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  • 1
    Publication Date: 2015-01-18
    Description: Mixing dissolution, a process whereby mixtures of two waters with different chemical compositions drive undersaturation with respect to carbonate minerals, is commonly considered to form cavernous macroporosity (e.g. flank margin caves and banana holes) in eogenetic karst aquifers. On small islands, macroporosity commonly originates when focused dissolution forms globular chambers lacking entrances to the surface, suggesting that dissolution processes are decoupled from surface hydrology. Mixing dissolution has been thought to be the primary dissolution process because meteoric water would equilibrate rapidly with calcium carbonate as it infiltrates through matrix porosity and because pCO 2 was assumed to be homogeneously distributed within the phreatic zone. Here, we report data from two abandoned well fields in an eogenetic karst aquifer on San Salvador Island, Bahamas, that demonstrate pCO 2 in the phreatic zone is distributed heterogeneously. The pCO 2 varied from less than log -2.0 to more than log -1.0 atm over distances of less than 30 m, generating dissolution in the subsurface where water flows from regions of low to high pCO 2 and cementation where water flows from regions of high to low pCO 2. Using simple geochemical models, we show dissolution caused by heterogeneously distributed pCO 2 can dissolve 2.5 to 10 times more calcite than the maximum amount possible by mixing of fresh water and seawater. Dissolution resulting from spatial variability in pCO 2 forms isolated, globular chambers lacking initial entrances to the surface, a morphology that is characteristic of flank margin caves and banana holes, both of which have entrances that form by erosion or collapse after cave formation. Our results indicate that heterogeneous pCO 2 , rather than mixing dissolution, may be the dominant mechanism for observed spatial distribution of dissolution, cementation and macroporosity generation in eogenetic karst aquifers and for landscape development in these settings. This article is protected by copyright. All rights reserved.
    Print ISSN: 0197-9337
    Electronic ISSN: 1096-9837
    Topics: Geography , Geosciences
    Published by Wiley
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  • 2
    Publication Date: 2012-10-13
    Description: Much of what is known about groundwater circulation and geochemical evolution in carbonate platforms is based on platforms that are fully confined or unconfined. Much less is known about groundwater flow paths and geochemical evolution in partially confined platforms, particularly those supporting surface water. In north-central Florida, sea level rise and a transition to a wetter climate during the Holocene formed rivers in unconfined portions of the Florida carbonate platform. Focusing on data from the Santa Fe River basin, we show river formation has led to important differences in the hydrological and geochemical evolution of the Santa Fe River basin relative to fully confined or unconfined platforms. Runoff from the siliciclastic confining layer drove river incision and created topographic relief, reorienting the termination of local and regional groundwater flow paths from the coast to the rivers in unconfined portions of the platform. The most chemically evolved groundwater occurs at the end of the longest and deepest flow paths, which discharge near the center of the platform because of incision of the Santa Fe River at the edge of the confining unit. This pattern of discharge of mineralized water differs from fully confined or unconfined platforms where discharge of the most mineralized water occurs at the coast. Mineralized water flowing into the Santa Fe River is diluted by less evolved water derived from shorter, shallower flow paths that discharge to the river downstream. Formation of rivers shortens flow path lengths, thereby decreasing groundwater residence times and allowing freshwater to discharge more quickly to the oceans in the newly formed rivers than in platforms that lack rivers. Similar dynamic changes to groundwater systems should be expected to occur in the future as climate change and sea level rise develop surface water on other carbonate platforms and low lying coastal aquifer systems. Copyright © 2012 John Wiley & Sons, Ltd.
    Print ISSN: 0885-6087
    Electronic ISSN: 1099-1085
    Topics: Architecture, Civil Engineering, Surveying , Geography
    Published by Wiley
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  • 3
    Publication Date: 2015-09-23
    Description: A key challenge in the quest toward an HIV-1 vaccine is design of immunogens that can generate a broadly neutralizing antibody (bnAb) response against the enormous sequence diversity of the HIV-1 envelope glycoprotein (Env). We previously demonstrated that a recombinant, soluble, fully cleaved SOSIP.664 trimer based on the clade A...
