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Enviroscan Ukrainian Institute of Speleology and Karstology

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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 fountain is a free-flowing well or spring [16]. see also artesian well; spring, artesian.?

Checkout all 2699 terms in the KarstBase Glossary of Karst and Cave Terms

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Browse Speleogenesis Issues:

KarstBase a bibliography database in karst and cave science.

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 reaches (Keyword) returned 101 results for the whole karstbase:
Showing 91 to 101 of 101
A high-resolution spatial survey of cave air carbon dioxide concentrations in Scoska Cave (North Yorkshire, UK): implications for calcite deposition and re-dissolution, 2010,
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Whitaker, Tom, Daniel Jones, James U L Baldini And Alex J Baker
Carbon dioxide concentration variability in caves has implications for palaeoclimatic research involving stalagmites, the conservation of cave art, condensation corrosion, and safety during cave exploration. Here we present a high-resolution spatial survey of cave air carbon dioxide partial pressure (PCO2) in the 1.5km Scoska Cave system in North Yorkshire, UK, constructed using measurements taken during the interval of July 1 to July 5, 2008. According to the spatial P-CO2 survey, 76% of the cave air P-CO2 increase occurred within the first ~50 metres; consequently the P-CO2 gradient throughout the rest of the cave was slight. As is the case in other caves, this suggests that a 'front' exists at this site between high P-CO2 cave air and low P-CO2 outside air, where the P-CO2 increases dramatically over a short distance. Temperature data support this interpretation. This CO2 'front' is thought to represent the farthest point reached by large-scale advection of air out of the cave, and its position is hypothesized to fluctuate depending on atmospheric conditions. Thus, distinct P-CO2 trends characterize sections of the Scoska Cave system, which result in spatial variability in calcite deposition and redissolution. Modelled stalagmite growth rates vary between negligible and 0.21 mm yr-1, depending on unconstrained drip water [Ca2+] values and cave atmosphere P-CO2. Assuming constant drip water [Ca2+], optimum calcite deposition occurs near to the cave entrance, where ventilation and advection reduce P-CO2 levels most effectively. However, calcite precipitation on the roof of the cave may partially control the [Ca2+] of drip water that reaches the floor, so although the link between overall calcite deposition (i.e., on the roof and the floor) and P-CO2 appears robust, the effect of variable cave air P-CO2 on stalagmite growth rates requires more research. These calculations suggest that calcite precipitation rates in different areas of Scoska Cave may differ due to local P-CO2 and temperature variability, highlighting the benefits of thoroughly understanding site-specific cave environmental factors prior to the interpretation of stalagmite-based palaeoclimate records.

Catchment scale tracer testing from karstic features in a porous limestone, 2010,
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Maurice L. , Atkinson T. C. , Williams A. T. , Barker J. A. , Farrant A. R.

Tracer testing was undertaken from sinking streams feeding the Chalk, a porous limestone aquifer characterised by frequent small-scale surface karst features. The objective was to investigate the nature and extent of sub-surface karstic development in the aquifer. Previous tracer testing has demonstrated rapid flow combined with low attenuation of tracer. In this study, at two sites rapid groundwater flow was combined with very high attenuation and at two other sites no tracer was detected at springs within the likely catchment area of the stream sinks tested, suggesting that tracer was totally attenuated along the flowpath. It is proposed that the networks beneath stream sinks in the Chalk and other mildly karstic aquifers distribute recharge into multiple enlarged fractures that divide and become smaller at each division whereas the networks around springs have a predominantly tributary topology that concentrates flow into a few relatively large cavities, a morphology with similarities to that of the early stages of karstification. Tracer attenuation is controlled by the degree to which the two networks are directly connected. In the first state, there is no direct linkage and flow between the two networks is via primary fractures in which tracer attenuation is extreme. The second state is at a percolation threshold in which a single direct link joins the two networks. A very small proportion of tracer reaches the spring rapidly but overall attenuation is very high. In the third state, the recharge and discharge networks are integrated therefore a large fraction of tracer reaches the spring and peak concentrations are relatively high. Despite the large number of stream sinks that recharge the Chalk aquifer, these results suggest that sub-surface conduit development may not always be continuous, with flow down smaller fissures and fractures causing high attenuation of solutes and particulates providing a degree of protection to groundwater outlets that is not seen in more highly karstic aquifers. Bacteriophage tracers that can be detected at very large dilutions (1015) are recommended for investigating groundwater pathways where attenuation may be high.

