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871.
Laure Moulin Ana Isabel Catarino Thomas Claessens Philippe Dubois 《Marine pollution bulletin》2011,62(1):48-54
The effect of pH ranging from 8.0 to 6.8 (total scale - pHT) on fertilization, cleavage and larval development until pluteus stage was assessed in an intertidal temperate sea urchin. Gametes were obtained from adults collected in two contrasting tide pools, one showing a significant nocturnal pH decrease (lowest pHT = 7.4) and another where pH was more stable (lowest pHT = 7.8). The highest pHT at which significant effects on fertilization and cleavage were recorded was 7.6. On the contrary, larval development was only affected below pHT 7.4, a value equal or lower than that reported for several subtidal species. This suggests that sea urchins inhabiting stressful intertidal environments produce offspring that may better resist future ocean acidification. Moreover, at pHT 7.4, the fertilization rate of gametes whose progenitors came from the tide pool with higher pH decrease was significantly higher, indicating a possible acclimatization or adaptation of gametes to pH stress. 相似文献
872.
Progress in some areas of process‐based aeolian sediment transport research is hampered by limited opportunities for data comparison, synthesis, and integration. This is partially due to a lack of reliable comparison methods. Many comparison methods are forms of calibration that are either restrictive (e.g., time‐averages only) or non‐existent (e.g., for field‐based sediment transport thresholds or vertical mass flux profiles). It is believed that the adoption of standard methods for common measurements may improve inter‐study comparison, add value and longevity to data, and advance integrative modeling efforts. Examples of approaches in allied disciplines where standards are used routinely are reviewed and we discuss how the mutual benefits of standardized data could outweigh perceived disadvantages. Overall, the goal of this commentary is to encourage discussion, self‐assessment, and forethought with regard to measurement methods used in process‐based aeolian geomorphology. Copyright © 2011 John Wiley & Sons, Ltd. 相似文献
873.
Synergy and fusion of optical and synthetic aperture radar satellite data for underwater topography estimation in coastal areas 总被引:1,自引:1,他引:0
Andrey Pleskachevsky Susanne Lehner Thomas Heege Claudius Mott 《Ocean Dynamics》2011,61(12):2099-2120
A method to obtain underwater topography for coastal areas using state-of-the-art remote sensing data and techniques worldwide
is presented. The data from the new Synthetic Aperture Radar (SAR) satellite TerraSAR-X with high resolution up to 1 m are
used to render the ocean waves. As bathymetry is reflected by long swell wave refraction governed by underwater structures
in shallow areas, it can be derived using the dispersion relation from observed swell properties. To complete the bathymetric
maps, optical satellite data of the QuickBird satellite are fused to map extreme shallow waters, e.g., in near-coast areas.
The algorithms for bathymetry estimation from optical and SAR data are combined and integrated in order to cover different
depth domains. Both techniques make use of different physical phenomena and mathematical treatment. The optical methods based
on sunlight reflection analysis provide depths in shallow water up to 20 m in preferably calm weather conditions. The depth
estimation from SAR is based on the observation of long waves and covers the areas between about 70- and 10-m water depths
depending on sea state and acquisition quality. The depths in the range of 20 m up to 10 m represent the domain where the
synergy of data from both sources arises. Thus, the results derived from SAR and optical sensors complement each other. In
this study, a bathymetry map near Rottnest Island, Australia, is derived. QuickBird satellite optical data and radar data
from TerraSAR-X have been used. The depths estimated are aligned on two different grids. The first one is a uniform rectangular
mesh with a horizontal resolution of 150 m, which corresponds to an average swell wavelength observed in the 10 × 10-km SAR
image acquired. The second mesh has a resolution of 150 m for depths up to 20 m (deeper domain covered by SAR-based technique)
and 2.4 m resolution for the shallow domain imaged by an optical sensor. This new technique provides a platform for mapping
of coastal bathymetry over a broad area on a scale that is relevant to marine planners, managers, and offshore industry. 相似文献
874.
Chunming Shi Valérie Masson-Delmotte Camille Risi Thomas Eglin Michel Stievenard Monique Pierre Xiaochun Wang Jing Gao François-Marie Bréon Qi-Bin Zhang Valérie Daux 《Earth and Planetary Science Letters》2011,301(1-2):307-316
We explore the potential of tree-ring cellulose δ18O and δ13C records for reconstructing climate variability in the southeast Tibetan Plateau. Our sampling strategy was designed to investigate intra and inter-tree variability, and the effects of the age of tree on δ18O variation. We show that intra-tree δ13C and δ18O variability is negligible, and inter-tree coherence is sufficient to build robust tree-ring δ18O or δ13C chronologies based on only four trees. There is no evidence of an age effect regarding δ18O, in contrast with tree-ring width. In our warm and moist sampling site, young tree δ13C is not clearly correlated with monthly mean meteorological data. Tree-ring δ18O appears significantly anti-correlated with summer precipitation amount, regional cloud cover, and relative humidity. Simulations conducted with the ORCHIDEE land surface model confirm the observed contribution of relative humidity to tree cellulose δ18O, and explain the weak correlation of δ13C with climate by the non-linear integration linked with photosynthesis. Altogether, the tree-ring cellulose δ18O is shown to be a promising proxy to reconstruct regional summer moisture variability prior to the instrumental period. 相似文献
875.
