Microorganisms colonize caves extensively, and in caves open for tourism they may cause alterations on wall surfaces. This is a major concern in caves displaying Paleolithic art, which is usually ...fragile and may be irremediably damaged by microbial alterations. Therefore, many caves were closed for preservation purposes, e.g. Lascaux (France), Altamira (Spain), while others were never opened to the public to avoid microbial contamination, e.g. Chauvet Cave (France), etc. The recent development of high-throughput sequencing technologies allowed several descriptions of cave microbial diversity and prompted the writing of this review, which focuses on the cave microbiome for the three domains of life (Bacteria, Archaea, microeukaryotes), the impact of tourism-related anthropization on microorganisms in Paleolithic caves, and the development of microbial alterations on the walls of these caves. This review shows that the microbial phyla prevalent in pristine caves are similar to those evidenced in water, soil, plant and metazoan microbiomes, but specificities at lower taxonomic levels remain to be clarified. Most of the data relates to Bacteria and Fungi, while other microeukaryotes and Archaea are poorly documented. Tourism may cause shifts in the microbiota of Paleolithic caves, but larger-scale investigation are required as these shifts may differ from one cave to the next. Finally, different types of alterations can occur in caves, especially in Paleolithic caves. Many microorganisms potentially involved have been identified, but diversity analyses of these alterations have not always included a comparison with neighboring unaltered zones as controls, making such associations uncertain. It is expected that omics technologies will also allow a better understanding of the functional diversities of the cave microbiome. This will be needed to decipher microbiome dynamics in response to touristic frequentation, to guide cave management, and to identify the most appropriate reclamation approaches to mitigate microbial alterations in tourist Paleolithic caves.
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•High-throughput sequencing is shedding new light on the cave microbiota.•Cave exploration at a finer taxonomic level is needed to assess microbial endemism.•Bacteroidetes and Nitrospirae might serve as bio-indicators of cave anthropization.•Tourism may cause significant shifts in the microbiota of Paleolithic caves.•Tourism-related microbial alterations require further research attention.
Slovenia is considered as the cradle of karst geotourism as cave tourism started there as early as the Middle Ages. To date more than 12,000 caves were discovered from which 22 have the status of ...tourist caves. From these, 10 were assessed using the M-GAM model (Modified Geosite Assessment Model) to gain information for better future management strategies. The results show that visitors of Slovenian tourist caves mostly appreciate their natural values, as they prefer caves without major tourism infrastructure and they pay attention to their protection status. The model also confirmed that the two most important tourist caves (Postojna Cave and Škocjan Caves) have the leading geotourism role and that the management of tourist caves via a regional park as is the case of Škocjan Caves is an example of good practice.
•Artificial lights in caves allow the establishment of photosynthetic organisms.•We tested the response of lampenflora in two show caves with different tourist flux.•Lampenflora growth was higher in ...the cave with longer lighting duration.•Higher light intensity corresponds to higher proliferation of lampenflora.•Modulating the lighting regime can effectively help in controlling lampenflora growth.
When artificial lighting systems are installed in show caves, alien photosynthetic epilithic prokaryotic and eukaryotic microorganisms —the so-called ‘lampenflora’— form extended biofilms on cave speleothems, causing structural and aesthetic damage. Among the environmental drivers influencing their proliferation, light intensity and duration of illumination are expected to play a key role. To unravel which environmental variables determine the proliferation of lampenflora, we designed a specific study in two Italian show caves with similar characteristics and management practices, but differing in terms of tourist use and thus in terms of duration of illumination. In each cave, we selected multiple illuminated speleothems at progressive distance from the cave entrance where we measured the chlorophyll-a concentration of the three main microorganism groups constituting phototrophic biofilms, namely cyanobacteria, diatoms and green algae, by means of the portable fluorimeter BenthoTorch®. In each sampling plot we also recorded the intensity of artificial lights and we visually evaluated the presence of seeping water on speleothems. By adopting advanced regression techniques, we revealed that the total chlorophyll-a and the concentration of the three groups differ between caves, increasing in the cave with higher number of visitors. Regarding the other environmental factors, light intensity positively influenced the total chlorophyll-a and the concentration of cyanobacteria, while humidity increased diatom concentration. We then provided suggestions to implement appropriate management actions addressed to the modulation of the lighting regime in show caves, especially in the areas most exposed to the proliferation of lampenflora.