Flash flood hydrology in karstic terrain: Flumineddu Canyon, central-east Sardinia, 2010,
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De Waele Jo, Martina Mario L. V. , Sanna Laura, Cabras Salvatore, Cossu Quirico Antonio

In the last five winters (2004–2008) several exceptional meteorological events producing flash floods have been registered in central-east Sardinia. The first of these (December 2004) was the most severe and caused important geomorphic changes in the Riu Flumineddu watershed where the influence of human activity is limited. The hydrological characterisation of this flood is extremely difficult because of the lack of streamflow gauges and the relative paucity of meteorological stations in the region. Peak discharge of the fluviokarstic Riu Flumineddu Canyon has been estimated based on a distributed hydrological model (TOPKAPI) and on empirical methods based on geomorphic and sedimentological observations. The comparison between the results derived from these independent methods allows us to obtain the best possible estimate of peak discharge. Differences between modelled and measured peak flows can be attributed to water losses and/or gains along the river channel from interactions with the underground karst drainage network.

The December 2004 flood, with an estimated recurrence interval of at least 65 years, generated overbank flow and destroyed several bridges in upstream reaches, caused important changes in channel morphology and sediment distribution and was able to move boulders up to 1 m in diameter in downstream reaches.

Landscape evolution in southeast Wales: evidence from aquifer geometry and surface topography associated with the Ogof Draenen cave system, 2011,
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Simms Michael J, Farrant Andrew R

The evolution of the Ogof Draenen cave system, in south-east Wales, has been profoundly influenced by the geometry of the karst aquifer and its relationship with changes in the surface topography. Using data from within the cave combined with a model of the aquifer geometry based on outcrop data, we have estimated the location and elevation of putative sinks and risings for the system by extrapolating from surveyed conduits in the cave. These data have enabled us to assess the scale and pattern of scarp retreat and valley incision in the valleys of the Usk, Clydach and Lwyd, that together have influenced the development of the cave. From this we can construct a relative chronology for cave development and landscape evolution in the region. Our data show that scarp retreat rates along the west flank of the Usk valley have varied by more than an order of magnitude, which we interpret as the result of locally enhanced erosion in glacial cirques repeatedly occupied and enlarged during successive glacial cycles. This process would have played a key role in breaching the aquiclude, created by the eastward overstep of the Marros Group clastics onto the Cwmyniscoy Mudstone, and thereby allowed the development of major conduits draining further south. In the tributary valleys incision rates were substantially greater in the Clydach valley than in the Lwyd valley, which we attribute to glacial erosion predominating in the north-east-facing Clydach valley and fluvial erosion being dominant in the south-facing Lwyd valley. There is evidence from within Ogof Draenen for a series of southward-draining conduits graded to a succession of palaeoresurgences, each with a vertical separation of 4-5 m, in the upper reaches of the Lwyd valley. We interpret these conduits as an underground proxy for a fluvial terrace staircase and suggest a direct link with glacial-interglacial cycles of surface aggradation and incision in the Lwyd valley. Fluvial incision rates for broadly analogous.

Geochemical evolution of groundwater in the unsaturated zone of a karstic massif, using the PCO2SIc relationship, 2012,
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Peyraube N. , Lastennet R. , Denis A.

In karstic environments, groundwater is strongly influenced by CO2 partial pressure variations of air present in the infiltration zone of these aquifers. In order to characterize the geochemical changes in groundwater as it moves through the infiltration zone, we monitored various rising springs in the perched karstic aquifer of Cussac (Dordogne, France), and measured the CO2 partial pressure in air of a nearby cavity (the Cussac Cave) for 24 months. Our method is based on the relationship between the saturation index with respect to calcite (SIc) and the CO2 partial pressure at atmospheric equilibrium with water. We distinguished a value for this last parameter when water is at equilibrium with respect to calcite (SIc = 0) called saturation CO2 partial pressure. The use of this parameter can provide information on flow conditions and relationships between water, air, and rock. Cussac aquifer is a suitable area to apply these methods because of its small size, numerous springs, and a cave that provides data for CO2 partial pressure condition inside the massif. Results show that most of the calcium-carbonate mineralization is acquired in the epikarst followed by a precipitation phase in the upper part of the infiltration zone. Groundwater reaches the saturated zone with some degree of saturation depending on CO2 partial pressure variations in air inside the massif.

Groundwater recharge and exploitative potential zone mapping using GIS and GOD techniques, 2012,
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Huang C. C. , Yeh H. F. , Lin H. I. , Lee S. T. , Hsu K. C. , Lee C. H.