876.
The study of re-homogenized melt inclusions in the same growth planes of quartz of pegmatites genetically linked to the Variscan
granite of the Ehrenfriedersdorf complex, Erzgebirge, Germany, by ion microprobe analyses has determined high concentrations
of Be, up to 10,000 ppm, in one type of melt inclusion, as well as moderate concentrations in the 100 ppm range in a second
type of melt inclusion. Generally, the high Be concentrations are associated with the H2O- and other volatile-rich type-B melt inclusions, and the lower Be concentration levels are connected to H2O-poor type-A melt inclusions. Both inclusion types, representing conjugate melt pairs, are formed by a liquid–liquid immiscibility
separation process. This extremely strong and very systematic scattering in Be provides insights into the origin of Be concentration
and transport mechanisms in pegmatite-forming melts. In this contribution, we present more than 250 new analytical data and
show with ion microprobe and fs-LA-ICPMS studies on quenched glasses, as well as with confocal Raman spectroscopy of daughter
minerals in unheated melt inclusions, that the concentrations of Be may achieve such extreme levels during melt–melt immiscibility
of H2O-, B-, F-, P-, ± Li-enriched pegmatite-forming magmas. Starting from host granite with about 10 ppm Be, melt inclusions with
10,000 ppm Be correspond to enrichment by a factor of over 1,000. This strong enrichment of Be is the result of processes
of fractional crystallization and further enrichment in melt patches of pegmatite bodies due to melt–melt immiscibility at
fluid saturation. We also draw additional conclusions regarding the speciation of Be in pegmatite-forming melt systems from
investigation of the Be-bearing daughter mineral phases in the most H2O-rich melt inclusions. In the case of evolved volatile and H2O-rich pegmatite systems, B, P, and carbonates are important for the enrichment and formation of stable Be complexes. 相似文献
877.
Nicolas D. Greber Beda A. Hofmann Igor M. Villa Thomas F. Nägler 《Geochimica et cosmochimica acta》2011,75(21):6600-6609
We analyzed the molybdenum (Mo) isotope compositions (IC) of 59 samples from two molybdenite mineralizations (Alpjahorn and Grimsel) and from a Mo-rich hydrothermal breccia (Grimsel) from the Aar Massif, Switzerland. The formation temperature of the Late Paleozoic Mo mineralizations (300-600 °C) is much higher than that of the Pliocene breccia (100-160 °C). The Mo IC of the molybdenites varies over 1.35‰. Even in a single hand specimen it spans 0.45‰, indicating that fractionation processes during molybdenite precipitation can vary on a cm scale. The Mo IC of most molybdenites analyzed here are significantly heavier than that of the host rock (δ98/95Mo = (0.05 ± 0.1)‰) and show a bimodal distribution centered around δ98/95Mo ≈ 1.1‰ and 0.2‰. This result rules out single stage Rayleigh fractionation as the relevant formation mechanism and instead, redox variations are suggested to be a main factor controlling the Mo IC of the studied high-temperature Mo deposits. The range of the Mo IC in one single deposit, the Alpjahorn, overlaps with the variation range of almost all other published values for Mo IC in Mo deposits. Compared to the molybdenites, the breccia shows an even wider variation of 3.0‰ (δ98/95Mo between −1.6‰ and +1.4‰). In contrast to the high-T molybdenite deposits, here the Mo was transported via oxidized surface waters into the breccia system, where it was reduced and precipitated. This indicates that oxidation and reduction of Mo complexes may lead to highly variable Mo IC in hydrothermal systems. 相似文献
878.