    Print ISSN: 0027-8424
    Electronic ISSN: 1091-6490
    Topics: Biology , Medicine , Natural Sciences in General
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  • 4
    Publication Date: 2014-03-20
    Description: ABSTRACT Most models of cave formation in limestone that remains near its depositional environment and has not been deeply buried (i.e. eogenetic limestone) invoke dissolution from mixing of waters that have different ionic strengths or have equilibrated with calcite at different p CO 2 values. In eogenetic karst aquifers lacking saline water, mixing of vadose and phreatic waters is thought to form caves. We show here calcite dissolution in a cave in eogenetic limestone occurred due to increases in vadose CO 2 gas concentrations and subsequent dissolution of CO 2 into groundwater, not by mixing dissolution. We collected high-resolution time series measurements (one year) of specific conductivity (SpC), temperature, meteorological data, and synoptic water chemical composition from a water table cave in central Florida (Briar Cave). We found SpC, p CO 2 and calcite undersaturation increased through late summer, when Briar Cave experienced little ventilation by outside air, and decreased through winter, when increased ventilation lowered cave CO 2(g) concentrations. We hypothesize dissolution occurred when water flowed from aquifer regions with low p CO 2 into the cave, which had elevated p CO 2 . Elevated p CO 2 would be promoted by fractures connecting the soil to the water table. Simple geochemical models demonstrate changes in p CO 2 of less than 1% along flow paths are an order of magnitude more efficient at dissolving limestone than mixing of vadose and phreatic water. We conclude that spatially or temporally variable vadose CO 2(g) concentrations are responsible for cave formation because mixing is too slow to generate observed cave sizes in the time available for formation. While this study emphasized dissolution, gas exchange between the atmosphere and karst aquifer vadose zones that is facilitated by conduits likely exerts important controls on other geochemical processes in limestone critical zones by transporting oxygen deep into vadose zones, creating redox boundaries that would not exist in the absence of caves. This article is protected by copyright. All rights reserved.
    Print ISSN: 0197-9337
    Electronic ISSN: 1096-9837
    Topics: Geography , Geosciences
    Published by Wiley
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  • 5
    Publication Date: 2012-10-27
    Description: ABSTRACT Formation of extensive phreatic caves in eogenetic karst aquifers is widely believed to require mixing of fresh and saltwater. Extensive phreatic caves also occur, however, in eogenetic karst aquifers where fresh and saltwater do not mix, for example in the upper Floridan aquifer. These caves are thought to have formed in their modern settings by dissolution from sinking streams or by convergence of groundwater flow paths on springs. Alternatively, these caves have been hypothesized to have formed at lower water tables during sea level low-stands. These hypotheses have not previously been tested against one another. Analyzing morphological data and water chemistry from caves in the Suwannee River Basin in north-central Florida and water chemistry from wells in the central Florida carbonate platform indicates that phreatic caves within the Suwannee River Basin most likely formed at lower water tables during lower sea levels. Consideration of the hydrological and geochemical constraints posed by the upper Floridan aquifer leads to the conclusion that cave formation was most likely driven by dissolution of vadose CO 2 gas into the groundwater. Sea level rise and a wetter climate during the mid-Holocene lifted the water table above the elevation of the caves and placed the caves 10s of meters below the modern water table. When rising water tables reached the land surface, surface streams formed. Incision of surface streams breached the pre-existing caves to form modern springs, which provide access to the phreatic caves. Phreatic caves in the Suwannee River Basin are thus relict and have no causal relationship with modern surficial drainage systems. Neither mixing dissolution nor sinking streams are necessary to form laterally extensive phreatic caves in eogenetic karst aquifers. Dissolution at water tables, potentially driven by vadose CO 2 gas, offers an underappreciated mechanism to form cavernous porosity in eogenetic carbonate rocks. Copyright © 2012 John Wiley & Sons, Ltd.