No Brasil há mais de 20 mil cavernas registradas no Cadastro Nacional de Informações Espeleológicas (CANIE), das quais algumas centenas são usadas de modo formal ou informal para a visitação ...turística e apenas 44 contam com o instrumento formal que regula a gestão deste uso, o Plano de Manejo Espeleológico (PME). Isso implica em aspectos positivos e negativos para o setor e desafios para as entidades gestoras de cavernas turísticas, públicas e privadas. Diante disso, esta investigação foi realizada com o objetivo de apresentar propostas para ampliar a sustentabilidade do espeleoturismo no país. Trata-se de um estudo de caso sobre cinco cavernas turísticas localizadas em Minas Gerais. A coleta de dados ocorreu através da revisão da literatura e da pesquisa de campo, que envolveu observação direta e entrevista semiestruturada com os gestores utilizando como instrumento um questionário. Posteriormente, os dados foram organizados e interpretados utilizando a análise de conteúdo como método. Os resultados obtidos ressaltam as potencialidades e as limitações de cada tipo de gestão de caverna turística, e constatam que a sustentabilidade do espeleoturismo no Brasil será atingida por meio da consolidação de parcerias efetivas entre o governo e as entidades privadas.
The conversion of wild caves into tourist sites poses serious threats to the conservation of subterranean environments. Among them, the extensive growth of photosynthetic biofilms induced by ...artificial lighting—the so-called
lampenflora
—is of particular concern for cave managers. The identification of cost-effective management actions controlling the growth of
lampenflora
is therefore required to preserve the environmental and touristic values of show caves. By taking advantage of the closure period imposed to contain the COVID-19 pandemic, we tested whether 6 months of cave closure could be an effective strategy to reduce the concentration of photosynthetic biofilms on speleothems in four geographically close Italian show caves. We compared the concentration of the three main microorganism groups composing
lampenflora
, i.e., cyanobacteria, diatoms, and green algae, measured in September 2020 with values recorded 6 months after the closure, in May 2021. Although slight variations have been observed across the different sampling sessions, we did not detect any significant effect of the closure period on the overall concentration values of
lampenflora
. Also, we recorded no significant differences in
lampenflora
concentration after 4 months of regular tourist use, in September 2021. Our results suggest that management practices based on regulating visits to show caves are not effective strategies to reduce
lampenflora
. Therefore, management practices aiming at a sustainable use of show caves should focus on the active removal of photosynthetic biofilms.
Microplastic particles are a global problem, which has been widely found in marine and terrestrial environments. However, microplastic pollution in caves and karst aquifers is still poorly studied. ...To improve the current knowledge of microplastic pollution, we investigated the sediments of a show cave in Italy. We developed a methodology based on a cave-adapted version of the methods used in several studies to detect microplastics from sediments of different environments and with various laboratory tests. The microplastics were extracted from sediments via density separation and subjected to organic matter removal. Filters were observed with and without UV light under a microscope, before and after organic matter removal, and the microplastics were characterised according to shape, colour, and size, with visual identification. About 55% of the fibres observed under the microscope on filters were removed via organic matter removal. An average of 4390 items/kg dry weight was calculated for the touristic zone and 1600 items/kg dry weight for the speleological/research section. Fibre (84.9%) was the most abundant shape, and most microplastics were smaller than 1 mm, accounting for 85.4%, of which 58.4% were shorter than 0.5 mm. The highest microplastic abundance was fluorescent under UV light (87.7%); however, 12.3% of the microplastics observed on filters were not fluorescent. Most fluorescent fibres were transparent (84%), whereas blue (46.1%) and black (22.4%) fibres were more common for the non-fluorescent ones. Our results highlight the presence of microplastics in show caves, and we provide a valid non-invasive and non-expensive analytical technique for the preparation and isolation of microplastics from cave sediments, giving useful information for evaluating the environmental risks posed by microplastics in show caves.