Jan P. Amend Thomas M. McCollom Wolfgang Bach 《Geochimica et cosmochimica acta》2011,75(19):5736-5748
Active deep-sea hydrothermal vents are hosted by a range of different rock types, including basalt, peridotite, and felsic rocks. The associated hydrothermal fluids exhibit substantial chemical variability, which is largely attributable to compositional differences among the underlying host rocks. Numerical models were used to evaluate the energetics of seven inorganic redox reactions (potential catabolisms of chemolithoautotrophs) and numerous biomolecule synthesis reactions (anabolism) in a representative sampling of these systems, where chemical gradients are established by mixing hydrothermal fluid with seawater. The wide ranging fluid compositions dictate demonstrable differences in Gibbs energies (ΔGr) of these catabolic and anabolic reactions in three peridotite-hosted, six basalt-hosted, one troctolite-basalt hybrid, and two felsic rock-hosted systems. In peridotite-hosted systems at low to moderate temperatures (<∼45 °C) and high seawater:hydrothermal fluid (SW:HF) mixing ratios (>10), hydrogen oxidation yields the most catabolic energy, but the oxidation of methane, ferrous iron, and sulfide can also be moderately exergonic. At higher temperatures, and consequent SW:HF mixing ratios <10, anaerobic processes dominate the energy landscape; sulfate reduction and methanogenesis are more exergonic than any of the aerobic respiration reactions. By comparison, in the basalt-hosted and felsic rock-hosted systems, sulfide oxidation was the predominant catabolic energy source at all temperatures (and SW:HF ratios) considered. The energetics of catabolism at the troctolite-basalt hybrid system were intermediate to these extremes. Reaction energetics for anabolism in chemolithoautotrophs—represented here by the synthesis of amino acids, nucleotides, fatty acids, saccharides, and amines—were generally most favorable at moderate temperatures (22-32 °C) and corresponding SW:HF mixing ratios (∼15). In peridotite-hosted and the troctolite-basalt hybrid systems, ΔGr for primary biomass synthesis yielded up to ∼900 J per g dry cell mass. The energetics of anabolism in basalt- and felsic rock-hosted systems were far less favorable. The results suggest that in peridotite-hosted (and troctolite-basalt hybrid) systems, compared with their basalt (and felsic rock) counterparts, microbial catabolic strategies—and consequently variations in microbial phylotypes—may be far more diverse and some biomass synthesis may yield energy rather than imposing a high energetic cost. 相似文献
879.
The Portneuf–Mauricie Domain (PMD), located in the south-central part of the Grenville province, contains Mesoproterozoic
Ni–Cu ± platinum-group element (PGE) prospects hosted in a variety of plutonic intrusions (layered, with simple structures,
or zoned) and emplaced in a mature island arc setting. A two-stage model is envisaged to explain the formation of magmatic
sulfides. An early loss of a small amount of sulfides in the conduits of primitive, hydrous mantle-derived melts under high
fO2, resulted in depletion of the magmas in chalcophile and precious metals (Cu/Pd ratios vary from initial mantle values up
to 1.6 × 106). Then, nearer the mineralized zones, the magmas interacted with sulfide-bearing country rocks, resulting in felsification
of the magmas, assimilation of crustal sulfur (δ
34S values up to +5.5‰), and the formation of an immiscible sulfide liquid. Liquid-sulfide formation was followed by variable
interactions between the silicate and sulfide magmas, which were responsible for the enrichment of sulfides in Ni, Cu, and,
locally, PGE. Indeed, low R factors are found for prospects hosted in intrusions with a simple internal structure and in layered intrusions whereas high
R factors are found for prospects hosted in zoned intrusions. Finally, sulfide melt may have been partly incorporated into
later pulses of magma and injected into shallow magma chambers to form the PMD prospects. The PMD prospects share common characteristics
with other well-known deposits (Aguablanca, Vammala, Stormyrplunen, and deposits in Alaskan/Ural-type intrusions), attesting
to the Ni, Cu, and PGE potential of deposits associated with subduction-zone settings. 相似文献
880.
Woodrow B. Thompson Carol B. Griggs Norton G. Miller Robert E. Nelson Thomas K. Weddle Taylor M. Kilian 《Quaternary Research》2011,75(3):552-565
Excavations in the late-glacial Presumpscot Formation at Portland, Maine, uncovered tree remains and other terrestrial organics associated with marine invertebrate shells in a landslide deposit. Buds of Populus balsamifera (balsam poplar) occurred with twigs of Picea glauca (white spruce) in the Presumpscot clay. Tree rings in Picea logs indicate that the trees all died during winter dormancy in the same year. Ring widths show patterns of variation indicating responses to environmental changes. Fossil mosses and insects represent a variety of species and wet to dry microsites. The late-glacial environment at the site was similar to that of today's Maine coast. Radiocarbon ages of 14 tree samples are 11,907 ± 31 to 11,650 ± 50 14C yr BP. Wiggle matching of dated tree-ring segments to radiocarbon calibration data sets dates the landslide occurrence at ca. 13,520 + 95/−20 cal yr BP. Ages of shells juxtaposed with the logs are 12,850 ± 65 14C yr BP (Mytilus edulis) and 12,800 ± 55 14C yr BP (Balanus sp.), indicating a marine reservoir age of about 1000 yr. Using this value to correct previously published radiocarbon ages reduces the discrepancy between the Maine deglaciation chronology and the varve-based chronology elsewhere in New England. 相似文献