共查询到20条相似文献,搜索用时 31 毫秒
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Kimberly B. Teehera Sean P. Jungbluth Bogdan P. Onac Tayro E. Acosta-Maeda Eric Hellebrand Anupam K. Misra 《Geomicrobiology journal》2018,35(3):227-241
The Mauna Loa volcano, on the Island of Hawaii, has numerous young lava tubes. Among them, two at high altitudes are known to contain ice year-round: Mauna Loa Icecave (MLIC) and the Arsia Cave. These unusual caves harbor cold, humid, dark, and biologically restricted environments. Secondary minerals and ice were sampled from both caves to explore their geochemical and microbiological characteristics. The minerals sampled from the deep parts of the caves, where near freezing temperatures prevail, are all multi-phase and consist mainly of secondary amorphous silica SiO2, cryptocrystalline calcite CaCO3, and gypsum CaSO4·2H2O. Based on carbon and oxygen stable isotope ratios, all sampled calcite is cryogenic. The isotopic composition of falls on the global meteoric line, indicating that little evaporation has occurred. The microbial diversity of a silica and calcite deposit in the MLIC and from ice pond water in the Arsia Cave was explored by analysis of ~50,000 small subunit ribosomal RNA gene fragments via amplicon sequencing. Analyses reveal that the Hawaiian ice caves harbor unique microbial diversity distinct from other environments, including cave environments, in Hawaii and worldwide. Actinobacteria and Proteobacteria were the most abundant microbial phyla detected, which is largely consistent with studies of other oligotrophic cave environments. The cold, isolated, oligotrophic basaltic lava cave environment in Hawaii provides a unique opportunity to understand microbial biogeography not only on Earth but also on other planets. 相似文献
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《Palaeogeography, Palaeoclimatology, Palaeoecology》1999,145(1-3):215-230
An Early to Late Miocene sequence of rodent assemblages from southern France has been quantitatively studied. The resulting pattern seems very similar to a contemporary sequence from central Spain (Calatayud–Teruel Basin). The fossil mammal-bearing localities are of different types: mainly karst infills in France and localities situated in sedimentary basins in Spain. In order to interpret the fossil record, a comparison has been made between southern France faunas of similar age but collected in karst infills and in basin deposits. There seems to be no difference between the two kinds of faunas and thus there is no indication that karst infills systematically give a picture of drier and more open environments. Both types of localities may give a similar relative abundance of taxa and when differences exist they can be attributed to local conditions. The comparison between southern France and the Calatayud–Teruel Basin (central Spain) shows that: (1) similar trends occurred in the two areas; (2) differences between spectra were more important during the late Early Miocene than during the Middle Miocene; (3) the shift between the late Early Miocene and the Middle Miocene environments in southern France does not seem to be correlated with a general drop in temperatures as inferred from the analysis of central Spain faunas. 相似文献
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We studied shoaling behaviour in a species of fish (Garra barreimiae) from Oman. We compared two populations (a surface-dwelling and a cave-dwelling population) with different theoretical costs and benefits of shoaling. We measured the tendency to associate with a shoal of conspecifics. The stimulus shoal was confined to (1) clear Plexiglas cylinders in light, (2) wire-mesh cylinders in light, or (3) wire-mesh cylinders in darkness. The surface form exhibited a strong preference for the stimulus shoal during the experiments in light, but also in darkness, when only non-visual cues from the shoal could be perceived. The cave form did not show a preference when solely visual cues were available (Plexiglas cylinder). When non-visual cues from the shoal could be perceived (wire-mesh), the cave form did show a preference to associate with the shoal, but the shoaling tendency was considerably weaker than in the surface form. The shoaling tendency has probably been genetically reduced in the cave form. 相似文献
