Ice in caves and its effect on thermal inversion and permafrost in the case of the Velika ledena jama v Paradani, Smrekova draga and neighbouring dolines

In the Velika ledena jama v Paradani, in the karstic blowholes on the slopes of Smrekova draga and in the nearby dolines I measured and interpreted air temperatures and the effect of the summer outflow of cold air from them into the surrounding area. In winter, cold air enters the cave, radically cooling the entrance part of the cave, where for this reason there is permanent cave ice. The summertime circulation is reversed: emerging from the inner part of cave, which has an average temperature of around 4° C, is air which only when it transits through the sub-cooled entrance part is then cooled to around 1° C. This air comes to the surface and in the hollow at the cave entrance maintains a distinct thermal inversion during the warm part of the year. There is a similar air circulation and similar development of annual temperatures observed at the vents, where cave air emerges through rubble spread over cave entrances on slopes or at the bottom of dolines. The stable summer air temperatures of around 1° C in the vents where I conducted measurements indicate that underneath them there is also permafrost or sub-cooled rock and permanent ice. This is created and preserved, just like in the caves, due to the advection of cold air in winter. In Trnovski gozd, such karstic permafrost is found at an altitude of 1,100 m above sea level. The outflow of cold air from the vents in the summer, just like inside the cave, causes a distinct thermal inversion in dolines on the surface.

FIRST REPORT OF HALOBACTERIA DOMINANCE IN A TROPICAL CAVE MICROBIOME

Scarce studies on microbial diversity in tropical caves have been published, a subterranean system still neglected from a microbiological point of view. Although most published studies are about temperate caves, usually archaeas and fungi have less attention than bacterial communities. Here, the microbiome structure and composition in a tropical cave system, as well the main environmental drivers, were studied during the wet and dry season. Soil and sediments from three different habitats at the cave (surface, entrance cave and dark zone) were sampled. Samples were characterized (temperature, air and substrate humidity, salinity, pH, nitrogen and organic carbon content, and chemical composition) and the microbiome was assessed by high-throughput sequencing, using amplicon sequencing (16S and ITS). Prokaryotic communities were dominated by Halobacteria, Actinobacteria and Bacilli, while fungal communities showed high abundance of Sordariomycetes. Microbiomes from the cave entrance, where a significantly elevated salinity levels were found, supported up to 63% of Haloarchaea compared to the other habitats studied. Differences in community structure were significant between habitats, but no influence of the season was observed. Main environmental drivers of community assembly included nitrogen and organic carbon content, temperature, and salinity. This is the first report of Halobacteria dominance in cave habitats, where they likely play important roles in nitrogen and phosphorus cycles. The cave entrance had lower diversity, but higher degree of microbial endemism, which characterize it as an important cave ecotone. The prevalence of heterotrophic microbial groups implies trophic structure based on detritivores, particularly in the dark zones. Our study brings new insights on microbiome composition in the underexplored tropical cave habitats.

It’s All about the Zone: Spider Assemblages in Different Ecological Zones of Levantine Caves

Caves possess a continuum of ecological zones that differ in their microhabitat conditions, resulting in a gradient of nutrients, climate, and illumination. These conditions engender relatively rapid speciation and diverse assemblages of highly specialised spider fauna. It is unclear, however, how zonation of these caves affects spider assemblage composition and structure. Surveys of 35 Levantine caves were conducted to compare the assemblages of spiders between their different ecological zones. The diverse spider assemblages of these caves differed between the entrance, twilight, and dark zones, with troglophiles and accidental species occupying the cave entrance, endemic troglobites occupying the dark zones, and hybrid assemblages existing in the twilight zones. The progression of assemblage composition and divergence throughout cave zones is suggestive of processes of ecological specialisation, speciation, and adaptation of cave-endemic troglobites in the deepest zones of caves, while cave entrance assemblages are composed of relatively common species that can also be found in epigean habitats. Moreover, the cave entrance zone assemblages in our study were similar in the different caves, while the cave dark zone assemblages were relatively distinct between caves. Cave entrance assemblages are a subset of the regional species pool filtered by the cave conditions, while dark zone assemblages are likely a result of adaptations leading to local speciation events.

