Microbiota entrapped in recently-formed ice: Paradana Ice Cave, Slovenia

Abstract

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.

Emerging Ecotone and Microbial Community of a Sulfidic Spring in the Reka River near Škocjanske Jame, Slovenia

“…For comparison, values of stable isotopes were aligned along the local meteoric water line for Postojna. Monthly composite precipitation samples were collected in Postojna (45 • 46 31.55 N, 14 • 12 47.64 E, 553 m a.s.l., about 21 km from the Smrdljivec spring) between August 2015 and October 2017 [34].…”

The hidden microbial ecosystem in the perennial ice from a Pyrenean ice cave

“…These environments represent a small portion of the total cryosphere ( Kern and Perşoiu, 2013 ), yet they are an important source of paleoclimate and paleoenvironmental information ( Kern et al, 2009 ; Stoffel et al, 2009 ; Feurdean et al, 2011 ; Spötl et al, 2013 ; Perşoiu et al, 2017 ; Sancho et al, 2018 ; Leunda et al, 2019 ; Racine et al, 2022 ) that is under imminent risk of disappearance ( Kern and Perşoiu, 2013 ; Perşoiu et al, 2021 ; Wind et al, 2022 ). Over the last years, ice caves have awakened interest as places to study both modern and fossil ice microbiota communities ( Iţcuş et al, 2016 ; Brad et al, 2018 ; Iţcuş et al, 2018 ; Mondini et al, 2019 ; Paun et al, 2019 , 2021 ; Mulec et al, 2021 ). Still, the bacterial diversity of ice caves has been barely explored.…”