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Speleology in Kazakhstan

Shakalov on 04 Jul, 2018
Hello everyone!   I pleased to invite you to the official site of Central Asian Karstic-Speleological commission ("Kaspeko")   There, we regularly publish reports about our expeditions, articles and reports on speleotopics, lecture course for instructors, photos etc. ...

New publications on hypogene speleogenesis

Klimchouk on 26 Mar, 2012
Dear Colleagues, This is to draw your attention to several recent publications added to KarstBase, relevant to hypogenic karst/speleogenesis: Corrosion of limestone tablets in sulfidic ground-water: measurements and speleogenetic implications Galdenzi,

The deepest terrestrial animal

Klimchouk on 23 Feb, 2012
A recent publication of Spanish researchers describes the biology of Krubera Cave, including the deepest terrestrial animal ever found: Jordana, Rafael; Baquero, Enrique; Reboleira, Sofía and Sendra, Alberto. ...

Caves - landscapes without light

akop on 05 Feb, 2012
Exhibition dedicated to caves is taking place in the Vienna Natural History Museum   The exhibition at the Natural History Museum presents the surprising variety of caves and cave formations such as stalactites and various crystals. ...

Did you know?

That moor is a wet peat bog [16].?

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Featured articles from Cave & Karst Science Journals
Chemistry and Karst, White, William B.
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Featured articles from other Geoscience Journals
Karst environment, Culver D.C.
Mushroom Speleothems: Stromatolites That Formed in the Absence of Phototrophs, Bontognali, Tomaso R.R.; D’Angeli Ilenia M.; Tisato, Nicola; Vasconcelos, Crisogono; Bernasconi, Stefano M.; Gonzales, Esteban R. G.; De Waele, Jo
Calculating flux to predict future cave radon concentrations, Rowberry, Matt; Marti, Xavi; Frontera, Carlos; Van De Wiel, Marco; Briestensky, Milos
Microbial mediation of complex subterranean mineral structures, Tirato, Nicola; Torriano, Stefano F.F;, Monteux, Sylvain; Sauro, Francesco; De Waele, Jo; Lavagna, Maria Luisa; D’Angeli, Ilenia Maria; Chailloux, Daniel; Renda, Michel; Eglinton, Timothy I.; Bontognali, Tomaso Renzo Rezio
Evidence of a plate-wide tectonic pressure pulse provided by extensometric monitoring in the Balkan Mountains (Bulgaria), Briestensky, Milos; Rowberry, Matt; Stemberk, Josef; Stefanov, Petar; Vozar, Jozef; Sebela, Stanka; Petro, Lubomir; Bella, Pavel; Gaal, Ludovit; Ormukov, Cholponbek;
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Your search for oxidizing bacteria (Keyword) returned 16 results for the whole karstbase:
Showing 1 to 15 of 16
THE OCCURRENCE AND EFFECT OF SULFATE REDUCTION AND SULFIDE OXIDATION ON COASTAL LIMESTONE DISSOLUTION IN YUCATAN CENOTES, 1993, Stoessell R. K. , Moore Y. H. , Coke J. G. ,
Dissolution of carbonate minerals in the coastal halocline is taking place in the karst terrain along the northeastern coast of the Yucatan Peninsula. The dissolution is being accelerated in cenotes (sinkholes) where sulfate reduction and oxidation of the produced sulfide is occurring. Hydrogen-sulfide concentrations ranged from 0.06 to 4 mmolal within the halocline in two sinkholes. Relative to concentrations expected by conservative mixing, fluids with high hydrogen-sulfide concentrations were correlated with low sulfate concentrations, high alkalinities, low pH values, and heavy sulfur isotope values for sulfate. Hydrogen-sulfide concentrations were less than those predicted from sulfate reduction, calculated from deficiencies in measured sulfate concentrations, indicating mobility and loss of aqueous sulfide. Fluids with low hydrogen-sulfide concentrations were correlated with very high calcium concentrations, high strontium and sulfate concentrations, slightly elevated alkalinities, low pH values, and sea-water sulfur isotope values for sulfate. Gypsum dissolution is supported by the sulfur isotopes as the major process producing high sulfate concentrations. However, oxidation of aqueous sulfide to sulfuric acid, resulting in carbonate-mineral dissolution is needed to explain the calcium concentrations, low pH values, and only slightly elevated alkalinities. The halocline may trap hydrogen sulfide that has been stripped from the underlying anoxic salt water. The halocline can act as a stable, physical boundary, holding some of the hydrogen sulfide until it is oxidized back to sulfuric acid through interaction with the overlying, oxygenated fresh water or through the activity of sulfide-oxidizing bacteria

