Karst Research Institute, Research Centre of the Slovenian Academy of Sciences and Arts, Titov trg 2, 6230, Postojna, Slovenia.
UNESCO Chair on Karst Education, University of Nova Gorica, Glavni trg 8, 5271, Vipava, Slovenia.
Sci Rep. 2021 Jan 21;11(1):1993. doi: 10.1038/s41598-021-81528-6.
Paradana is one of the biggest ice caves in Slovenia, with an estimated ice volume of 8,000 m. 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 (O, H) 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 × 10 to 1.52 × 10 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.
帕拉达纳是斯洛文尼亚最大的冰洞之一，估计冰量为 8000 立方米。反映气候条件，洞穴冰经历了反复的冻融循环和每年定期的新冰沉积。从 2016 年 5 月冻结的湖泊中采集了三个不同的冰块样本，以获取有关冰物理化学性质和相关微生物群落组成的数据。冰样本的同位素组成（O，H）和为波斯特伊纳每月降水构建的本地大气水线（LMWL）用于估计形成冰的水的同位素组成，其氘过剩值较高，氯、硫酸盐和硝酸盐浓度较低。冰块内总有机碳（1.93-3.95mg/l）的值在测量的岩溶溪流范围内。冰内的总细胞计数很高，细胞活力的比例随着深度梯度的增加而增加，范围从 4.67×10到 1.52×10细胞/ml，分别为 51.0%到 85.4%。变形菌门是洞穴冰微生物组的核心（55.9-79.1%），可能在这个生态系统中发挥着重要作用。放线菌是第二丰富的门（12.0-31.4%），其次是拟杆菌门（2.8-4.3%）。记录的冰型达到 442 属，但只有 43 属的丰度大于 0.5%。最丰富的是假单胞菌，一种著名的冰栖生物，以及以前未在这种环境中报道过的 Lysobacter。最后，从冰中培养出两种黄藻，即来自极地环境的 Chloridella glacialis 和 Ellipsoidion perminimum。这表明，在这种环境中，光养生物的丰度和生态作用可能比以前推断的要大。
