Geochemical characterization of clastic sediments sheds light on energy sources and on alleged anthropogenic impacts in cave ecosystems

Caves are usually oligotrophic ecosystems, where the organic matter represents a limiting factor to the hypogeal community and sediments are often a significant energy source. With a view to identifying the energy input influencing the ecological processes occurring in caves, as well as the potential alteration sources of the natural equilibriums, geochemical features of several typologies of clastic sediments from the Pertosa-Auletta Cave (Italy) were investigated. The collected sediments, analyzed for a number of chemical (organic matter, Al, B, Ba, Ca, Cd, Co, Cr, Cu, Fe, K, Li, Mg, Mn, Mo, Na, Ni, P, Pb, S, Si, Sr, Ti, V, Zn concentrations) and mineralogical (quartz, calcite, dolomite, clay minerals) characteristics, showed a different composition. Overall, their origin is supposed to be allochthonous, related to the important fluviokarst activities interesting the cave in the past, whereas the abundance of calcitic and dolomitic compounds can be autochthonous, being the carbonate the main host rock. The highest concentrations of organic matter, together with C, Cu, Mo, N, P, Pb, S and Zn, highlighted in one sample composed mainly of bats guano, revealed an important bioavailable energy input as well as a pollutant accumulation, mainly of anthropogenic origin.

Bacterial diversity in vadose cave pools: evidence for isolated ecosystems

Microbial diversity of cave pools, especially vadose pools, has received relatively little attention. To help fill this gap, this study reports on the bacterial diversity of 17 pools in three New Mexican arid land caves: Carlsbad Cavern, Lechuguilla Cave, and Hell Below Cave. These pools are spread throughout the caves and, with two exceptions, are not connected. The pools share a basic water chemistry, with fresh water of the calcium-magnesium-bicarbonate type. These 17 pools have Chao1 values between 40 and 1738; the Shannon diversity averages 4.6 ± 1.1, ranging from 2.6 to 6.4; and the Simpson averages 0.881 ± 0.099, ranging from 0.622 to 0.981. No two pools had the same communities, even at the phylum level. Nitrospirae, Alphaproteobacteria, Betaproteobacteria and Gammaproteobacteria were found >5% abundance in nine or more cave pools. Actinobacteria, Chloroflexi, Fibrobacteres, Firmicutes and Plantomycetes were at >5 % in four to six pools. Of the top ten widespread bacterial genera, Nitrospira was found in all pools, with >5 % in eleven pools. Other common genera include Polyclorovans, Propionibacterium, Polaromonas, Haliangium, Bacillus, Subgroup 6 uncultured Acidobacteria, Candidatus Omnitrophica, and uncultured Nitrosomonadaceae. Presence of several potential nitrogen cycling bacteria (e.g., Nitrospira) in the study pools suggests that nitrogen cycling may be an important bacterial role. There is some evidence of human contamination, particularly in the heavily visited Big Room, Carlsbad Cavern, but it is not the dominant control. Rather than a single stable cave pool community, adapted to the cave pool ecosystem, the data show 17 different communities, despite relatively similar conditions. The data support the hypothesis that each pool is a unique, isolated ecosystem, with differences likely caused more by the isolation of each pool than by variable chemistry. Thus, the common habit of grouping samples, while useful for some questions, may not capture the diversity present in cave ecosystems.

DarkCideS 1.0, a global database for bats in karsts and caves

Understanding biodiversity patterns as well as drivers of population declines, and range losses provides crucial baselines for monitoring and conservation. However, the information needed to evaluate such trends remains unstandardised and sparsely available for many taxonomic groups and habitats, including the cave-dwelling bats and cave ecosystems. Here, we present the DarkCideS 1.0, a global database of bat caves and bat species based on curated data from the literature, personal collections, and existing datasets. The database contains information for geographical distribution, ecological status, species traits, and parasites and hyperparasites for 679 bat species known to occur in caves or use caves in their life-histories. The database contains 6746 georeferenced occurrences for 402 cave-dwelling bat species from 2002 cave sites in 46 countries and 12 terrestrial biomes. The database has been developed to be a collaborative, open-access, and user-friendly platform, allowing continuous data-sharing among the community of bat researchers and conservation biologists. The database has a range of potential applications in bat research and enables comparative monitoring and prioritisation for conservation.