Evidence for Geomicrobiological Interactions in Guadalupe Caves, 2000, Northup, D. E. , Dahm, C. N. , Melim, L. A. , Spilde, M. N. , Crossey, L. J. , Lavoie, K. H. , Mallory, L. M. , Boston, P. J. , Cummingham, K. I. , Barns, S. M.
Caves in the Guadalupe Mountains offer intriguing examples of possible past or present geomicrobiological interactions within features such as corrosion residues, pool fingers, webulites, u-loops, and moonmilk. Scanning electron microscopy, transmission electron microscopy, molecular biology techniques, enrichment cultures, bulk chemistry, and X-ray diffraction techniques have revealed the presence of iron- and manganese-oxidizing bacteria in corrosion residues, which supports the hypothesis that these organisms utilize reduced iron and manganese from the limestone, leaving behind oxidized iron and manganese. Metabolically active populations of bacteria are also found in punk rock beneath the corrosion residues. Microscopic examination of pool fingers demonstrates that microorganisms can be inadvertently caught and buried in pool fingers, or can be more active participants in their formation. Enrichment cultures of moonmilk demonstrate the presence of a variety of microorganisms. Humans can have a deleterious impact on microbial communities in Guadalupe caves

Acidic cave-wall biofilms located in the Frasassi Gorge, Italy, 2000, Vlasceanu L. , Sarbu S. M. , Engel A. S. , Kinkle B. K. ,
Acidic bioflms present on cave walls in the sulfidic region of the Frasassi Gorge, Italy, were investigated to determine their microbial composition and their potential role in cave formation and ecosystem functioning. All biofilm samples examined had pH values <1.0. Scanning electron microscopy of the biofilms revealed the presence of various filaments and rods associated in large clusters with mineral crystals. Qualitative energy-dispersive x-ray analysis was used to determine that the crystals present on the cave walls, associated with the microbial biofilm, were composed of calcium and barium sulfate. Ribosomal RNA-based methods to determine the microbial composition of these biofilms revealed the presence of at least two strains of potential acidophilic, sulfur-oxidizing bacteria, belonging to the genera Thiobacillus and Sulfobacillus. An acid producing strain of Thiobacillus sp. also was obtained in pure culture. Stable isotope ratio analysis of carbon and nitrogen showed that the wall biofilms are isotopically light, suggesting that in situ chemoautotrophic activity plays an important role in this subsurface ecosystem

Geomicrobiology of caves: A review, 2001, Northup D. E. , Lavoie K. H. ,
In this article, we provide a review of geomicrobiological interactions in caves, which are nutrient-limited environments containing a variety of redox interfaces. Interactions of cave microorganisms and mineral environments lead to the dissolution of, or precipitation on, host rock and speleothems (secondary mineral formations). Metabolic processes of sulfur-, iron-, and manganese-oxidizing bacteria can generate considerable acidity, dissolving cave walls and formations. Examples of possible microbially influenced corrosion include corrosion residues (e.g., Lechuguilla and Spider caves, New Mexico, USA), moonmilk from a number of caves (e.g., Spider Cave, New Mexico, and caves in the Italian Alps), and sulfuric acid speleogenesis and cave enlargement (e.g., Movile Cave, Romania, and Cueva de Villa Luz, Mexico). Precipitation processes in caves, as in surface environments, occur through active or passive processes. In caves, microbially induced mineralization is documented in the formation of carbonates, moonmilk, silicates, clays, iron and manganese oxides, sulfur, and saltpeter at scales ranging from the microscopic to landscape biokarst. Suggestions for future research are given to encourage a move from descriptive, qualitative studies to more experimental studies

Iron oxide-rich filaments: Possible fossil bacteria in Lechuguilla Cave, New Mexico, 2001, Provencio P. P. , Polyak V. J. ,
Reddish filaments in two fragments of unusual iron oxide bearing stalactites, 'the Rusticles' from Lechuguilla Cave, New Mexico, are found only within the central canals of the Rusticles. The curved, helical, and/or vibrioidal filaments vary from 1 to 6 mum in outer diameter and 10 to >50 mum in length. SEM and TEM show the filaments have 0.5-mum diameter central tubes, with goethite crystals radiating outwardly along their lengths. The diameter of the central tubes is consistent with the diameter of many iron-oxidizing filamentous bacteria. Although most iron oxide depositing bacteria do not deposit well-crystallized radiating goethite, we propose thick hydrous iron oxide was slowly crystallized from amorphous material to goethite, in place, over a relatively long period of time. From the gross morphology and the particular setting, we suggest this represents an occurrence of fossilized, acidophilic iron-oxidizing bacteria

