Influence of slight differences in environmental conditions (light, hydrodynamics) on the structure and function of periphyton     

A. Villeneuve  B. Montuelle  A. Bouchez 《Aquatic Sciences - Research Across Boundaries》2010,72(1):33-44

Small streams are ecosystems mainly controlled by physical factors. Minor differences in these factors can affect periphyton, which are key functional communities in these ecosystems. Eight different environmental conditions combining two types of current, two flow velocities and two light intensities were produced and controlled in artificial channels. Their impact on young and mature periphyton was investigated during a 6-week exposure period. The two different levels of light intensity produced early effects on the algal community. In young periphyton, the lower level of light intensity enhanced the number of algal cells, and this community appeared to be significantly structured by light. As the periphyton matured, the effects of physical factors became more marked. At this later stage, both the bacterial and algal communities began to be affected. Both function (primary production) and structure began to respond to differences in light and in flow velocity. Small differences in low-level environmental factors, such as light and flow, had an effect both on the structure of periphyton and its functional capacities. Keeping in mind the close link between diversity and function in microbial communities, periphyton confronted to various environmental stresses (pollution, flooding) in the field may behave differently due to minor differences in physical factors.  相似文献   

A new experimental technique for extracting liquids from peridotite at very low degrees of melting: application to partial melting of depleted peridotite   总被引：4，自引：0，他引：4  

Didier?LaporteEmail author  Michael?J.?Toplis  Monique?Seyler  Jean-Luc?Devidal 《Contributions to Mineralogy and Petrology》2004,146(4):463-484

A new technique that allows extraction of liquids from peridotite at degrees of melting as low as 0.2 wt% is presented. Microfractures that formed in the graphite sample container at the beginning of the experiments were used as traps for the liquid phase. Glass-filled cracks (or 'microdikes') unaffected by quench crystallisation were produced in all experiments and were analysed using standard electron microprobe techniques. Reversal experiments demonstrated that, at moderate degrees of melting (4.4 and 6.5 wt%), the segregated liquid was in equilibrium with the neighbouring peridotite. At very low degrees of melting (0.3 wt%), the liquid in the microdikes failed to fully equilibrate with the peridotite after 5 days and the sandwich technique was used in combination with the microdike technique to approach more closely the equilibrium composition of near-solidus partial melts. The microdike technique was used to study melting of a depleted peridotite at 1 GPa and 1,220 to 1,360 °C.Editorial responsibility: T.L. Grove  相似文献   

Discussion of “Monazite ages and the evolution of the Menderes Massif, western Turkey” (Int J Earth Sci 94:204–217)     

Donna L. Whitney  Jean-Luc Régnier 《International Journal of Earth Sciences》2006,95(2):350-351

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Origine des eaux des émergences karstiques chlorurées du Languedoc-Roussillon     

Olivier Hébrard  Séverin Pistre  Nicolas Cheynet  Jean Dazy  Christelle Batiot-Guilhe  Jean-Luc Seidel 《Comptes Rendus Geoscience》2006,338(10):703-710

The origin of chloride-rich karstic spring waters representative of the Languedoc-Roussillon region has been investigated with a hydrochemical approach. To this end, the major and trace elements most often used in the study of saline environments have been considered (Cl, SO₄, Br, B, Li). This study allowed distinguishing the different end-members of the various chloride-rich karstic spring waters (evaporitic, marine, geothermal). Associated with the Cl, Br and B contents, the Li/SO₄ ratio appeared as a relevant tracer for the determination of the origin of lithium and by extension of the considered waters. To cite this article: O. Hébrard et al., C. R. Geoscience 338 (2006).  相似文献   

Extraction of water and solutes from argillaceous rocks for geochemical characterisation: Methods, processes and current understanding     

Elisa Sacchi  Jean-Luc Michelot  Helmut Pitsch  Philippe Lalieux  Jean-François Aranyossy 《Hydrogeology Journal》2001,9(1):17-33

This paper summarises the results of a comprehensive critical review, initiated by the OECD/NEA "Clay Club," of the extraction techniques available to obtain water and solutes from argillaceous rocks. The paper focuses on the mechanisms involved in the extraction processes, the consequences on the isotopic and chemical composition of the extracted pore water and the attempts made to reconstruct its original composition. Finally, it provides some examples of reliable techniques and information, as a function of the purpose of the geochemical study. Electronic Publication  相似文献   

Structure and emplacement of granite plutons in the Paleoproterozoic crust of Eastern Burkina Faso: rheological implications     

Nestor Vegas  Seta Naba  Jean Luc Bouchez  Mark Jessell 《International Journal of Earth Sciences》2008,97(6):1165-1180