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AbstractA comprehensive study was conducted from a semi-arid part of Yavtmal District, Maharashtra, India through combination approaches of geochemical modeling and its health consequences. The groundwater quality assessment shows that 55% of groundwater samples have the concentration of fluoride above the desirable limit. The high Na+/Ca+ ratio (>1.0) suggest the occurrence of cation exchange, which is further supported by Scholler’ chloro-alkaline indices. The geochemical modeling reveals that the existence of CaCO3 precipitation and CaF2 in groundwater. Simulation analysis indicates the dissolution of calcite, gypsum, and albite and precipitation of dolomite, fluorite, halite, and K-feldspar along with cation exchange as the main water–rock interactions influencing the groundwater chemistry. This is further significantly supported by pollution index of groundwater (PIG). PIG indicates about 18% of total samples fall in very high pollution zone, 3% in high pollution zone, 8% in moderate pollution zone, 24% in low pollution zone, and remaining (47%) express insignificant pollution. The 28% of subject studied have skeletal fluorosis varying from mild to severe type. In different pollution zones, the affected persons by dental fluorosis are varying from 15% to 41%. A proper monitoring and treatment are required for high fluoride water before its use for drinking and cooking. 相似文献
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Schwinning S 《Oecologia》2008,158(3):373-383
The ecohydrology of karst has not received much attention, despite the disproportionally large contribution of karst aquifers to freshwater supplies. Karst savannas, like many savannas elsewhere, are encroached by woody plants, with possibly negative consequences on aquifer recharge. However, the role of savanna tree species in hydrological processes remains unclear, not least because the location and water absorption zones of tree roots in the spatially complex subsurface strata are unknown. This study examined the water sources and water relations of two savanna trees, Quercus fusiformis (Small) and Juniperus ashei (Buchholz) in the karst region of the eastern Edwards Plateau, Texas (USA). Stable isotope analysis of stem water revealed that both species took up evaporatively enriched water during the warm season, suggesting a relatively shallow water source in the epikarst, the transition zone between soil and bedrock. Q. fusiformis had consistently higher predawn water potentials than J. ashei during drought, and thus was probably deeper-rooted and less capable of maintaining gas exchange at low water potentials. Although the water potential of both species recovered after drought-breaking spring and summer rain events, associated shifts in stem water isotope ratios did not indicate significant uptake of rainwater from the shallow soil. A hypothesis is developed to explain this phenomenon invoking a piston-flow mechanism that pushes water stored in macropores into the active root zones of the trees. Epikarst structure varied greatly with parent material and topography, and had strong effects on seasonal fluctuations in plant water status. The study suggests that tree species of the Edwards Plateau do not commonly reduce aquifer recharge by tapping directly into perched water tables, but more likely by reducing water storage in the epikarst. A more general conclusion is that models of savanna water relations based on Walter's two-layer model may not apply unequivocally to karst savannas. 相似文献
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Bacterial dynamics in spring water of alpine karst aquifers indicates the presence of stable autochthonous microbial endokarst communities 总被引:6,自引:0,他引:6
Farnleitner AH Wilhartitz I Ryzinska G Kirschner AK Stadler H Burtscher MM Hornek R Szewzyk U Herndl G Mach RL 《Environmental microbiology》2005,7(8):1248-1259