Seasonal dynamics of Phlebotomus neglectus (Diptera: Psychodidae) in cave microhabitats in Romania and the rediscovery of Sergentomyia minuta (Rondani, 1843) after 50 years

Background In a countrywide study aiming to update the knowledge on diversity of sand fly species in Romania, a sand fly population was observed in an isolated system of cave microhabitats. The caves are located in the protected area of Canaraua Fetii, Dobrogea region, southeastern Romania. The highest sand fly diversity was recorded in this area between 1968 and 1970. This work presents a study conducted to estimate the seasonal variation of the sand fly species in correlation with the particular environmental factors of the isolated system of cave microhabitats. Methods Sand flies were collected between May and October 2020 from one trapping site of interest in Canaraua Fetii. The trapping site consisted of a cave entrance. CDC miniature light traps and sticky traps were used to collect insects from the exterior walls of the cave entrance. Species identification of collected sand flies was done using morphological keys. Statistical analysis of the trapping and climatic data was performed. Results From all collected sand flies, 99.7% (818/822) were Phlebotomus neglectus, 0.1% (1/822) Ph. balcanicus and 0.2% (2/822) Sergentomyia minuta. Sand fly activity was first observed on 2 July and last on 24 September. A monomodal abundance trend was present, with the peak activity between 16 and 17 July. The analysis of the climatic data showed correlations between the total number of captured sand flies and both average temperature and average relative humidity. The total number of collected specimens was statistically higher when CDC miniature light traps were used compared to sticky traps. The number of females on the sticky traps was significantly higher than the number of males on the same trap type. Compared with the sticky traps, significantly more males were collected by CDC miniature light traps. This is the first record of Se. minuta in Romania after 50 years of no records (despite the trapping effort of the last 5 years in the country). Also, Ph. sergenti, previously present in this location, was not found. Conclusions In the investigated natural habitat, the diversity of the sand fly species appears to have changed, with the predominance of Ph. neglectus instead of Ph. balcanicus and Se. minuta (recorded as the two predominant species in 1968–1970). A monomodal abundance trend was observed as in other regions of the country. The sand fly activity in this particular cave microhabitat appears to be longer than in other regions in Romania. Longer sand fly activity increases the zoonotic risk of various pathogenic species’ transmission, with an impact on public health, as sand flies are important insect vectors. Graphical abstract

Advancing Cave Detection Using Terrain Analysis and Thermal Imagery

Since the initial experiments nearly 50 years ago, techniques for detecting caves using airborne and spacecraft acquired thermal imagery have improved markedly. These advances are largely due to a combination of higher instrument sensitivity, modern computing systems, and processor-intensive analytical techniques. Through applying these advancements, our goals were to: (1) Determine the efficacy of methods designed for terrain analysis and applied to thermal imagery; (2) evaluate the usefulness of predawn and midday imagery for detecting caves; and (3) ascertain which imagery type (predawn, midday, or the difference between those two times) was most informative. Using forward stepwise logistic (FSL) and Least Absolute Shrinkage and Selection Operator (LASSO) regression analyses for model selection, and a thermal imagery dataset acquired from the Mojave Desert, California, we examined the efficacy of three well-known terrain descriptors (i.e., slope, topographic position index (TPI), and curvature) on thermal imagery for cave detection. We also included the actual, untransformed thermal DN values (hereafter “unenhanced thermal”) as a fourth dataset. Thereafter, we compared the thermal signatures of known cave entrances to all non-cave surface locations. We determined these terrain-based analytical methods, which described the “shape” of the thermal landscape, hold significant promise for cave detection. All imagery types produced similar results. Down-selected covariates per imagery type, based upon the FSL models, were: Predawn— slope, TPI, curvature at 0 m from cave entrance, as well as slope at 1 m from cave entrance; midday— slope, TPI, and unenhanced thermal at 0 m from cave entrance; and difference— TPI and slope at 0 m from cave entrance, as well as unenhanced thermal and TPI at 3.5 m from cave entrance. We provide recommendations for future research directions in terrestrial and planetary cave detection using thermal imagery.

Occurrence of the Black lace-weaver spider, Amaurobius ferox, in caves

Subterranean habitats house a wide range of species which show a number of adaptations to prevailing ecological conditions. Spiders are among the most abundant predators in caves; however, most studies on cave spiders focus on species adapted to these habitats. This is the first study related to the occurrence of the Black lace-weaver spider, Amaurobius ferox, in caves. The species lacks adaptations to the subterranean habitats and has been observed within meters from the cave entrance all year round, except in late winter until early spring. Furthermore, its occupancy is positively related to the presence of other three cave-dwelling spiders: Metellina merianae, Meta menardi and Tegenaria sp.