Diverse microbial communities inhabiting ferromanganese deposits in Lechuguilla and Spider Caves, 2003, Northup D. E. , Barns S. M. , Yu L. E. , Spilde M. N. , Schelble R. T. , Dano K. E. , Crossey L. J. , Connolly C. A. , Boston P. J. , Natvig D. O. , Dahm C. N. ,
Lechuguilla Cave is an ancient, deep, oligotrophic subterranean environment that contains an abundance of low-density ferromanganese deposits, the origin of which is uncertain. To assess the possibility that biotic factors may be involved in the production of these deposits and to investigate the nature of the microbial community in these materials, we carried out culture-independent, small subunit ribosomal RNA (SSU rRNA) sequence-based studies from two sites and from manganese and iron enrichment cultures inoculated with ferromanganese deposits from Lechuguilla and Spider Caves. Sequence analysis showed the presence of some organisms whose closest relatives are known iron- and manganese-oxidizing/reducing bacteria, including Hyphomicrobium, Pedomicrobium, Leptospirillum, Stenotrophomonas and Pantoea. The dominant clone types in one site grouped with mesophilic Archaea in both the Crenarchaeota and Euryarchaeota. The second site was dominated almost entirely by lactobacilli. Other clone sequences were most closely related to those of nitrite-oxidizing bacteria, nitrogen-fixing bacteria, actinomycetes and beta- and gamma-Proteobacteria. Geochemical analyses showed a fourfold enrichment of oxidized iron and manganese from bedrock to darkest ferromanganese deposits. These data support our hypothesis that microorganisms may contribute to the formation of manganese and iron oxide-rich deposits and a diverse microbial community is present in these unusual secondary mineral formations

Bacterial diversity and ecosystem function of filamentous microbial mats from aphotic (cave) sulfidic springs dominated by chemolithoautotrophic 'Epsilonproteobacteria', 2004, Engel As, Porter Ml, Stern La, Quinlan S, Bennett Pc,
Filamentous microbial mats from three aphotic sulfidic springs in Lower Kane Cave. Wyoming. were assessed with regard to bacterial diversity, community structure, and ecosystem function using a 16S rDNA-based phylogenetic approach combined with elemental content and stable carbon isotope ratio analyses. The most prevalent mat morphotype consisted of while filament bundles, with low C:N ratios (3.5-5.4) and high sulfur content (16.1-51.2%). White filament bundles and two other mat morphotypes organic carbon isotope values (mean delta(13)C = -34.7parts per thousand: 1sigma = 3.6) consistent with chemolithoautotrophic carbon fixation from a dissolved inorganic carbon reservoir (cave water, mean delta(13)C = -7.47parts per thousand for two springs, n = 8). Bacterial diversity was as low overall in the clone libraries, and the most abundant taxonomic group was affiliated with the 'Epsilonproteobacteria' (68%) with other bacterial sequences affiliated with Gammaproteobacteria (12.2%), Betaproteobacteria (11.7%), Deltaproteobacteria (0.8%), and the Acidobacterium (5.6%) and Bacteriodetes/Chlorobi (1.7%) divisions. Six distinct epsilonproteobacterial taxonomic groups were identified from the microbial mats. Epsilonproteobacterial and bacterial group abundances and community structure shifted front the spring orifices downstream. corresponding to changes in dissolved sulfide and oxygen concentrations and metabolic requirements of certain bacterial groups. Most of the clone sequences for epsilonproteobacterial groups were retrieved from areas with high sulfide and low oxygen concentrations, whereas Thiothrix spp. and Thiobacillus spp. had higher retrieved clone abundances where conditions of low sulfide and high oxygen concentrations were measured. Genetic and metabolic diversity among the 'Epsilonproteobacteria' maximizes overall cave ecosystem function, and these organisms play a significant role in providing chemolithoautotrophic energy to the otherwise nutrient-poor cave habitat. Our results demonstrate that sulfur cycling supports subsurface ecosystem through chemolithoautotrophy and expand the evolutionary and ecological views of 'Epsilonproteobacteria' in terrestrial habitats. (C) 2004 Federation of European Microbiological Societies. Published by Elsevier BY. All rights reserved