Extremophile at a Glance: Ostracod Crustacean From a Chemoautotrophic Sulphidic Cave Ecosystem

Sulphidic cave ecosystems are remarkable evolutionary hotspots that have witnessed adaptive radiation of their fauna represented by extremophile species having particular traits. Ostracods, a very old group of crustaceans, exhibit specific morphological and ecophysiological features that enable them to thrive in groundwater sulphidic environments. Herein, we report a peculiar new ostracod species Pseudocandona movilaensis sp. nov. thriving in the chemoautotrophic sulphidic groundwater ecosystem of Movile Cave (Romania). The new species displays a set of homoplastic features specific for unrelated stygobitic species, for e.g., triangular carapace in lateral view with reduced postero–dorsal part and simplification of limb chaetotaxy (i.e., loss of some claws and reduction of secondary male sex characteristics), driven by a convergent or parallel evolution during or after colonization of the groundwater realm. P. movilaensis sp. nov. thrives exclusively in sulphidic meso-thermal waters (21°C) with high concentrations of sulphides, methane, and ammonium. Based on the geometric morphometrics-based study of the carapace shape and molecular phylogenetic analyses based on the COI marker (mtDNA), we discuss the phylogenetic relationship and evolutionary implication for the new species to thrive in groundwater sulphidic groundwater environments.

Developing global vulnerabilities and conservation priorities for cave-dwelling bats

Research and conservation interventions are disproportionately focused on taxa perceived as charismatic, while other systems with high levels of endemism, and often under-protected such as caves and subterranean ecosystems remain neglected. Bats are keystone to cave ecosystems making them ideal surrogates to understand diversity patterns and assay conservation priorities. Using a novel framework, we assessed and mapped the global bat cave vulnerabilities and priorities at the biome and site level. Almost half (N = 678, 48%) of bat species across the world regularly use caves, with 32% endemic to a single country, and 15% currently threatened with extinction. Tropical realms and small-ranged species faced the highest levels of risk. Our analyses consistently showed that most caves with lower threat levels show higher cave biotic potential (i.e., evolutionary distinctiveness and endemism), though this may be due to the loss of species from more disturbed caves. We estimate that 3% to 28% are high-priority caves for conservation in broad-scale (biome level) and fine-scale (site-dependent) analyses respectively. Amongst regions, the highest concentration of conservation priority areas are in the Palearctic and tropical regions (except Afrotropical), which requires more intensive data sampling. Our results further highlight the importance of prioritising bat caves at local scales but show that broader scale analysis is possible if robust cave data is present and effective parameters are included (i.e., appropriate landscape features and threats). Developing priorities for these systems requires more systematic approaches as a standard measure to develop the priorities needed to maintain cave diversity.

A Primer on Spider Assemblages in Levantine Caves: The Neglected Subterranean Habitats of the Levant—A Biodiversity Mine

Caves share unique conditions that have led to convergent adaptations of cave-dwelling animals. In addition, local factors act as filters on regional species-pools to shape the assemblage composition of local caves. Surveys of 35 Levantine caves, distributed along a climate gradient from the mesic in the north of Israel to hyper-arid areas in the south of Israel, were conducted to test the effect of cave characteristics, location, climate, bat presence, and guano level on the spider assemblage. We found 62 spider species and assigned four species as troglobites, 28 as troglophiles, and 30 as accidentals. Precipitation, elevation, latitude, minimum temperature, and guano levels significantly affected the composition of cave-dwelling spider assemblages. Caves situated in the Mediterranean region had higher species richness and abundance, as well as more troglobite and troglophile arachnids. These discoveries contribute to the knowledge of the local arachnofauna and are important for the conservation of cave ecosystems. By comparing spider assemblages of Levantine caves to European caves, we identified gaps in the taxonomic research, focusing our efforts on spider families that may have additional cryptic or yet to be described cave-dwelling spider species. Our faunistic surveys are crucial stages for understanding the evolutionary and ecological mechanisms of arachnid speciation in Levantine caves.