Two-thirds of the total area of Taiwan is mountainous terrain, which is the main groundwater recharge source of the plains region. This study assesses groundwater recharge and exploitative potential zone in the central division of the mountain areas of Taiwan (the middle reaches of the Jhuoshuei River Basin). Basic information from remote sensing and a satellite phantom is collected to set up the basic data maps using elevation, Formosa-II images, the Normalized Difference Vegetation Index, drainage distribution, slope, aspect ratio, lineament distribution, and land cover. A geographical information system is used to integrate five contributing factors, namely lithology, land cover/land use, drainage, slope, and lineaments. The criteria for the recharge potential assessment are established to demarcate the potential groundwater recharge zone. Finally, the GOD rating system is adopted to evaluate the potential exploitation zone. Three main parameters are considered: the groundwater occurrence, the lithology of the overlying layers, and the depth to groundwater. The results show that the middle reaches of the Chenyuland River have large potential exploitation zones due to its high rainfall recharge capacity. Regions west of the Jhuoshuei River and the downstream regions of the Chingshui River are medium potential exploitation zones because of their high infiltration rates and shallow groundwater levels

Environmental Hydrogeological Study of Louros watershed, Epirus, Greece, 2012,
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Konstantina Katsanou

The present study aims to describe and characterize the Ionian zone karst formation concerning the karstification grade of carbonate formations and the development of aquifers, through the hydrogeological study of Louros River drainage basin, considering hydrological, hydrogeological and meteorological data, as well as major, trace element, rare earth element and isotope concentrations. It also aims to investigate basic karst properties such as storativity, homogeneity, infiltration coefficients and the parameters of the Louros basin hydrological balance.

To accomplish this aim daily discharge measurements obtained from Public Power Corporation at the Pantanassa station during the years 1956-1957, along with random discharge measurements from 15 springs along the basin performed by IGME between the years 1979-1989, daily meteorological data from 18 stations and 18 sets of potentiometric surface measurements from 38 sites were compiled. Additionally, chemical analyses on major and trace element concentrations of 42 rock samples and of five sets of water samples from 64 sampling sites, along with fourteen sets of successive periods in order to study the seasonal variation in the chemical composition of 11 springs and REE concentrations of 116 water samples. Moreover isotope ratios from 129 rain samples collected at five different altitudes, 331 samples of surface and groundwater samples, radon measurements on 21 groundwater samples and microbiological on 46 samples of surface and groundwater were evaluated. Daily runoff and random spring discharge missing data were completed applying the SAC-SMA and MODKARST simulation algorithms and the values of these parameters for the duration of the research (2008-2010) were predicted. The accuracy of the predicted values was tested applying statistical methods but also against observed values from in situ measurements performed during the same period (2008-2010).

Louros River drainage basin is located at the southern part of Epirus and covers an area of 953 km2. It is elongated and together with the adjacent basin of River Arachthos they constitute the major hydrographic systems discharging in the Amvrakikos Gulf. The main morphological features of the basin are elongated mountain ranges and narrow valleys, which are the result of tectonic and other geological processes mainly controlled by the limestone-“flysch” alternations. The length of the river’s major channel, which is parallel to the major folding direction (NNW-SSE), is 73.5 km. The mountainous part of the hydrogeological basin covers an area of 400 km2 and its endpoint was set at the Pantanassa station, where discharge measurements are performed. The underground limits of the basin coincides with the surface one, defined by the flysch outcrops at the western margin of the Ziros-Zalongo fault zone to the South, the application of isotope determinations and hydraulic load distribution maps at the North and East.

Geologically, Louros River drainage basin is composed of the Ionian zone formations. Triassic evaporites constitute the base of the zone overlain by a thick sequence of carbonate and clastic sedimentary rocks deposited from the Late Triassic to the Upper Eocene. In more detail, from base to top, the lithostratigraphical column of the zone includes dolomite and dolomitic limestone, Pantokrator limestone, Ammonitico Rosso, Posidonia Shales, Vigla limestone, Upper Senonian limestone, Palaeocene-Eocene limestone and Oligocene “flysch”. The major tectonic features of the regions are folds with their axes trending SW-NE at the northern part and NNW-SSE to NNE-SSW southern of the Mousiotitsa-Episkopiko-Petrovouni fault system and the strike-slip fault systems of Ziros and Petousi.