    Print ISSN: 0197-9337
    Electronic ISSN: 1096-9837
    Topics: Geography , Geosciences
    Published by Wiley
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  • 6
    Publication Date: 2014-02-11
    Description: The reorganization of patterns of species diversity driven by anthropogenic climate change, and the consequences for humans, are not yet fully understood or appreciated. Nevertheless, changes in climate conditions are useful for predicting shifts in species distributions at global and local scales. Here we use the velocity of climate change to derive spatial trajectories for climatic niches from 1960 to 2009 (ref. 7) and from 2006 to 2100, and use the properties of these trajectories to infer changes in species distributions. Coastlines act as barriers and locally cooler areas act as attractors for trajectories, creating source and sink areas for local climatic conditions. Climate source areas indicate where locally novel conditions are not connected to areas where similar climates previously occurred, and are thereby inaccessible to climate migrants tracking isotherms: 16% of global surface area for 1960 to 2009, and 34% of ocean for the 'business as usual' climate scenario (representative concentration pathway (RCP) 8.5) representing continued use of fossil fuels without mitigation. Climate sink areas are where climate conditions locally disappear, potentially blocking the movement of climate migrants. Sink areas comprise 1.0% of ocean area and 3.6% of land and are prevalent on coasts and high ground. Using this approach to infer shifts in species distributions gives global and regional maps of the expected direction and rate of shifts of climate migrants, and suggests areas of potential loss of species richness.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Burrows, Michael T -- Schoeman, David S -- Richardson, Anthony J -- Molinos, Jorge Garcia -- Hoffmann, Ary -- Buckley, Lauren B -- Moore, Pippa J -- Brown, Christopher J -- Bruno, John F -- Duarte, Carlos M -- Halpern, Benjamin S -- Hoegh-Guldberg, Ove -- Kappel, Carrie V -- Kiessling, Wolfgang -- O'Connor, Mary I -- Pandolfi, John M -- Parmesan, Camille -- Sydeman, William J -- Ferrier, Simon -- Williams, Kristen J -- Poloczanska, Elvira S -- England -- Nature. 2014 Mar 27;507(7493):492-5. doi: 10.1038/nature12976. Epub 2014 Feb 9.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Department of Ecology, Scottish Association for Marine Science, Scottish Marine Institute, Oban, Argyll, PA37 1QA, Scotland, UK. ; School of Science and Engineering, University of the Sunshine Coast, Maroochydore, Queensland QLD 4558, Australia. ; 1] Climate Adaptation Flagship, CSIRO Marine and Atmospheric Research, Ecosciences Precinct, GPO Box 2583, Brisbane, Queensland 4001, Australia [2] Centre for Applications in Natural Resource Mathematics (CARM), School of Mathematics and Physics, The University of Queensland, St Lucia, Queensland 4072, Australia. ; Department of Genetics, University of Melbourne, 30 Flemington Road, Parkville, Victoria 3010, Australia. ; Department of Biology, The University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599-3280, USA. ; 1] Institute of Biological, Environmental and Rural Sciences, Aberystwyth University, Aberystwyth SY23 3DA, UK [2] Centre for Marine Ecosystems Research, Edith Cowan University, Perth 6027, Australia. ; The Global Change Institute, The University of Queensland, Brisbane, Queensland 4072, Australia. ; 1] The UWA Oceans Institute, University of Western Australia, 35 Stirling Highway, Crawley 6009, Australia [2] Department of Global Change Research, IMEDEA (UIB-CSIC), Instituto Mediterraneo de Estudios Avanzados, Esporles 07190, Spain [3] Department of Marine Biology, Faculty of Marine Sciences, King Abdulaziz University, PO Box 80207, Jeddah 21589, Saudi Arabia. ; 1] Bren School of Environmental Science and Management, University of California, Santa Barbara, California 93106, USA [2] Imperial College London, Silwood Park Campus, Buckhurst Road, Ascot SL5 7PY, UK. ; Bren School of Environmental Science and Management, University of California, Santa Barbara, California 93106, USA. ; 1] GeoZentrum Nordbayern, Palaoumwelt, Universitat Erlangen-Nurnberg, Loewenichstrasse 28, 91054 Erlangen, Germany [2] Museum fur