Integrative taxonomy uncovers a new stygobiotic Caridina species (Decapoda, Caridea, Atyidae) from Guizhou Province, China

Collecting much-needed information on the taxonomy, distribution, and ecology of cave-dwelling shrimp is vital for addressing the urgent challenges in conservation biodiversity in fragile cave ecosystems. Caridina incolorsp. nov., a new atyid shrimp from an underground stream of Yaoshui Cave, Daqikong scenic area, Libo County, Guizhou Province, southwestern China is described based on morphology and DNA analysis (mitochondrial COI). Caridina incolorsp. nov. differs from epigean congeners by its smaller eyes which range from reduced to completely blind; colorless body and appendages; long stylocerite and sixth abdominal segment; and relatively large eggs. In comparison to other cave species, Caridina incolorsp. nov. presents a long rostrum and stylocerite; slender sixth abdominal segment; and unique shape of the appendix masculina. Data on the habitat, ecology, and levels of threat are provided and suggest that it should be categorized as Critically Endangered (CR) under the current IUCN criteria.

Applying the Values of Geoethics for Sustainable Speleotourism Development

<p>Establishing sustainable and responsible speleotourism development is a major challenge and involves complex activities. Adequate theoretical starting point is the application of geoethical values related to the conservation and protection of the caves to be used for touristic purposes. Positive and negative cases of human behaviors towards speleological geoheritage are discussed, in order to highlight what should be done in cave management to avoid malpractices and on what elements could be founded adequate strategies aimed at promoting sustainable speleotourism. This is important to tourism management organizations involved in the promotion of caves and in creating economic opportunities for local populations, while respecting cave ecosystems. Modern cave management must be focused on the protection of the cave ecosystems, finding ways to achieve at the same time an economic development of local communities. But this approach needs the adoption of a geoethical framework of values to be shared by all stakeholders involved so that successful cooperation can be achieved despite differences in interests and expectations. The aim of this paper is to raise the awareness about the need to apply the values of geoethics to speleotourism, stimulating new fields of discussion within the scientific and technical communities involved in studies and activities related to geotourism and geoheritage. The possibilities of developing new ways to manage caves, in order to promote a sustainable socio-economic development of local communities, have to be balanced with the protection of natural environments as much as possible. The proposed theoretical frameworks have the goal to increase the discussion on the best ways of connecting speleotourism to sustainable and responsible cave management, presenting two case studies, and pointing out potential solutions.</p>

Bacteria and Metabolic Potential in Karst Caves Revealed by Intensive Bacterial Cultivation and Genome Assembly

ABSTRACT Karst caves are widely distributed subsurface systems, and the microbiomes therein are proposed to be the driving force for cave evolution and biogeochemical cycling. In past years, culture-independent studies on the microbiomes of cave systems have been conducted, yet intensive microbial cultivation is still needed to validate the sequence-derived hypothesis and to disclose the microbial functions in cave ecosystems. In this study, the microbiomes of two karst caves in Guizhou Province in southwest China were examined. A total of 3,562 bacterial strains were cultivated from rock, water, and sediment samples, and 329 species (including 14 newly described species) of 102 genera were found. We created a cave bacterial genome collection of 218 bacterial genomes from a karst cave microbiome through the extraction of 204 database-derived genomes and de novo sequencing of 14 new bacterial genomes. The cultivated genome collection obtained in this study and the metagenome data from previous studies were used to investigate the bacterial metabolism and potential involvement in the carbon, nitrogen, and sulfur biogeochemical cycles in the cave ecosystem. New N2-fixing Azospirillum and alkane-oxidizing Oleomonas species were documented in the karst cave microbiome. Two pcaIJ clusters of the β-ketoadipate pathway that were abundant in both the cultivated microbiomes and the metagenomic data were identified, and their representatives from the cultivated bacterial genomes were functionally demonstrated. This large-scale cultivation of a cave microbiome represents the most intensive collection of cave bacterial resources to date and provides valuable information and diverse microbial resources for future cave biogeochemical research. IMPORTANCE Karst caves are oligotrophic environments that are dark and humid and have a relatively stable annual temperature. The diversity of bacteria and their metabolisms are crucial for understanding the biogeochemical cycling in cave ecosystems. We integrated large-scale bacterial cultivation with metagenomic data mining to explore the compositions and metabolisms of the microbiomes in two karst cave systems. Our results reveal the presence of a highly diversified cave bacterial community, and 14 new bacterial species were described and their genomes sequenced. In this study, we obtained the most intensive collection of cultivated microbial resources from karst caves to date and predicted the various important routes for the biogeochemical cycling of elements in cave ecosystems.