an estimated ice volume of 8,000 m3. Reflecting climatological conditions, the cave ice undergoes repeated freeze-thaw cycles and regular yearly deposition of fresh ice. Three distinct ice block samples, collected from the frozen lake in May 2016, were analysed to obtain data on ice physicochemical properties and the composition of associated microbiota. Isotopic composition of the ice samples (18O, 2H) and a local meteoric water line (LMWL) constructed for monthly precipitation at Postojna were used to estimate the isotopic composition of the water that formed the ice, which had high values of deuterium excess and low concentrations of chloride, sulphate and nitrate. The values of total organic carbon (1.93-3.95 mg/l) within the ice blocks fall within the range of those measured in karst streams. Total cell count in the ice was high and the proportion of cell viability increased along the depth gradient and ranged from 4.67 × 104 to 1.52 × 105 cells/ml and from 51.0 to 85.4%, respectively. Proteobacteria represented the core of the cave-ice microbiome (55.9-79.1%), and probably play an essential role in this ecosystem. Actinobacteria was the second most abundant phylum (12.0-31.4%), followed in abundance by Bacteroidetes (2.8-4.3%). Ice phylotypes recorded amounted to 442 genera, but only 43 genera had abundances greater than 0.5%. Most abundant were Pseudomonas, a well-known ice dweller, and Lysobacter, which previously was not reported in this context. Finally, two xanthophytes, Chloridella glacialis and Ellipsoidion perminimum, known from polar environments, were cultured from the ice. This indicates that the abundance and ecological role of phototrophs in such environments might be greater than previously deduced.
RESUMO
Syringes are the most expensive consumables for analyses in the Liquid Water Isotope Analyser using commercial Cavity Ring-Down Spectroscopy (CRDS) systems. Our experience shows that although the syringe life significantly varies, it is not an exception that a syringe performs many thousands of injections. A simple maintenance procedure consisting of replacing the syringes two times per day and keeping them in the deionised water resulted in an average syringe life of over 3500 injections. Number of injections per sample affects the between-sample memory effect and the cost of the analysis (duration, energy, consumption of syringes). We studied the influence of the number of injections (six and nine) on the final δ(18)O and δ(2)H values using two sets of samples covering the ranges of isotopic composition typical for the natural waters of the highest part of the Carpathians (streams, springs, soil water and precipitation). The differences in the final δ-values between nine and six injections were within 0.1 for δ(18)O and 1.0 for δ(2)H for the Picarro 2120i and 2130i CRDS systems.