The evaluation of the daily meteorological data revealed that December is the most humid month of the year followed by January, whereas July and August are the driest months. Approximately 40-45% of the annual precipitation is distributed during the winter time and 30% during autumn. The mean annual precipitation ranges from 897.4 to 2051.8 mm and the precipitation altitude relationship suggests an increased precipitation with altitude at a rate of 84 mm/100 m. The maximum temperature is recorded during August and it may reach 40°C and the minimum during January. The temperature variation with the altitude is calculated at 0.61°C/100 m. The maximum solarity time is 377.8 h, recorded during July at the Arta station. December displays the highest relative humidity with a value of 84.2% recorded again at the Arta station. The highest wind velocity values are recorded at the Preveza station and similar velocities are also recorded at the Ioannina station. The real evapotranspiration in Louros drainage basin ranges between 27-39%. The potential evapotranspiration was calculated from the Ioannina station meteorological data, which are considered more representative for Louros basin, at 785.8 mm of precipitation according to Thornthwaite and at 722.0 mm according to Penman-Monteith.

According to the SAC-SMA algorithm the total discharge (surficial and underground) for the years 2008-2010 ranges between 61-73% of the total precipitation. The algorithm simulates the vertical percolation of rainwater in both unsaturated and saturated zones taking into account 15 parameters including the tension water capacity of the unsaturated zone, the maximum water storage capacity of both unsaturated and saturated zones, the water amount escaping into deeper horizons and not recorded at the basin’s outlet, the percentage of impermeable ground which is responsible for instant runoff, etc. These parameters are correlated to the hydrograph and are recalculated according to it. Two interesting aspects were pointed out from the discharge measurements and the algorithm application. The first is related to the maximum amount of free water, which can be stored at the basic flow of the karstic system, which is very high for the whole basin, reaching 1200 mm of precipitation and the second is the amount of water filtered to the deeper horizons, which reaches 0.098.

The discharge of individual karstic units was simulated applying the specialized MODKARST code. The code, which transforms precipitation to discharge resolving mathematical equations of non-linear flow using the mass and energy balance, successfully completed the time series of available data of spring discharge measurements for the period between the years 2008-2010.

Additionally, a number of useful parameters including spring recharge, delay period between precipitation and discharge, the storage capacity of the discharge area were also calculated by the MODKARST code. These data enabled the calculation of the annual infiltration coefficient for each one of the 15 springs and for the whole basin; the latter was found to range between 38-50% of annual precipitation. The total supply area was estimated approximately at 395 km2, which is consistent with the area of Louros hydrogeological basin calculated from hydrogeological data.

The 18 sets of water table measurements, each one corresponding to a different period, revealed that the aquifers of the intermediate part of Louros basin, which are developed in Quaternary alluvial sediments, are laterally connected to the carbonate formations of the individual karstic spring units, forming a common aquifer with a common water table.

Groundwater flow follows a general N-S direction from the topographic highs to the coastal area with local minor shifts to NE-SW and NW-SE directions. The artificial lake at the position of the Public Power Corporation’s Dam at the south of the region is directly connected to the aquifer and plays an important role in water-level variation. The water table contours display a higher gradient to the southern part due to the decreased hydraulic conductivity of the limestones close to Agios Georgios village. The decreased hydraulic conductivity is believed to be the reason for the development of the homonymous spring although the hydraulic load distributions suggest the extension of the aquifer to the south and a relation to the water level in Ziros Lake, boreholes and the Priala springs. The hydraulic gradient in the broader region ranges between 4-16‰. The absolute water level variation between dry and humid season ranges from 2 m at the South to 15-20 m to the North with an average of 9 m.

The hydrological balance of Louros River mountainous basin according to the aforementioned data is calculated as follows: The total precipitation between the years 2008-2010 ranged between 5.67E+08-9.8E+08 m3 and the discharge at Pantanassa site between 3.47E+08-6.83E+08 m3. The real evapotransiration ranged between 29-39% of the precipitation. The total discharge (runoff and groundwater) accounted for 61-73% of the precipitation, whereas the basic flow due to the percolation ranged between 34-38%. Considering a mean water level variation of 9 m, between the dry and humid season, the water amount constituting the local storage is 2025Ε+07 m3.

Statistical evaluation on spring discharge data and the recession curves analysis revealed three distinct levels with diverse karstic weathering along Louros basin coinciding to the upper, intermediate and low flow of Louros River, respectively. The developed karstic units are generally complex but simple individual units develop as well. The response of spring discharge to the stored water amounts is immediate but with relatively large duration suggesting the storage of large quantities of water and a well-developed system of karstic conduits, which however has not yet met its complete evolution. The karst spring’s units are homogeneous and each one is distinguished from different recession coefficients.