Spring water of two alpine karst aquifers differing in hydrogeology but of nearby catchments were investigated for their bacterial population dynamics. Dolomite karst aquifer spring 1 (DKAS 1) represents a dolomitic-limestone karst aquifer spring showing high average water residence time and relative constant flow. Limestone karst aquifer spring 2 (LKAS 2) constitutes a typical limestone karst aquifer spring with a dynamic hydrological regime and discharge. Dolomite karst aquifer spring 1 yielded constantly lower cell counts and biomasses (median of 15 x 10(6) cells l(-1) and 0.22 microg C l(-1)) as the LKAS 2 (median of 63 x 10(6) cells l(-1) and 1.1 microg C l(-1)) and distribution of morphotypes and mean cell volumes was also different between the considered systems, indicating the influence of hydrogeology on microbial spring water quality. Molecular bacterial V3 16S-rDNA profiles revealed remarkable constancy within each spring water throughout the investigation period. Time course analysis of a flood event in LKAS 2 further supported the trend of the temporal constancy of the microbial community. Except for one case, retrieval of partial and full length 16S rDNA gene sequences from the relative constant DKAS 1 revealed similarities to presently known sequences between 80% to 96%, supporting the discreteness of the microbial populations. The gathered results provide first evidence for the presence of autochthonous microbial endokarst communities (AMEC). Recovery of AMEC may be considered of relevance for the understanding of alpine karst aquifer biogeochemistry and ecology, which is of interest as many alpine and mountainous karst springs are important water resources throughout the world. 相似文献
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Peter M. Wynn Andrea Borsato Andy Baker Silvia Frisia Renza Miorandi Ian J. Fairchild 《Biogeochemistry》2013,114(1-3):255-267
Trace amounts of sulphur in speleothems suggest that stalagmites may act as archives of sulphur deposition, thereby recording aspects of atmospheric variability in sulphur content. Accurate interpretation of this novel sulphur archive depends upon understanding how biogeochemical cycling in the soil and epikarst above the cave may modify the precursor atmospheric values of sulphur concentration and isotopic composition prior to incorporation into the speleothem record. Dual isotope analysis of δ34S-SO4 and δ18O-SO4 is used to trace biogeochemical transformations of atmospheric sulphur through the cave system at Grotta di Ernesto in the Italian Alps and builds towards a framework for interpretation of speleothem sulphur archives which depends on overlying ecosystem dynamics and karst hydrological properties. A three component model of atmospheric sulphate signal modification is proposed to be driven by (1). vegetation and soil cycling, (2). the degree of groundwater mixing in the karst aquifer; and (3). redox status. The relative influence of each process is specific to individual drip flow sites and associated stalagmites, rendering each sulphur archive a unique signal of environmental conditions. Under conditions found in the soil and epikarst above Grotta di Ernesto, the dual isotope signatures of sulphate sulphur and oxygen incorporated into speleothem carbonate, closely reflect past conditions of industrial sulphur loading to the atmosphere and the extent of signal modification through biogeochemical cycling and aquifer mixing. 相似文献
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Identification of major sources controlling groundwater chemistry from a multilayered aquifer system
《Chemical Speciation and Bioavailability》2013,25(3):183-189
AbstractThe Maknassy basin is a typical example of an arid area in Central Tunisia. The geology of the area is mainly composed of Cretaceous calcareous formations. To identify the major process involved in controlling the groundwater chemistry, 53 groundwater samples for three different aquifer levels have been examined. The groundwater chemistry is dominated by SO4 (Na + Mg) and (Cl + SO4). The presence of (Ca + Mg) and (Na + K) with HCO3 indicates the domination of dolomitic rock weathering as the major source of cations. The plots for Na to Cl indicate a fine correlation and reflects their release from halite dissolution during groundwater transition. An ion exchange process is also activated in study area which is indicated by a shift to the right in a plot for Ca + Mg to SO4 + HCO3. The plot of Na – Cl to Ca + Mg – (HCO3 + SO4) confirms that Ca, Mg and Na concentrations in groundwater are derived from aquifer materials. Saturation indexes of groundwater samples indicate undersaturation for gypsum and anhydrite, and oversaturation for calcite, dolomite and aragonite confirming waterrock interactions by dissolution and dilution processes. In general, water chemistry is guided by weathering process, ion exchange and water-rock interaction during groundwater transition. 相似文献