Microbial contributions to cave formation: New insights into sulfuric acid speleogenesis, 2004, Engel As, Stern La, Bennett Pc,
The sulfuric acid speleogenesis (SAS) model was introduced in the early 1970s from observations of Lower Kane Cave, Wyoming, and was proposed as a cave-enlargement process due to primarily H2S autoxidation to sulfuric acid and subaerial replacement of carbonate by gypsum. Here we present a reexamination of the SAS type locality in which we make use of uniquely applied geochemical and microbiological methods. Little H2S escapes to the cave atmosphere, or is lost by abiotic autoxidation, and instead the primary H2S loss mechanism is by subaqueous sulfur-oxidizing bacterial communities that consume H2S. Filamentous 'Epsilonproteobacteria' and Gammaproteobacteria, characterized by fluorescence in situ hybridization, colonize carbonate surfaces and generate sulfuric acid as a metabolic byproduct. The bacteria focus carbonate dissolution by locally depressing pH, compared to bulk cave waters near equilibrium or slightly supersaturated with calcite. These findings show that SAS occurs in subaqueous environments and potentially at much greater phreatic depths in carbonate aquifers, thereby offering new insights into the microbial roles in subsurface karstification

Geomicrobiology of cave ferromanganese deposits: A field and laboratory investigation, 2005, Spilde M. N. , Northup D. E. , Boston P. J. , Schelble R. T. , Dano K. E. , Crossey L. J. , Dahm C. N. ,
Unusual ferromanganese deposits are found in several caves in New Mexico. The deposits are enriched in iron and manganese by as much as three orders of magnitude over the bedrock, differing significantly in mineralogy and chemistry from bedrock-derived insoluble residue. The deposits contain metabolically active microbial communities. Enrichment cultures inoculated from the ferromanganese deposits produced manganese oxides that were initially amorphous but developed into crystalline minerals over an 8-month period and beyond; no such progression occurred in killed controls. Phylogenetic analyses of sequences from clone libraries constructed from culture DNA identified two genera known to oxidize manganese, but most clones represent previously unknown manganese oxidizers. We suggest that this community is breaking down the bedrock and accumulating iron and manganese oxides in an oligotrophic environment

Geomicrobiology of biovermiculations from the Frasassi Cave System, Italy, 2008, D. S. Jones, E. H. Lyon, And J. L. Macalady

Sulfidic cave walls host abundant, rapidly-growing microbial communities that display a variety of morphologies previously described for vermiculations. Here we present molecular, microscopic, isotopic, and geochemical data describing the geomicrobiology of these biovermiculations from the Frasassi cave system, Italy. The biovermiculations are composed of densely packed prokaryotic and fungal cells in a mineral-organic matrix containing 5 to 25% organic carbon. The carbon and nitrogen isotope compositions of the biovermiculations (d13C 5 235 to 243%, and d15N 5 4 to 227%, respectively) indicate that within sulfidic zones, the organic matter originates from chemolithotrophic bacterial primary productivity. Based on 16S rRNA gene cloning (n567), the biovermiculation community is extremely diverse, including 48 representative phylotypes (.98% identity) from at least 15 major bacterial lineages. Important lineages include the Betaproteobacteria (19.5% of clones), Gammaproteobacteria (18%), Acidobacteria (10.5%), Nitrospirae (7.5%), and Planctomyces (7.5%). The most abundant phylotype, comprising over 10% of the 16S rRNA gene sequences, groups in an unnamed clade within the Gammaproteobacteria. Based on phylogenetic analysis, we have identified potential sulfur- and nitrite-oxidizing bacteria, as well as both auto- and heterotrophic members of the biovermiculation community. Additionally, many of the clones are representatives of deeply branching bacterial lineages with no cultivated representatives. The geochemistry and microbial composition of the biovermiculations suggest that they play a role in acid production and carbonate dissolution, thereby contributing to cave formation.