The three levels of flow are also distinguished from the duration curves, which point to individual units upstream, complex units receiving and transmitting water to the adjacent ones in the middle part and complex that only receive water from the upper. This distinguishment is also enhanced by the groundwater’s major ion concentrations, which reveal Ca-HCO3 water-type upstream, along with the isotopic composition at the same part. The prevalent Ca-HCO3-Cl-SO4 water-type in the middle part, the Na-Ca-Cl-SO4 water-type downstream and isotope variation confirms this distinguishment. Moreover, REE variation is also consistent with the three levels. The assumption of relatively large stored water reserves, which contribute to analogous “memory” of spring karstic units, as pointed out by autocorreletion functions is enhanced from SAC-SMA algorithm which premises an increased capacity at the lower zone of basic flow, as well as from the hydrochemical and isotopic composition of groundwater. Monitoring of the seasonal variation in groundwater composition revealed minor variations of hydrochemical parameters and remarkably stable isotopic composition. Both aspects can be explained by the existence of a considerable water body acting as a retarder to external changes.

The crosscorrelation functions suggest a well-developed karstic system, which however has not yet reached its complete maturity also confirmed from field observations. The same conclusion is extracted from the homogeneous evolution at the interval of each karstic unit as demonstrated from recession curves on spring hydrographs.

The results from hydrochemical analyses also revealed the effect of evaporitic minerals and phosphate-rich rocks in groundwater composition and confirmed the hydraulic relationships between surface and groundwater.

The study of the isotopic composition also contributed to exclude the potential connection between the Ioannina and Louros basins, confirmed the meteoric origin of groundwater and revealed the effect of seawater in the chemical composition of few sampling sites.

The microbiological research only revealed minor incidents of contamination and significant attenuation of microorganisms during periods of high discharge.

Karst hierarchical flow systems in the Western Cordillera of North America, 2013,
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Ford, Derek

By definition, karstic flow systems are networks of solutional conduits. Their spatial patterns and hierarchical organisation are strongly affected by differing lithology and geologic structure, and by the location and modes of recharge – unconfined, confined, interformational. For purposes of discussion, this paper will review six examples rang-ing across platform and reefal limestones and dolostones, dolostone breccias, gypsum and salt, in widely differing structural, geomorphic and hydrologic settings: (1) The Carcajou River karst at Lat. 65° N in the Mackenzie Mountains, where leaky permafrost superimposes a frozen ground hierarchy on those due to lithology, structure and topog-raphy: (2) The S Nahanni River karst at Lat. 62° N, with an intrusive-derived local thermal system and lengthy, strike-oriented meteoric flow systems that contribute to an outlet H2S thermal system at the basin topographic low: (3) Castleguard Mountain Karst (Lat. 52° N) in massive Main Ranges structures of the Rocky Mountains, with a complex alpine hierarchy of base-flow and overflow springs: (4) Crowsnest Pass, in steep thrust structures in the Rocky Mountain Front Ranges, where regional strike-oriented flow systems extending between Lats. 49° and 50° N and paired above and below a major aquitard have been disaggregated by glacial cirque incision: (5) The Black Hills geologic dome at Lat. 44° N in South Dakota, USA, with a sequence of hot springs at low points around the perimeter, discharging through sandstones but with some of the world’s most extensive hypogene maze caves formed in a limestone karst barré setting behind them: (6) The Sierra de El Abra, at Lat. 23° N in Mexico, a deep and lengthy (100 km) reef-backreef limestone range being progressively exposed and karstified by stripping of a cover of clastic rocks; the springs are few but amongst the largest known in karst anywhere, located at the northern and southern low extremities along the strike of the reef, plus breaches (windows) in the cover further south.

Shape variation of Aegla schmitti (Crustacea, Decapoda, Aeglidae) associated to superficial and subterranean stream reaches, 2013,
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Camile Fernandes, Maria Bichuette

The species Aegla schmitti is relatively abundant in epigean streams in the Upper Ribeira Basin, southeastern Brazil and has a few records in caves. In this study, we questioned if those individuals would be an accidental presence or could be populations already established in cave streams? In this case, would morphological variations be associated with superficial and subterranean stream reaches? In this exploratory survey we tried to answer these questions by assessing the shape variation of cephalothorax using landmark-based geometric morphometrics. Different shapes were found for both environments, evidencing a successful hypogean colonization. The area effect was discarded as being the unique factor responsible for the divergence, therefore, for the first time in the literature, here we report morphological modifications associated with subterranean colonization in troglophiles. We also conceived and discussed some hypotheses about the colonization.