The Fada N′Gourma area in Burkina Faso is underlain by Paleoproterozoic rocks that make the northeastern West-African Craton. This region is composed of NE-trending volcano-sedimentary belts and foliated tonalites, affected by several shear zones. A generation of younger, ∼2100 Ma-old, non-foliated biotite-bearing granites intrudes the former rock units. We have investigated the younger granite pluton of Kouare that was previously considered as forming a single body with the pluton of Satenga to the west, a pluton which likely belongs to the ∼20 Ma more recent Tenkodogo-Yamba batholith. Magnetic fabric measurements have been combined with microstructural observations and the analysis of field and aeromagnetic data. The granite encloses angular enclaves of the host tonalites. Magmatic microstructures are preserved inside the pluton and solid-state, high-temperature deformation features are ubiquitous at its periphery. The presence of steeply plunging lineations in the pluton of Kouare and its adjacent host-rocks suggests that large volumes of granitic magmas became crystallized while they were ascending through the crust that was softened and steepened close to the contact. Around Kouare, the foliation in the host tonalites conforms with a map-scale, Z-shaped fold in between NNE-trending shear zones, implying a bulk clockwise rotation of the material contained in-between the shear zones, including the emplacing pluton. Regionally, the Fada N′Gourma area is concluded to result from NW-shortening associated with transcurrent shearing and vertical transfer of granitic magmas. This study concludes that the ∼2200 Myears old juvenile crust of Burkina Faso was brittle before the intrusion of the biotite-granites, became softened close to them and that gravity-driven and regional scale wrench tectonics were active together.  相似文献   

Nankai Trough, Japan Trench and Kuril Trench: geochemistry of Fluids sampled by submersible “Nautile”     

Jacques Boulgue  Jean T. Iiyama  Jean-Luc Charlou  Jacques Jedwab 《Earth and Planetary Science Letters》1987,83(1-4)

Deep-water samples collected during the Kaiko project are often associated with biological communities located on geological structures favorable to fluid venting. The evidence of fluid venting are the temperature anomalies, the decrease in sulfate concentrations, the content in methane and the lowC₁(C₂ +C₃) ratio of light hydrocarbons. Because of large dilution by ambiant seawater during sampling it is difficult to compute the composition of the advected end-member pore fluid. Part of this fluid should originate in the “petroleum window”, i.e. at temperature about 60°C. Modeling the upward flow of water, taking into account the anomalies of temperature measured on the seafloor and the geochemical anomalies, leads to non-steady-state advection of the pore fluid. The occurrence of a deep component in the fluid has implications for the geological and tectonic models of the subduction zones off Japan.  相似文献   

Interpretation cinematique des deformations plastiques dans le massif de Lherzolite de lanzo (Alpes piemontaises) — comparaison avec d'autres Massifs     

A. NicolasJ.L. Bouchez  F. Boudier 《Tectonophysics》1972

A map of internal movements into the Lherzolite Massif of Lanzo (shear planes, movement directions, shear senses, estimation of movements intensity) has been drawn from systematic measurements of plastic deformation elements (foliation planes, enstatite lineations, shear senses and angles, grain size of the rocks) which have been taken both in the field and laboratory. Since the deformation is probably due to the intrusion of the massif, these results contribute to knowledge of the orogenic displacements in this area of the Alpine system.  相似文献   

The Early Aptian Grünten Member: Description of a new lithostratigraphic unit of the helvetic Garschella Formation     

Pascal Linder  Johann Gigandet  Jean-Luc Hüsser  Fran?ois Gainon  Karl B. F?llmi 《Eclogae Geologicae Helvetiae》2006,99(3):327-341

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Mediterranean Sea and anthropogenic influences on ambient vibration amplitudes in the low-frequency and high-frequency domains in the Algiers region     

Rabah Bensalem  Jean-Luc Chatelain  Djamel Machane  El Hadi Oubaiche  Assia Bouchelouh  Nassima Benkaci  Hakim Moulouel  Souhila Chabane  Mustapha Hellel 《Arabian Journal of Geosciences》2017,10(13):282

Ambient vibrations have been continuously recorded at Dar El Beida, about 20 km from Algiers (Algeria). This data set allows determining that, in the low-frequency domain (<1 Hz), ambient vibration sources are mainly linked to Mediterranean Sea effects, while in the high-frequency domain, they are closely related to anthropogenic activity. Climatic conditions have an influence on the ambient vibration spectral amplitudes in the low-frequency domain, which is not the case in the high-frequency domain. The limit between the low-frequency and high-frequency domain, based on natural versus anthropogenic activity, is not clear cut and lies between 1.25 and 1.50 Hz. Variations of H/V peak amplitudes in the low-frequency domain are clearly linked to the climatic conditions. In the high-frequency domain, H/V peaks are not related to climatic conditions and cannot be clearly related to anthropogenic source changes.  相似文献