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•Show caves are polluted by microplastics.•An average of 4390 microplastics/kg has been found in cave sediment.•Small size and fibre shape microplastics are the most common particles.•The majority of particles are fluorescent under UV light.•A potential environmental impact arises from microplastics in cave.
Following the declaration of the COVID-19 pandemic, the Spanish Government restricted non-essential movements of all citizens and closed all public spaces, such as the Nerja Cave, until May 31, 2020. ...This particular condition of the closure of the cave provided a unique opportunity to study the micro-climate conditions and carbonate precipitation in this tourist cave without the presence of visitors. Our results show the significant effect of visitors on the air isotopic signature of the cave and on the genesis of the extensive dissolution features affecting the carbonate crystals formed in the tourist sector of the cave, alerting us to the possible corrosion of the speleothems located there. The movement of visitors within the cave also favours the mobilisation of aerial fungi and bacterial spores and their subsequent sedimentation simultaneously with the abiotic precipitation of carbonates from the drip water. The traces of these biotic elements could be the origin of the micro-perforations previously described in the carbonate crystals formed in the tourist galleries of the cave, but they are subsequently enlarged due to abiotic dissolution of the carbonates through these weaker zones.
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•Cave closure due to the pandemic (coronavirus) has allowed the study of its pristine conditions.•Visitors, spores and bacteria condition the texture of carbonate precipitates.•Some micro-cavities are induced by micro-organisms during crystal formation.•Anthropogenic CO2 enlarges micro-cavities of biotic origin.•The isotopical signature of the soil and vadose air is constrained.
On May 27, 2008, a strong earthquake of magnitude 5.3 Richter hit Zanjan province. The radon concentration has been measured and registered at the time of earthquake occurrence at 10:48 local time ...inside the Katalekhor cave being situated at suburb of Zanjan city. After this event, it was planned to measure and analyze the radon concentration in the same year (2008) and 10 years after the earthquake (2018) by using passive methods and the results have been presented. Real time observations show an increase of five times in radon concentration when earthquake happened comparing to normal condition.
The International Commission on Radiological Protection (ICRP) issued its Publication 137, Occupational Intakes of Radionuclides: Part 3 in which the radon equilibrium factor is fixed as 0.4 for ...tourist caves; however, several studies have reported a different value for the factor and its seasonal variation has also been observed. In this study, the radon concentration, equilibrium equivalent radon concentration and meteorological data were measured, and the equilibrium factor was evaluated in a tourist cave, Gyokusen-do Cave located in the southern part of Okinawa Island in southwestern Japan. Radon concentrations were measured with an AlphaGUARD and their corresponding meteorological data were measured with integrated sensors. Equilibrium equivalent radon concentration was measured with a continuous air monitor. The measured radon concentrations tended to be low in winter and high in summer, which is similar to previously obtained results. By contrast, the equilibrium factor tended to be high in winter (0.55 ± 0.09) and low in summer (0.24 ± 0.15), with a particularly large fluctuation in summer. It was concluded that measurements in different seasons are necessary for proper evaluation of radon equilibrium factor.
Subterranean environments are essential for the survival of many bat species and other cave fauna but these places are subject to increasing human disturbance. To examine the significance of ...subterranean habitats for the conservation of bats in China we surveyed bat species in 225 underground sites during 2003–2011. Our results show that 77% of bat species in China, including 30 nationally Endangered or Vulnerable species and nine endemic species, roost in caves and other subterranean habitats. The number of species in occupied roosts was 1–15. Almost 90% of the roosts surveyed contained signs of human disturbance, most of which was from recreational activities. One hundred and twenty-one roosts merit special concern because they harbour ≥ 6 species or > 1,000 individuals, or species of special concern (threatened or endemic species). Generally, larger roosts support more species and a greater abundance of bats than smaller roosts but there is no direct correlation between the presence of species of special concern and roost size. Disused tourist caves have significantly more bat species than other types of roosts. Our data demonstrate that roost disturbance by recreational activities has pronounced detrimental effects on the number of bat species and the presence of species of special concern. We discuss the social, economic and political issues that could adversely affect bat conservation in caves in China, and we recommend that protection of subterranean habitats should be a high priority for bat conservation.
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