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研究洞穴土壤节肢动物,有助于了解土壤节肢动物对特殊环境的响应,对于深入认识喀斯特生态过程具有重要意义。以喀斯特洞穴生态系统小型土壤节肢动物为研究对象,采用主成分分析、重复测量方差分析、相关性分析和冗余分析等方法探讨了小型土壤节肢动物与环境因子的相互作用关系。调查共获得小型土壤节肢动物2399个,隶属7纲15目121科。其中,自然林优势类群为等节跳科(Isotomidae),洞穴优势类群为奥甲螨科(Oppiidae)。PCA分析显示,洞穴与自然林小型土壤节肢动物群落组成差异明显。洞穴小型土壤节肢动物类群数、密度和Shannon-Wiener指数(H′)显著低于自然林(P<0.05),自然林小型土壤节肢动物类群数、密度和Shannon-Wiener指数(H′)季节差异显著(P<0.05),洞穴类群数、密度和Shannon-Wiener指数(H′)季节差异不明显。相关性分析结果表明,小型土壤节肢动物类群数和Shannon-Wiener指数(H′)与pH值、全磷和光照强度显著相关(P<0.05),密度与pH值、全磷、有机质和光照强度显著相关(P<0.05)。RDA分析表... 相似文献
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洞穴是喀斯特景观中普遍存在的地质地貌结构, 拥有丰富的植物资源。仅2001-2020年间, 就发表了中国喀斯特洞穴维管植物新属1个; 新种(含种下等级) 170个, 隶属于16科31属, 占近20年发表的中国维管植物新种的3.9%, 说明洞穴植物具有较高的物种多样性潜力。据统计, 中国喀斯特洞穴维管植物有110科339属871种, 主要分布于广西、广东、贵州、云南、重庆等地。物种数排名前5的科包括苦苣苔科、荨麻科、鳞毛蕨科、秋海棠科和茜草科, 其所含物种数共占整个洞穴植物种类的39.4%; 排名前5的属包括报春苣苔属(Primulina)、楼梯草属(Elatostema)、耳蕨属(Polystichum)、秋海棠属(Begonia)和凤尾蕨属(Pteris), 其所含物种数共占整个洞穴植物种类的25.1%。本名录的所有洞穴植物中, 草本习性的种类占一半以上。从洞内分布来看, 仅有10.7%的种类分布于弱光带, 其中石松类和蕨类植物占比远高于被子植物, 说明前者更能适应弱光带的极端环境。不仅如此, 洞穴维管植物也具有较高的特有性成分, 其中省级特有种占比25.8%, 分别包括非洞穴特有种(11.0%)、多洞穴特有种(3.3%)和单洞穴特有种(11.5%)。依据文献显示受威胁种类有115种(占13.0%)。受威胁种类占比较高的类群均是近年来发表新种较多的科, 包括鳞毛蕨科、苦苣苔科、荨麻科、秋海棠科、茜草科等。针对这些类群, 有待更详细地调查来完善对它们的评估。此外, 本名录中至少有36%的种类没有任何分子数据, 亟待补充。 相似文献
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Shallow-marine microporous limestones account for many carbonate reservoirs. Their formation, however, remains poorly understood.
Due to the lack of recent appropriate marine analogues, this study uses a lacustrine counterpart to examine the diagenetic
processes controlling the development of intercrystalline microporosity. Late Miocene lacustrine microporous micrites of the
Madrid Basin (Spain) have a similar matrix microfabric as Cenomanian to Early Turonian shallow-marine carbonates of the Mishrif
reservoir Formation (Middle East). The primary mineralogy of the precursor mud partly explains this resemblance: low-Mg calcites
were the main carbonate precipitates in the Cretaceous seawater and in Late Miocene freshwater lakes of the Madrid Basin.
Based on hardness and petrophysical properties, two main facies were identified in the lacustrine limestones: a tight facies
and a microporous facies. The tight facies evidences strong compaction, whereas the microporous facies does not. The petrotexture,
the sedimentological content, and the mineralogical and chemical compositions are identical in both facies. The only difference
lies in the presence of calcite overgrowths: they are pervasive in microporous limestones, but almost absent in tight carbonates.
Early diagenetic transformations of the sediment inside a fluctuating meteoric phreatic lens are the best explanation for
calcite overgrowths precipitation. Inside the lens, the dissolution of the smallest crystals in favor of overgrowths on the
largest ones rigidifies the sediment and prevents compaction, while partly preserving the primary microporous network. Two
factors appear essential in the genesis of microporous micrites: a precursor mud mostly composed of low-Mg calcite crystals
and an early diagenesis rigidifying the microcrystalline framework prior to burial. 相似文献
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Nicholas T. Loux David S. Brown Claudia R. Chafin Jerry D. Allison Sayed M. Hassan 《Chemical Speciation and Bioavailability》2013,25(3):111-125