Niche differentiation among sulfur-oxidizing bacterial populations in cave waters, 2008, Jennifer L Macalady, Sharmishtha Dattagupta, Irene Schaperdoth, Daniel S Jones, Greg K Druschel And Danielle Eastman
The sulfidic Frasassi cave system affords a unique opportunity to investigate niche relationships among sulfur-oxidizing bacteria, including epsilonproteobacterial clades with no cultivated representatives. Oxygen and sulfide concentrations in the cave waters range over more than two orders of magnitude as a result of seasonally and spatially variable dilution of the sulfidic groundwater. A full-cycle rRNA approach was used to quantify dominant populations in biofilms collected in both diluted and undiluted zones. Sulfide concentration profiles within biofilms were obtained in situ using microelectrode voltammetry. Populations in rock-attached streamers depended on the sulfide/oxygen supply ratio of bulk water (r¼0.97; Po0.0001). Filamentous epsilonproteobacteria dominated at high sulfide to oxygen ratios (4150), whereas Thiothrix dominated at low ratios (o75). In contrast, Beggiatoa was the dominant group in biofilms at the sediment?water interface regardless of sulfide and oxygen concentrations or supply ratio. Our results highlight the versatility and ecological success of Beggiatoa in diffusion-controlled niches, and demonstrate that high sulfide/oxygen ratios in turbulent water are important for the growth of filamentous epsilonproteobacteria.

Spatial-dynamic peculiarities of CO2 distribution in the air of Zoloushka Cave, 2011, Andreychouk V. , Teleshman I. , Kouprich P.

Zoloushka Cave is characterized by relatively high (1-5%) content of 2 in its underground atmosphere. The source of 2 is the oxidation of organic matter and methane by ammonifying and methane-oxidizing bacteria. The accumulation of carbon dioxide in the cave air is caused by slow air exchange with the surface. The distribution of 2 through the cave space has been investigated in August 2008 and 2009 and compared with the CO2 distribution in 1982. The main regularities of 2 distribution in the cave are region-by-region increase in CO2 concentrations in the direction from the entrance into depth of cave and the vertical stratification – increase of carbon dioxide content in depressions of cave bottom and shafts. The influence of 2 on the working conditions in the cave, on the human body and his mind, is also analyzed. The integral table of safety precautions is proposed, which should be followed when doing of research in the cave


Iron Oxide and Calcite Associated with Leptothrix sp. Biofilms within an Estavelle in the Upper Floridan Aquifer, 2011, Florea Lee J. , Stinson Chasity L. , Brewer Josh, Fowler Rick, Kearns B Joe, Greco Anthony M.

In Thornton’s Cave, an estavelle in west-central Florida, SEM, EDS, and XRD data reveal biofilms that are predominantly comprised of FeOOH-encrusted hollow sheaths that are overgrown and intercalated with calcite. Fragments of this crystalline biofilm adhere to the walls and ceiling as water levels vary within the cave. Those on the wall have a ‘cornflake’ appearance and those affixed to the ceiling hang as fibrous membranes. PCR of DNA in the active biofilm, combined with morphologic data from the tubes in SEM micrographs, point to Leptothrix sp., a common Fe-oxidizing bacteria, as the primary organism in the biofilm. Recent discoveries of ‘rusticles’ in other Florida caves suggest that Fe-oxidizing bacteria may reside elsewhere in Florida groundwater and may play a role in the mobility of trace metals in the Upper Florida aquifer.
SEM micrographs from two marble tablets submerged for five months, one exposed to microbial activity and a second isolated from microbial action, revealed no visible etchings or borings and very limited loss of mass. EDS data from the electron micrographs of the unfiltered tablet document the same FeOOH-encrusted hollow sheaths and similar deposits of calcite as seen in the ‘cornflakes’. These results, combined with water chemistry data imply that the biofilm may focus or even promote calcite precipitation during low-water level conditions when CO2 degasses from the cave pools.


Aqueous Geochemical Evidence of Volcanogenic Karstification: Sistema Zacaton, Mexico, 2011, Gary M. O. , Doctor D. H. , Sharp J. M.