A preliminary survey of the abundance, diversity and distribution of terrestrial macroinvertebrates of Gcwihaba cave, northwest Botswana

Inventories of cave species and in-depth understanding of cave ecosystems are essential for informing conservation approaches for the unique and vulnerable cave fauna. Gcwihaba cave is the largest cave in Botswana but its ecology is poorly understood. This study set out to provide the first quantitative survey of the cave’s terrestrial macroinvertebrates. Macroinvertebrates were collected from sample sites at 10 m intervals into the cave from the cave entrance. At each site, macroinvertebrates on the cave floor were collected by quadrat sampling while macroinvertebrate from cave walls were collected by visual opportunistic searches. Moisture content, pH and electrical conductivity of the cave floor substrate were measured at each site to examine the influence of the floor properties on the distribution of macroinvertebrates on the cave floor. Twelve species in 10 families and 8 orders of terrestrial macroinvertebrates were collected. The occurrence of taxa varied across the sites, with most taxa occurring in the light and twilight sectors of the cave (within 30 m), whereas the dark sector (beyond 30 m) was dominated by cave cockroaches (Gyna sp.). The abundance of the cave cockroaches, darkling beetles (Tenebrionidae, Tenebrio sp.) and cave wasps (Sphecidae) positively correlated with floor substrate of high moisture content and high electrical conductivity, which became increasingly common with distance into the cave. The abundance of other taxa from the cave floor positively correlated with a floor substrate of high pH and low moisture, which was common near the cave entrance.

Preliminary report of the 2019 excavation at Švédův Stůl Cave in the Moravian Karst

Švédův Stůl Cave in the Moravian Karst has been excavated several times since Martin Kříž started the first excavation in 1886. Two parts of the site were re-excavated in 2019. The primary aim was to conduct classical as well as innovative and experimental sedimentological and geoarchaeological investigations of sediments from the discarded spoil heap outside the cave entrance (trench C–D). Intact sediments with a small number of lithic artefacts and a large number of animal bones were also excavated during the 2019 excavation (trench A–B) located under the trench excavated by Bohuslav Klíma’s team in the 1950s. An attempt is being made using pXRF, benchtop ED-XRF and ITRAX techniques to link some of the sedimentary material in the spoil heap (C–D) with the stratified sediments in trench A–B. Animal bones and lithic artefacts were found in both trenches. Numerous samples were collected for geoarchaeological, palaeoenvironmental and dating analyses and the results will be published in upcoming publications.

Discovery of a significant cave entrance in stripe karst, Horsethief Creek Group, Wells Gray Provincial Park, British Columbia, Canada

In April 2018, a significant cave entrance was recognized during an aerial survey in Wells Gray Provincial Park, British Columbia. A September 2018 assessment of the site confirmed one of the largest known, and previously undocumented, cave entrances in Canada. The feature is a large vertically walled sink swallowing a small river, likely leading to a spring 2.16 km horizontally from, and 460 m below, the sink. The entrance shaft was partially descended, surveyed, and found to have a volume of over 450 000 m3. Formed in a carbonate unit of the upper Proterozoic Horsethief Creek Group, the cave entrance occurs in stripe karst extending well beyond the known cave drainage. The disappearing river drains an area of 6.3 km2 in a valley containing two small glaciers. The river has a low flow (September) rate estimated at 0.3–0.5 m3/s, comparable with some of the largest sinks in Canada. Historic aerial photographs of the area show the entrance was hidden by perennial snowfields until regional climatic warming caused the snow plug to collapse sometime within the past decade.

A second new Amphipod species from the Peynirlikönü Cave (EGMA Cave): Gammarus egmao sp. nov. (Crustacea: Amphipoda)

Another new amphipod species, Gammarus egmao sp. nov., from Peynirlikönü Cave [Evren Günay Mehmet Ali Özel (EGMA) Cave] was identified. The specimens of the new species were sampled from 350 m inside of the cave entrance. This is the second species identified from the cave in addition to Gammarus ustaoglui Özbek and Güloğlu, 2005. The newly identified species has the following characteristic features: a) small eyes, b) 2- segmented accessory flagellum of antenna II, c) aesthetascs on the flagellar segments of antenna I, d) reduced armaments in distal part of palp of maxilla I e) short inner ramus of uropod III and reduced setation on margins of rami of uropod III. A detailed description of holotype female and illustrations of the appendages were presented. Additionally, differences from the related species were discussed.