Naturkunde, Invalidenstr asse 43, 10115 Berlin, Germany. ; Department of Zoology and Biodiversity Research Centre, University of British Columbia, Vancouver V6T 1Z4, Canada. ; School of Biological Sciences, Australian Research Council Centre of Excellence for Coral Reef Studies, The University of Queensland, Brisbane, Queensland 4072, Australia. ; 1] Integrative Biology, University of Texas, Austin, Texas 78712, USA [2] Marine Institute, Drake Circus, University of Plymouth, Devon PL4 8AA, UK. ; Farallon Institute for Advanced Ecosystem Research, 101 H Street, Suite Q, Petaluma, California 94952, USA. ; Climate Adaptation Flagship, CSIRO Ecosystem Sciences, GPO Box 1700, Canberra, Australian Capital Territory 2601, Australia. ; Climate Adaptation Flagship, CSIRO Marine and Atmospheric Research, Ecosciences Precinct, GPO Box 2583, Brisbane, Queensland 4001, Australia.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/24509712" target="_blank"〉PubMed〈/a〉
    Keywords: *Animal Migration ; Animals ; Australia ; Biodiversity ; *Climate ; *Climate Change ; *Ecosystem ; *Geographic Mapping ; *Geography ; Models, Theoretical ; Population Dynamics ; Seawater ; Temperature ; Time Factors ; Uncertainty
    Print ISSN: 0028-0836
    Electronic ISSN: 1476-4687
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
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  • 7
    Electronic Resource
    Electronic Resource
    [s.l.] : Nature Publishing Group
    Nature 232 (1971), S. 393-394 
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] There is a background concentration of about 0.02 |ig/kg mercury in natural waters1-3, and some recent results4 showed values of 0.009-0.021 |ig/l. for essentially dissolved mercury in sea and river water. In regions of mercury mineralization5, however, up to 100 ug/kg has been reported. Similar ...
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  • 8
    Publication Date: 2001-07-24
    Print ISSN: 0027-8424
    Electronic ISSN: 1091-6490
    Topics: Biology , Medicine , Natural Sciences in General
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  • 9
    Publication Date: 2014-12-11
    Description: A peatland complex disturbed by berm construction in the 1950's was used to examine the long-term impact of water table (WT) manipulation on peatland hydraulic properties and moisture retention at three adjacent sites with increasing depth to WT (WET, INTermediate reference, and DRY). Saturated hydraulic conductivity ( K s ) was found to decrease with depth by several orders of magnitude over a depth of 1–1.5 m at all sites. The depth-dependence of WT response to rainfall was similar across sites: WT response increased from 1:1 at the surface, to 5:1 at 50 cm depth. While surface specific yield ( S y ) values were similar across all sites, it decreased with depth at a rate of 0.014 cm -1 in hollows and 0.007 cm -1 in hummocks. Bulk density ( ρ b ) exhibited similar depth-dependent trends as S y , and explains a high amount of variance (r 2  〉 0.69) in moisture retention across a range of pore water pressures (-15 to -500 cm H 2 O). Due to higher ρ b , hollow peat had greater moisture retention, where site effects were minimal. However, the estimated residual water content for surface Sphagnum samples, while on average lower in hummocks (0.082 m 3  m -3 ) versus hollows (0.087 m 3  m -3 ), increased from WET (0.058 m 3  m -3 ) to INT (0.088 m 3  m -3 ) to DRY (0.108 m 3  m -3 ) which has important implications for moisture stress under conditions of persistent WT drawdown. Given the potential importance of microtopographic succession for altering peatland hydraulic structure, our findings point to the need for a better understanding of what controls the relative height and proportional coverage of hummocks in relation to long-term disturbance-response dynamics. This article is protected by copyright. All rights reserved.
    Print ISSN: 0885-6087
    Electronic ISSN: 1099-1085
    Topics: Architecture, Civil Engineering, Surveying , Geography
    Published by Wiley
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  • 10
    Publication Date: 2009-04-29
    Print ISSN: 0018-067X
    Electronic ISSN: 1365-2540
    Topics: Biology
    Published by Springer Nature
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