Abiotic and biotic factors, especially microorganisms, play a role in the development of cave formations and the existence of unique characteristics of each cave. Due to the ecological conditions that characterize the cave environments, highly specialized microorganisms that are the main source of diverse bioactive compounds, inhabit these environments. The aim of this study is to determine the role and biotechnological potential of the bacteria isolated from Yarık Sinkhole located in Antalya (Turkey) by screening their ability to induce the CaCO3 precipitation, to hydrolyze urea, to induce calcite dissolution, and screening their possession of NRPS/PKS gene clusters. The most prevalent phylum is the Bacillota (synonym Firmicutes) (75.7 %), while the dominant species is Bacillus pumilus (33 %). All the isolates showed crystal formation on B4 agar medium, and the Energy dispersive X-Ray spectroscopy (EDS) analyses showed that the crystals are predominately composed of calcium, carbon and oxygen. Ninety-six (96 %) of our isolates have negative ureolytic activity. According to this result and having the ability to induce the CaCO3 precipitation, bac­teria in this environment use other biosynthesis pathways than urea hydrolysis. MgCO3 and CaCO3 were dissolved by 61 % and 59 % of the isolates, respectively. In addition, 5.9 % and 53.7 % of the isolates showed the possession of PKS and NRPS genes, respectively. This result reveals that our isolates have high in­dustrial and biotechnological potential. They may constitute good candidates for further biotechnological applications such as construction of bio-concretes, bioremediation, soil fertility, and production of biologically active secondary metabolites.

A microtremor survey based on ground surface data acquisition was used to identify and characterize the karst area of Cerme Cave, Yogyakarta, Indonesia, from the entrance to the exit of the cave. The entrance and exit of the cave are used as tie-in points because the characteristics of the two locations can be directly observed. Parameters used in this study include ground vibration amplification, shear wave velocity, and Poisson’s ratio. The presence of cavities can be characterized by a relatively strong contrast between these physical parameters and their surroundings. The exit of the cave, which can be considered as a sinkhole, has a dominant frequency of 3.2 to 4.6 Hz, which is relatively higher than that of the surrounding area. At the entrance of Cerme Cave, which has a large cavity, a small ground vibration amplification was detected, less than 0.1. The entrance and exit of the cave also exhibit a low shear wave propagation velocity of less than 350 m/s. The presence of a subsurface fluvial channel in Cerme Cave can be characterized by a high Poisson’s ratio of 0.4–0.5, a gain value of less than 0.1, and a shear wave velocity of less than 350 m/s.

In the Slovenian part of the Gulf of Trieste/Trst, submarine springs occur as funnel-shaped depressions in the Holocene sandy-silt marine sediment that forms the seafloor. These springs exhibit both elevated temperatures (up to 29.6 °C) and sulphur content. Based on their location, they are divided into three groups: the Izola group (three springs), the Bele skale group (two springs), and the Ronek group (seven springs). Previous investigations linked these springs to the Izola anticline, characterized by its limestone core and flysch limbs, but no detailed explanation was provided. We propose that: A) sulphur groundwater springs from the limestone (karstic aquifer) at the stratigraphic boundary with the flysch and B) springs occur in the nearshore area, where the sedimentary cover of Quaternary deposits is thin enough to be penetrated by spring waters and washed out. According to existing data, the anticline axis is NW-SE directed, and the Izola group lies approximately on the seaward extension of the axis. Therefore, this interpretation fits perfectly for the Izola group, while the Ronek and Bele skale groups are off-axis extensions and require reinterpretation. In order to resolve the micro-locations of the Ronek and Bele skale groups, we conducted a sedimentological logging of the flysch deposits and detailed geological mapping. The investigations revealed that: A) limestone outcrops occur only in the town of Izola, B) two prominent calciturbidite megabeds that occur in the flysch enable very detailed geological mapping, and C) the axis of the Izola anticline is oriented in the WNW-ESE direction, and this moderate anti-clockwise rotation of the anticline axis explains the micro locations of all springs. The Ronek and Bele skale groups are located on the southern side, and the Izola group is on the northern side of the limestone core of the Izola anticline.

