Underground tourist cultural and natural heritage sites in Slovenia that share similar management problems with other such sites worldwide include Postojna Cave with more than a half million annual ...visitors and the UNESCO World Heritage Site Škocjan Caves. The underground environment is challenged by ultrasonic noise derived from different electric devices in a broad range (10–123kHz) that can be minimised with protective housings. Lamps which increase temperature and lower relative humidity should be omitted. Chlorella vulgaris thrived very well under a halogen lamp and LEDs whose spectra were modified to give a natural appearance to illuminated features and emitted photon quanta close to the photosynthetic compensation point (∼20μmolphotons/m2s). Remediation of insensitive calcite surfaces colonised by lampenflora with a 15% (v/v) solution of hydrogen peroxide (pH 7.0–7.5) was successful. Because visitors introduce and spread, especially by footprints, many live microorganisms (>10000 colony-forming units per 100cm2), measures to reduce such input should be implemented. Bacterial counts expressed as colony-forming units per m3 were more indicative for the presence/absence of tourists than were changes in carbon dioxide concentration. Not only tourists, but also external climatic conditions influenced the concentration of airborne bacteria. Microbiological parameters should be included in estimating tourist carrying capacity for sensitive underground sites.
The 17th ISME was held in Leipzig, Germany. During the symposium eight plenary lectures, 26 different sections and three days of poster presentations were organized. A participant could choose one of ...six or seven simultaneously running sections daily which covered an extremely wide set of microbial ecology from evolution, modeling of microbial interactions, review on new and existing metabolic pathways, (meta)genomics, interactions between microbes and hosts, biogeochemical cycles, bioinformatics, new methods and innovative bioremediation procedures. It became clearly evident that microbial ecology can offer some answers to many urgent global issues. Here, Mulec presents some interesting highlights from the symposium.
A mixture of coal bottom ash and slag, with a fraction of fly ash (CAFAS) from steam locomotives, was placed in the cave Divaška jama to delimit and level tourist trails. Emplacement began in 1914 ...and carried on for several decades. The CAFAS mixed with other cave material gradually changed its structure and appearance. Currently the concentration of some elements in the CAFAS (As, Cu, Hg, Ni, Pb, Zn), and also to a lesser extent in cave sediments (Cr, Cu, Ni), indicates a possibly harmful effect on sediment-associated biota based on ecotoxicological assays. Compared to the cave sediment, the CAFAS contains distinctly different mineral phases and presents a different source of radioactivity. Microbial metabolic activity of CAFAS is low, 0.22 μl O
/gDW h, but higher than that of cave sediment. The present environmental hazards from CAFAS are estimated to be low. Whereas the emplacement of CAFAS was seen initially a long-term solution for waste disposal and management of the cave, it turned out that CAFAS enriches the underground environment with inorganic and organic compounds and disperses pollution into the cave ecosystem. After its removal from the cave, the CAFAS should be investigated thoroughly due to its susceptibility to alteration.
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.
Predicting variations in dissolved oxygen concentration (DO) is important for management and environmental monitoring of aquatic ecosystems. Regression analyses and univariate and multivariate ...time-series analyses based on autoregressive methods were performed to investigate oxygen conditions in the Pivka River, Slovenia. The monitoring site was established upstream where the river sinks into the karst cave Postojnska jama, which hosts one of the richest subterranean faunas yet studied worldwide. It was found that abnormal variations of DO started to be noticeable at values of DO < 3 mg/L and became more pronounced until the ecosystem reached fully anoxic conditions. The abnormal fluctuations during the critical summer period were due to environmental conditions, organic load and resident biota. Predictions for future detection of anomalies in DO values were made from stable residuals of the measured data, and it was demonstrated that the model could be used to obtain a reliable estimate for a short period, such as one day. The example presented an analysis pipeline based on specific and established threshold DO values, and it is particularly important for ecosystems with diversity hotspots where prolonged low DO values can pose a threat to their biota.
Speleotherapy is one of the non-pharmacological methods for the treatment and rehabilitation of patients with chronic respiratory diseases, especially those with chronic obstructive pulmonary disease ...(COPD) and asthma. On the one hand, one of the alleged main advantages of speleotherapeutic caves is the low microbial load in the air and the absence of other aeroallergens, but on the other hand, due to the lack of comprehensive air monitoring, there is little information on the pristine and human-influenced aerobiota in such environments. The aim of this study was to assess the anthropogenic effects of speleotherapy on the air microbiota and to investigate its potential impact on human health in Sežana Hospital Cave (Slovenia). From May 2020 to January 2023, air samples were collected in the cave before and after speleotherapeutic activities using two different volumetric air sampling methods—impaction and impingement—to isolate airborne microbiota. Along with sampling, environmental data were measured (COsub.2, humidity, wind, and temperature) to explore the anthropogenic effects on the aerobiota. While the presence of patients increased microbial concentrations by at least 83.3%, other parameters exhibited a lower impact or were attributed to seasonal changes. The structure and dynamics of the airborne microbiota are similar to those in show caves, indicating anthropization of the cave. Locally, concentrations of culturable microorganisms above 1000 CFU/msup.3 were detected, which could have negative or unpredictable effects on the autochthonous microbiota and possibly on human health. A mixture of bacteria and fungi typically associated with human microbiota was found in the air and identified by MALDI-TOF MS with a 90.9% identification success rate. Micrococcus luteus, Kocuria rosea, Staphylococcus hominis, and Staphylococcus capitis were identified as reliable indicators of cave anthropization.