AbstractCoupled geochemical speciation/transport models are being developed to assess potential transport of metal contaminants in the subsurface environment. In a test of the geochemical speciation portion of the effort, MINTEQA2 model predictions are compared with laboratory data concerning the pH dependent partitioning behavior of eight cationic contaminants (Ba, Be, Cd, Cu, Ni, Pb, Tl and Zn) on a sandy aquifer material in an oxidized environment. MINTEQA2 contains provisions for describing potential attenuation due to both mineral phase precipitation processes and adsorption processes resulting from amorphous iron oxides in aquifer materials (MIT Diffuse Layer Model). In the comparison, several trends were discerned. (1) Adsorptive processes tend to better describe the pH-dependent partitioning behavior of transition metals (especially Pb, Zn and Ni). (2) Cd behavior is better described by precipitation as a cadmium carbonate phase. (3) Cu behavior is not reasonably described by the model. (4) Ba and Be comparisons are poor (although presumably their partitioning behavior results from adsorptive and/or pH sensitive solid solution processes). (5) unlike the other elements, the behavior of Tl is relatively insensitive to pH. 相似文献
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猿人洞的溶洞演化和堆积旋回与北京猿人生活环境 总被引:4,自引:1,他引:3
猿人洞的溶洞演化过程按岩溶洞穴发生发展规律可划分为6个阶段.在洞穴发育的填充过程中,依据堆积物的成因类型,猿人洞中的中更新世洞穴堆积层可分为7个堆积旋回.每个堆积旋回可与年代相当的黄土堆积旋回和深海气候旋回—一对应.堆积旋回所显示的气候和洞穴环境变化均与北京猿人生活环境及其旧石器文化的发展有着密切的关系. 相似文献
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The timing of desertification of the Sahara Desert is poorly understood, with recent estimates indicating an onset of hyper-aridity during the Latest Miocene. Field work in Egypt in 2005 has led to the discovery of evidence that indicates that 11–10 Ma the Western Desert was covered in woodland. Fossiliferous cave breccia at Sheikh Abdallah, Western Desert, Egypt, has yielded a Late Miocene (11–10 Ma) microvertebrate fauna, which contains Galagidae, Microchiroptera, Macroscelididae, Soricidae, Erinaceidae, and Rodentia. The locality also yielded the remains of frogs, snakes, lizards, and birds. The fauna indicates a mean annual rainfall in excess of 500 mm and perhaps as much as 1,200 mm. This palaeoclimatic information is important because it reveals that the Sahara Desert, which is today the largest in the world, was either considerably smaller during the Late Miocene than it is today, or that it did not yet exist as a continuous hyper-arid belt right across the continent. This data accords with estimates of a Latest Miocene (8–7 Ma) increase in aridity in the Sahara. To cite this article: M. Pickford et al., C. R. Palevol 5 (2006). 相似文献
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Bakermans C Hohnstock-Ashe AM Padmanabhan S Padmanabhan P Madsen EL 《Microbial ecology》2002,44(2):107-117
We used geochemical analyses of groundwater and laboratory-incubated microcosms to investigate the physiological responses
of naturally occurring microorganisms to coal-tar-waste constituents in a contaminated aquifer. Waters were sampled from wells
along a natural hydrologic gradient extending from uncontaminated (1 well) into contaminated (3 wells) zones. Groundwater
analyses determined the concentrations of carbon and energy sources (pollutants or total organic carbon), final electron acceptors
(oxygen, nitrate, sulfate), and metabolic byproducts (dissolved inorganic carbon [DIC], alkalinity, methane, ferrous iron,
sulfide, Mn2+). In the contaminated zone of the study site, concentrations of methane, hydrogen, alkalinity, and DIC were
enhanced, while dissolved oxygen and nitrate were depleted. Field-initiated biodegradation assays using headspace-free serum
bottle microcosms filled with groundwater examined metabolism of the ambient organic contaminants (naphthalene, 2-methylnaphthalene,
benzothiophene, and indene) by the native microbial communities. Unamended microcosms from the contaminated zone demonstrated
the simultaneous degradation of several coal-tar-waste constituents at the in situ temperature (10°C). Lag phases prior to
the onset of biodegradation indicated the prevalence of both aerobic and anaerobic conditions in situ. Electron acceptor-amended
microcosms from the most contaminated well waters demonstrated only aerobic naphthalene degradation. Collectively, the geochemical
and microbial evidence show that biodegradation of coal-tar-waste constituents occurs via both aerobic and anaerobic terminal
electron accepting processes at this site. 相似文献
18.