Proper water resources management requires recognizing and evaluating the factors that affect the quantity and quality of water resources. The Ilam-Sarvak (Upper Cretaceous) and Asmari (Oligocene to Miocene) limestone- dolomite formations in the Zagros structural belt have formed a promising karst groundwater horizon. In the present study, the hydraulic relationship between the karst structures of the Izeh territory in the northeast of Khuzestan province was investigated using hydrogeochemical and isotopic information of springs and wells. The results enabled to understand various components influencing the recharge of water resources. In this study, samples were collected from the karst springs and wells of Mongasht, Shavish-Tanosh and Kamarderaz anticlines and Naal-e-Asbi (Horseshoe) syncline and meteoric water to understand the hydrochemical and isotopic characterization, and hydrogeological and hydraulic behavior of the Izeh karst system. The meteoric and groundwater samples were analyzed to determine major and minor ion concentrations and δ18O and δ2H isotope ratios. Isotopic content ranged from -31.6 to -2.9‰ and from -6.32 to -1.87‰ for δ2H and δ18O, respectively, and d-excess values were high and positive. The study of the isotopic content of water samples of springs and wells in the region shows three groups of water sources. The first group, related to the Mongasht anticline springs, has lower isotopic values, indicating that it is recharged by rainfall at high altitudes and snow melting. The isotopic value of the second group is richer than that of the first group, indicating rainfall recharge as well as groundwater mixing (ex­amples of Naal-e-Asbi syncline and Shavish-Tanosh anticline). The highest value in the third group (samples of Kamarderaz anticline) is attributed to evaporation and longer distance from the recharge site to the discharge point, as well as to the diffu­sion system. The trend of decrease in Sr+2 and increase in Ba+2 in the samples of dolomitic limestone formations (Shavish Ta­nosh and Mongasht anticlines) compared to the water samples of Kamarderaz anticline and Naal-e-Asbi syncline indicates the possibility that karst aquifers of the region are recharged from the Mongasht anticline and that there is a hydraulic relation­ship between these structures. D-excess and δ18O show a linear trend, illustrating the effect of altitude difference on isotopic content and recharge sources. The major and minor changes in the concentration of ions, the isotopic content of groundwa­ter and the relationship between TDS and δ18O and d-excess and δ18O indicate the mixing and recharging of karst aquifers (Shavish-Tanosh, Kamarderaz and Naal-e-Asbi aquifers) from the Mongasht karst aquifer and their hydraulic connection.

Report about the book on Lechuguilla Cave.

A 13-month monitoring was carried out in two caves that open up in the north-western sector of the Classical Karst (Gorizia Karst): Antro Casali Neri and Grotta Due Piani. In both, ß + γ radioactivity, radon and CO2 have a seasonal pattern, with maximums in summer and minimums in winter, even if their trends are somewhat different, due to the different morphological and thermal conditions. The increases begin when the outside temperature becomes higher than that of the caves and vice versa, decrease is recorded when outside temperature is below the cave temperature. The more modest daily variations of radon, on the other hand, are evident when its concentration is low. Sometimes they are related to meteorological variations or day/night rhythms, but, in other cases, they have no clearly identifiable causes. In Casali Neri cave the maximum radon activity was 50161 Bq/m3, while the CO2 concentration went off the instrument's scale (> 9999 ppm) only in the first days of August 2021. The highest radioactivity value was also recorded in this cave with 0.85 μSv/h (average of 8 minutes of recording), with peaks up to 1.05 μSv/h. In Due Piani cave, on the other hand, the radon activity was lower, with a maximum of 22138 Bq/m3, however, the CO2 values went off the scale from July to the first days of October 2021. In both cases, in the warm months, radon and CO2 appear to come mainly from the fractured rock of epikarstic zone. Further accumulations can then form in points with poor ventilation. Furthermore, research has shown that high concentrations of these two gases are not only typical of large or deep caves, but also of modest and easily accessible caves.