A commercially available adenosine triphosphate (ATP) detection system (Hygiena, USA), supported by cultivable microbial indicators, was used to estimate bioburden in different habitats in and ...outside show caves: air, water and solid surfaces. A strong positive correlation between ATP concentration expressed as Relative Light Units (RLU) and Colony-Forming-Units (CFU) was observed for swab samples from cave surfaces. In terms of ATP units, surfaces in a single cave system (Postojna Cave) varied considerably (240-1,258,800 RLU/ 20 cm^sup 2^) and commonly exceeded the bioburden level of analogues on the surface (0-114,390 RLU/ 20 cm^sup 2^). Cave sub-habitats were colonized by physiologically distinct microbial communities in terms of their nutrient demands, temperature requirements and r/K growth strategy. The highest ATP biomass indicator (1,258,800 RLU/ 20 cm^sup 2^) for the speleothem that had been touched but accompanied with comparable concentration of CFU (~10^sup 6^ CFU/ 20 cm^sup 2^) for other cave sub-habitats, can be related to the presence of deposited human epithelium skin cells. Show cave infrastructures containing heavy metals, e.g. copper used in safety fences, reduce the viability of microbiota. Mass cave visitation and the presence of allochthonous organic matter result in high levels of airborne and total biomass. Once such material becomes airborne, the location of its settling depends upon natural and human-induced air movements. Underground habitats play an important role in the preservation and concentration of microbial biomass using air and water as transport mechanisms.
Informal cooperation between Slovenian and Chinese karstologists started as early as 1980's, but the main boost was initiated after 1995 in the frame of several national and international projects. ...Fruitful long-term cooperation between the Karst Research Institute, Research Centre of the Slovenian Academy of Sciences and Arts, and Yunnan Institute of Geography, Yunnan University, successfully culminated in many joint research efforts, among which the research in Stone Forest (Shilin) in South China Karst was the most apparent one. Tourist visitation of the area, which has been protected since the 1930's, has risen significantly after 1978, when the territory was officially open for tourism. Close cooperation between Slovenian and Chinese researchers supported to unravel some mechanisms in the evolution of these natural phenomenon. The results assisted the successful candidature of Shilin's designation as UNESCO World Heritage Site in 2007.
Subterranean calcite dissolution and precipitation are often considered as strictly geochemical processes. The active involvement of microbes in these processes is commonly underestimated in the ...literature due to general oligotrophic conditions in caves, except in particular cave conditions, such as sulfidic caves and moonmilk deposits, where the presence of microbes likely plays a key role in mineral deposition. Here, we study the possible involvement of microbes from Postojna Cave, Slovenia, in carbonate dissolution (litholysis) and precipitation (lithogenesis). Microbes were sampled from small pools below hydrologically diverse drip sites and incubated on polished limestone tablets at 10 and 20°C for 2 and 14 weeks under cave-analogue conditions. The tablets were then observed under scanning electron microscope to investigate microbe–rock interactions. Our experiments showed the presence of various microbial morphotypes, often associated with extracellular polymeric substances, firmly attached on the surfaces. Unfortunately, our surface sterilization method using 96% and 70% ethanol could not establish the complete aseptic conditions in deep natural cracks in the experimental limestone tablets. Nonetheless, our results emulate the interaction of environmental microbes with limestone rock. Conspicuous calcite dissolution and precipitation were observed in association with these microbes. Furthermore, we show evidence of entombment of microbes in a Si-rich precipitate during nutrient-depleted growth conditions and we suggest that microbial involvement in silica mobilization under ambient conditions may be a widespread and often overlooked phenomenon. Our findings have important implications for microbial-mediation of cave carbonate dissolution and precipitation, including the preservation of past climate proxy signals in speleothems and prehistoric cave art. Improvements to the methodology and further work are suggested to enable more robust
ex-situ
cultivation experiments in the future, facilitating better and more detailed research into this topic.
(1) Background: Airborne microbes are an integral part of a cave ecosystem. Cave allochtonous airborne microbiota, which occurs mainly during aerosolization from an underground river, from animals, ...and from visitors, is particularly pronounced in show caves. The impacts of tourists and natural river aerosolization on the cave air were estimated in large cave spaces within the Škocjan Caves; (2) Methods: Simultaneously with the measurements of atmospheric parameters, cultivable airborne bacteria were impacted, counted and identified using MALDI-TOF MS (Matrix-Assisted Laser Desorption/Ionization Time-Of-Flight Mass Spectrometry); (3) Results: A mix of bacteria typically associated with humans and with natural habitats, including a large percentage of non-identified isolates, was found in the cave air. Few of the isolates were attributed to Risk Group 2. A strong positive correlation between tourist numbers and the rise in the concentration of airborne bacteria was indicated. Concentration of airborne bacteria rises to particularly high levels close to the underground river during periods of high discharge. A 10-times lower discharge reflected an approximately 20-times lower concentration of airborne bacteria; (4) Conclusions: Caves that are open and visited contain a diverse airborne microbiota originating from different sources. Enormous cave chambers that display relatively dynamic cave climate conditions do not normally support the enhancement of airborne bacterial concentrations.
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