Larvae of the genus Arachnocampa, known as glowworms, are bioluminescent predatory insects that use light to attract prey. One species, Arachnocampa flava, is known to possess true circadian regulation of bioluminescence: light:dark cycles entrain the rhythm of nocturnal glowing. Given the absence of natural light as a cue in caves, we addressed the question of whether cave populations of Arachnocampa tasmaniensis, a species known to inhabit caves as well as epigean environments, are rhythmic. We found that the major dark-zone cave populations of A. tasmaniensis maintain a high-amplitude 24-hour rhythm of bioluminescence, with the acrophase during external daylight hours. Populations of A. tasmaniensis in caves many kilometers apart show similar, but not exactly the same, timing of the acrophase. Systematic investigation of colonies in the dark zone of a single cave showed that some smaller colonies distant to the main ceiling colony, also in the dark zone, glow in antiphase. Periodic monitoring of a single colony over several years showed that the acrophase shifted from nocturnal to diurnal some time between October 2008 and January 2009. Prey availability was investigated as a possible zeitgeber. The acrophase of prey availability, as measured by light trapping, and the acrophase of bioluminescence do not precisely match, occurring 3 hours apart. Using in-cave artificial light exposure, we show that after LD cycles, cave larvae become entrained to bioluminesce during the foregoing photophase. In contrast, epigean larvae exposed to artificial LD cycles after a period of DD become entrained to bioluminesce during the foregoing scotophase. One explanation is that individuals within colonies in the dark zone synchronize their bioluminescence rhythms through detection and matching of each other 's bioluminescence. 相似文献
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Caves and karsts are among the most threatened ecosystems in the world. They are very fragile, balanced habitats with high levels of endemic species that are extremely sensitive to environmental changes. In recent decades, however, threats from rapid economic growth have increased the need for conservation efforts for cave-dwelling communities. In addition, difficulties in accessing and sampling these habitats mean that they remain as one of the least known ecosystems in the world with modern studies of cave fishes only starting in China during the 1980s. Here, the current status of cave fishes in China is reviewed. China is host to the highest number of cave fish species in the world, with 48 troglobite species out of a total of 101 cave fish species. All of these cave fish species (one order and three families) and half of the genera are endemic to China with Sinocyclocheilus being the most speciose cave fish genus. Species from this genus possess horns and humpbacks resulting from processes of parallel evolution, but the function of these features remains unknown. With the exception of Onychostoma macrolepis distributed in north China, all other species are found in the karst environment of the Yunnan-Guizhou Plateau. Sympatric distribution is common, and sometimes several different cave fish species can be found in the same cave or subterranean river. For this reason, Chinese cave fishes represent an important evolutionary framework. 相似文献
20.
K. M. Liang Z. F. Lin H. Ren N. Liu Q. M. Zhang J. Wang Z. F. Wang L. L. Guan 《Photosynthetica》2010,48(4):494-506
Primulina tabacum Hance is an endangered perennial herb distributed in calcium-rich and nitrogen-limited soil of the karst limestone areas
in southern China. The morphological, ultrastructural, and physiological traits were determined for P. tabacum populations growing in three different environment conditions: twilight zone of a cave (site TZ, extremely low light intensity),
at a cave entrance (site EZ, low light intensity), and in an open area (site OA, high light intensity). At site OA, P. tabacum plants were exposed to high light (635 μmol m−2 s−1 of mean daily photosynthetically active radiation) with drought stress, and expressed traits to minimize light capture and
water loss. Compared to plants at sites EZ and TZ, those at site OA had thicker leaves with higher densities of stomata and
pubescence, higher palisade/spongy ratio, higher light-saturated rate of net photosynthetic rate (P
max), higher biomass, higher non-photochemical quenching coefficient (NPQ), and higher light saturation point (LSP) but fewer
grana per chloroplast and less thylakoid stacking per granum. In contrast, P. tabacum growing at the cave vicinities: EZ (mean daily irradiance 59 μmol m−2 s−1) and TZ (mean daily irradiance 11 μmol m−2 s−1) showed typical shade-adapted characteristics for optimum light capture. The presence of sun- and shade-adapted characteristics
indicates that P. tabacum has different strategies to cope with different environments but whether these strategies reflect genetic selection or phenological
plasticity is yet to be determined. Such variability in physiological and morphological traits is important for the survival
of P. tabacum in heterogeneous light conditions. 相似文献