Microclimate conditions, mainly radiation, temperature and relative humidity vary according to cavities´ configurations and determine the microorganism’s colonisation. A meta-analysis was performed of environmental factors influencing the algal species colonisation in caves and rockshelters. For this purpose, the results of studies about algal colonisation in 82 caves and rockshelters in 11 European, Asian and American countries were analysed. Firstly, 412 species were counted of which Cyanobacteria predominated, followed by Chlorophyta and Bacillariophyta, and finally by Rhodophyta. The Shannon Index determined that the diversity of the algal species developing in these places was very high. The most diverse Cyanobacteria genera to appear in the different studied caves and rockshelters are Leptolyngbya with 28 different species, Gloeocapsa with 24 and Phormidium with 23. They are followed by Chroococcus with 18, Aphanothece with 14, Oscillatoria, Nostoc and Scytonema with 10 each and Schizothrix and Tolypothrix with 9 each. The most diverse Chlorophyta and Bacillariophyta genera are Chlorella with 9 different species and Diadesmis/Humidophila, Luticola and Nitzschia with 4, respectively. The principal component analysis revealed that both photosynthetically active radiation and relative humidity more actively conditioned the development of some algal species in cave environments than temperature.

Protecting groundwater in karst aquifers is extremely impor­tant. Vulnerability maps can greatly help proper decision mak­ing based on physical environmental attributes that influence how easily a contaminant applied to the land surface can reach groundwater due to anthropogenic activities, and the proper­ties of the contaminants. Methods for determining vulnerabil­ity based on the COST Action 620 Approach, when applied in the study area, may lead to contradictory results. The main purpose of this study is to provide an overview of academic research on intrinsic karst aquifer vulnerability methodologies applied in South American and Caribbean countries. Secondly, it describes studies related to karst aquifers that, in some cases, lack specific information on intrinsic vulnerability. The objec­tive is to encourage and to help develop specific methods for determining karst vulnerability in these regions. To achieve these purposes, a systematic literature review was conducted including studies conducted at institutions such as universities, national water institutes, and by geological services. Several methods have been used in the region such as COP, DRAS­TIC, RISK, EPIK, PI, PaPRIka, and the Slovene Approach. And some attempts have been made to develop a specific methodol­ogy that best suits the specificities of the region’s karst aqui­fers. South America and the Caribbean have almost 5 % of the world´s carbonate rocks. Some countries have large extensions of their territory covered by karst rocks, such as Peru, 15.4 %; Cuba, 67 %; and Mexico 25.29 %. Estimates indicate that more than 10 million people use water from karst systems in Mexico. In Cuba, 33 % of all available water volume originates from groundwater, and 91.51 % from karst aquifers. In Mexico, 13 studies have been conducted on the importance of karst aqui­fers, which mostly address the Yucatan Peninsula, followed by Brazil (9 studies), Cuba (5), Colombia (1) and Peru (1). Infor­mation about the theme is scarce in most of the other countries in the region. Some studies have incongruent results given the regional characteristics of tropical karst.

The development of emerging hollowing parts of the main channels of rinnenkarren systems at tributary channel junctions is interpreted in this study using Computational Fluid Dynamics (CFD) simulation. In the field, data from cross-sections of 505 local hollowings with one or more tributary channel junctions were investigated. The shift in the width–depth ratio of the local hollowings was studied as the number of junctions and the size of the hollowing changed. Flow was simulated through CFD in digital model channels, and the nature of the resulting vorticity was interpreted. Field data show that local hollowings emerging in the main channels of the channel systems at the junctions. In the main channels, when only a few tributary channels join in the vicinity of each other, local hollowings deepen during their growth and, most often, gradually become pits (depth is larger than width), as the morphometric analysis suggests. As the number of tributary channels increases, the local hollowing may develop into a kamenitza (width is larger than depth). The model experiment suggests the explanation that more tributary channel junctions result in more extensive vorticity, which contributes to the lateral extension (widening) of this channel section. The distance of the tributary junctions from each other also influences the downstream dimension of the local hollowing. In the field, the larger this distance, the more separated the local hollowings induced by individual tributaries. The model experiment suggests that this may occur because the intense vorticity generated by individual junctions becomes increasingly sectionalized as the tributary channel density decreases.