The Sistema Zacatón karst area in northeastern Mexico (Tamaulipas state) is limited to a relatively focused area (20 km2) in a carbonate setting not prone to extensive karstification. The unique features found here are characteristic of hydrothermal karstification processes, represent some of the largest phreatic voids in the world, and are hypothesized to have formed from interaction of a local Pleistocene magmatic event with the regional groundwater system. Aqueous geochemical data collected from five cenotes of Sistema Zacatón between 2000 and 2009 include temperature (spatial, temporal, and depth profiles), geochemical depth profiles, major and trace ion geochemistry, stable and radiogenic isotopes, and dissolved gases. Interpretation of these data indicates four major discoveries: 1) rock-water interaction occurs between groundwater, the limestone matrix, and local volcanic rocks; 2) varying degrees of hydrogeological connection exist among cenotes in the system as observed from geochemical signatures; 3) microbially-mediated geochemical reactions control sulfur and carbon cycling and influence redox geochemistry; and 4) dissolved gases are indicative of a deep volcanic source. Dissolved 87Sr/86Sr isotope ratios (mean 0.70719) are lower than those of the surrounding Cretaceous limestone (0.70730-0.70745), providing evidence of groundwater interaction with volcanic rock, which has a 87Sr/86Sr isotope ratio of 0.7050. Discrete hydraulic barriers between cenotes formed in response to sinkhole formation, hydrothermal travertine precipitation, and shifts in the local water table, creating relatively isolated water bodies. The isolation of the cenotes is reflected in distinct water chemistries among them. This is observed most clearly in the cenote Verde where a water level 4-5 meters lower than the adjacent cenotes is maintained, seasonal water temperature variations occur, thermoclines and chemoclines exist, and the water is oxic at all depths. The surrounding cenotes of El Zacatón, Caracol, and La Pilita show constant water temperatures both in depth profile and in time, have similar water levels, and are almost entirely anoxic. A sulfur (H2S) isotope value of δ34S = -1.8 ‰ (CDT) in deep water of cenote Caracol, contrasted with two lower sulfur isotopic values of sulfide in the water near the surface of the cenote (δ34S = -7 ‰ and -8 ‰ CDT). These δ34S values are characteristic of complex biological sulfur cycling where sulfur oxidation in the photic zone results in oxidation of H2S to colloidal sulfur near the surface in diurnal cycles. This is hypothesized to result from changes in microbial community structure with depth as phototropic, sulfur-oxidizing bacteria become less abundant below 20 m. Unique microbial communities exist in the anoxic, hydrothermal cenotes that strongly mediate sulfur cycling and likely influence mineralization along the walls of these cenotes. Dissolved CO2 gas concentrations ranged from 61-173 mg/L and total dissolved inorganic carbon (DIC) δ13C values measured at cenote surfaces ranged from -10.9 ‰ to -11.8 ‰ (PDB), reflecting mixed sources of carbon from carbonate rock dissolution, biogenic CO2 and possibly dissolved CO2 from volcanic sources. Surface measurements of dissolved helium gas concentrations range from 50 nmol/kg to 213 nmol/kg. These elevated helium concentrations likely indicate existence of a subsurface volcanic source; however, helium isotope data are needed to test this hypothesis. The results of these data reflect a speleogenetic history that is inherently linked to volcanic activity, and support the hypothesis that the extreme karst development of Sistema Zacatón would likely not have progressed without groundwater interaction with the local igneous rocks 


Ostracod Assemblages in the Frasassi Caves and Adjacent Sulfidic Spring and Sentino River in the Northeastern Apennines of Italy, 2013, Peterson D. E. , Finger K. L. , Iepure S. , Mariani S. , Montanari A. , Namiotko T.

Rich, diverse assemblages comprising a total (live + dead) of twenty-one ostracod species belonging to fifteen genera were recovered from phreatic waters of the hypogenic Frasassi Cave system and the adjacent Frasassi sulfidic spring and Sentino River in the Marche region of the northeastern Apennines of Italy. Specimens were recovered from ten sites, eight of which were in the phreatic waters of the cave system and sampled at different times of the year over a period of five years. Approximately 6900 specimens were recovered, the vast majority of which were disarticulated valves; live ostracods were also collected. The most abundant species in the sulfidic spring and Sentino River were Prionocypris zenkeri, Herpetocypris chevreuxi, and Cypridopsis vidua, while the phreatic waters of the cave system were dominated by two putatively new stygobitic species of Mixtacandona and Pseudolimnocythere and a species that was also abundant in the sulfidic spring, Fabaeformiscandona ex gr. F. fabaeformis.
Pseudocandona ex gr. P. eremita, likely another new stygobitic species, is recorded for
the first time in Italy. The relatively high diversity of the ostracod assemblages at Frasassi
could be attributed to the heterogeneity of groundwater and associated habitats or to
niche partitioning promoted by the creation of a chemoautotrophic ecosystem based on
sulfur-oxidizing bacteria. Other possible factors are the geologic age and hydrologic
conditions of the cave and karst aquifer system that possibly originated in the early–
middle Pleistocene when topographic uplift and incision enabled deep sulfidic waters to
reach the local carbonate aquifer. Flooding or active migration would have introduced
the invertebrates that now inhabit the Frasassi Cave system


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