‘Looping caves’ versus ‘water table caves’: The role of base-level changes and recharge variations in cave development, 2014,
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Gabrovšek Franci, Häuselmann Philipp, Audra Philippe

The vertical organisation of karst conduit networks has been the focus of speleogenetic studies for more than a century. The four state model of Ford and Ewers (1978), which still is considered as the most general, relates the geometry of caves to the frequency of permeable fissures. The model suggests that the ‘water table caves’ are common in areas with high fissure frequency, which is often the case in natural settings. However, in Alpine karst systems, water table caves aremore the exception than the rule. Alpine speleogenesis is influenced by high uplift, valley incision rates and irregular recharge. To study the potential role of these processes for speleogenesis in the dimensions of length and depth, we apply a simple mathematical model based on coupling of flow, dissolution and transport.We assume a master conduit draining thewater to the spring at a base level. Incision of the valley triggers evolution of deeper flow pathways,which are initially in a proto-conduit state. Themaster conduit evolves into a canyon following the valley incision,while the deep pathways evolve towards maturity and tend to capture the water fromthe master conduits. Two outcomes are possible: a) deep pathways evolve fast enough to capture all the recharge, leaving the master conduit dry; or b) the canyon reaches the level of deep pathways before these evolve to maturity. We introduce the Loop-to-Canyon Ratio (LCR), which predicts which of the two outcomes is more likely to occur in certain settings. Our model is extended to account for transient flow conditions. In the case of an undulating master conduit, floodwater is stored in troughs after the flood retreat. This water seeps through sub-vertical fractures (‘soutirages’) connecting the master conduitwith the deep pathways. Therefore, the loops evolve also during the dry season, and the LCR is considerably increased. Although themodel is based on several approximations, it leads to some important conclusions for vertical organisation of karst conduit networks and stresses the importance of base-level changes and transient recharge conditions. It therefore gives an explanation of speleogenesis that relies much more on the dynamic nature of water flow than on the static fracture density

Diatom flora in subterranean ecosystems: a review., 2014,
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In scarcity of light and primary producers, subterranean ecosystems are generally extremely oligotrophic habitats, receiving poor supplies of degradable organic matter from the surface. Human direct impacts on cave ecosystems mainly derive from intensive tourism and recreational caving, causing important alterations to the whole subterranean environment. In particular, artificial lighting systems in show caves support the growth of autotrophic organisms (the so-called lampenflora), mainly composed of cyanobacteria, diatoms, chlorophytes, mosses and ferns producing exocellular polymeric substances (EPSs) made of polysaccharides, proteins, lipids and nucleic acids. This anionic EPSs matrix mediates to the intercellular communications and participates to the chemical exchanges with the substratum, inducing the adsorption of cations and dissolved organic molecules from the cave formations (speleothems). Coupled with the metabolic activities of heterotrophic microorganisms colonising such layer (biofilm), this phenomenon may lead to the corrosion of the mineral surfaces. In this review, we investigate the formation of biofilms, especially of diatom-dominated ones, as a consequence of artificial lighting and its impacts on speleothems. Whenever light reaches the subterranean habitat (both artificially and naturally) a relative high number of species of diatoms may indeed colonise it. Cave entrances, artificially illuminated walls and speleothems inside the cave are generally the preferred substrates. This review focuses on the diatom flora colonising subterranean habitats, summarizing the information contained in all the scientific papers published from 1900 up to date. In this review we provide a complete checklist of the diatom taxa recorded in subterranean habitats, including a total of 363 taxa, belonging to 82 genera. The most frequent and abundant species recorded in caves and other low light subterranean habitats are generally aerophilic and cosmopolitan. These are, in order of frequency: Hantzschia amphioxys, Diadesmis contenta, Orthoseira roeseana, Luticola nivalis, Pinnularia borealis, Diadesmis biceps and Luticola mutica. Due to the peculiarity of the subterranean habitats, the record of rare or new species is relatively common. The most important environmental factors driving species composition and morphological modifications observed in subterranean populations are analysed throughout the text and tables. In addition, suggestions to prevent and remove the corrosive biofilms in view of an environmentally sustainable cave management are discussed.

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