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31.
Little is known about the effects of mud crabs population patterns on their exploitation. We used complementary approaches (experimental, fisher-based) to investigate how small-scale variations in density, size and sex-ratio related to the ecology of S. serrata may impact fishing practices in New Caledonia. Crabs were measured/sexed across 9 stations in contrasted mangrove systems between 2007 and 2009. Stations were described and classified in different kinds of mangrove forests (coastal, riverine, and estuarine); vegetation cover was qualitatively described at station scale. Annual catch was used as an indicator of fishing pressure. Middle-scale environmental factors (oceanic influence, vegetation cover) had significant contributions to crab density (GLM, 84.8% of variance), crab size and sex-ratio (< 30%). While small-scale natural factors contributed significantly to population structure, current fishing levels had no impacts on mud crabs. The observed, ecologically-driven heterogeneity of crab resource has strong social implications in the Pacific area, where land tenure system and traditional access rights prevent most fishers from freely selecting their harvest zones. This offers a great opportunity to encourage site-specific management of mud crab fisheries. 相似文献
32.
The contribution to the main detector counting rate from photons scattered and reemitted from the collimator walls is considered in two particular cases, that of our group's old S-11 rocket data and OSO-III. We find that the S-11 results are not changed appreciably white our consideration of the OSO-III results has lead us to the belief that these results should be strongly modified. 相似文献
33.
Julien Foriel Pascal Philippot Paul Dumas Murielle Salomé Bénédicte Ménez David Moreira 《Geochimica et cosmochimica acta》2004,68(7):1561-1569
Owing to the delicate nature of fossil microorganisms and inherent difficulties for discriminating true fossils from artifacts, an important challenge is to extract unequivocal biogenic information from individual microfossils using high-resolution, nondestructive and sensitive techniques. Here, we use combined synchrotron (X-ray microfluorescence, X-ray absorption near-edge structure and infrared microspectroscopies) and particle-induced X-ray emission analyses to image the spatial distribution at a μm-scale of a variety of potential biogenic markers (major and trace elements, C-H bonds, and sulfur-oxidation states) in individual prokaryotic microfossils. In particular, we analyzed iron-oxide fossil filaments of putative biogenic origin encapsulated with amorphous silica from a fragment of an inactive hydrothermal chimney of the East Pacific Rise. In order to test the biogenic origin of the markers studied, we performed the same analyses on filamentous bacteria corresponding most likely to the ?-Proteobacteria, and collected from substrates exposed to a hydrothermal fluid vent at the Mid-Atlantic Ridge. In both types of fossil and contemporary filaments, the occurrence of CH2 groups and of three sulfur species (sulfate, sulfite, organic S) showing heterogeneous distribution that underline the cytoplasm of individual cells in the case of the present-day filament, suggests that the original microorganisms were actively metabolizing sulfur. These results show the large potential of combining high-resolution synchrotron techniques to analyze individual microfossils for extracting unequivocal biogenic information. Furthermore, they also suggest that cooccurrence of different sulfur oxidation states within single microfossils could constitute a biogenic metabolic marker indicating S-metabolizing activities. 相似文献
34.
Kevin Grant Jannick Ingrin Jean Pierre Lorand Paul Dumas 《Contributions to Mineralogy and Petrology》2007,154(1):15-34
The speciation and amount of water dissolved in nominally anhydrous silicates comprising eight different mantle xenoliths
has been quantified using synchrotron micro-FTIR spectroscopy. Samples studied are from six geographic localities and represent
a cross-section of the major upper mantle lithologies from a variety of tectonic settings. Clinopyroxene contains between
342 and 413 ppm H2O. Orthopyroxene, olivine and garnet contain 169–201, 3–54 and 0 to <3 ppm H2O, respectively. Pyroxenes water contents and the distribution of water between ortho- and clinopyroxene is identical regardless
of sample mineralogy (D
watercpx/opx = 2.1 ± 0.1). The total water contents of each xenolith are remarkably similar (113 ± 14 ppm H2O). High-resolution spectroscopic traverses show that the concentration and speciation of hydrous defects dissolved in each
phase are spatially homogeneous within individual crystals and identical in different crystals interspersed throughout the
xenolith. These results suggest that the amount of water dissolved in the silicate phases is in partial equilibrium with the
transporting melt. Other features indicate that xenoliths have also preserved OH signatures of equilibrium with the mantle
source region: Hydroxyl stretching modes in clinopyroxene show that garnet lherzolites re-equilibrated under more reducing
conditions than spinel lherzolites. The distribution of water between pyroxenes and olivine differs according to xenolith
mineralogy. The distribution of water between clinopyroxene and olivine from garnet peridotites (D
watercpx/oliv(gnt) = 22.2 ± 24.1) is a factor of four greater than mineral pairs from spinel-bearing xenoliths (D
watercpx/oliv(sp) = 88.1 ± 47.8). Such an increase in olivine water contents at the spinel to garnet transition is likely a global phenomenon
and this discontinuity could lead to a reduction of the upper mantle viscosity by 0.2–0.7 log units and a reduction of its
electrical resistivity by a factor of 0.5–0.8 log units. 相似文献
35.
This study was aimed at modeling, as realistically as possible, the dynamics and thermodynamics of the Iroise Sea by using
the Model for Applications at Regional Scale (MARS), a regional ocean 3D model. The horizontal resolution of the configuration
in use is 2 km with 30 vertical levels. The 3D model of the Iroise Sea is embedded in a larger model providing open boundary
conditions. As regards the atmospheric forcing, the originality of this study is to force the regional ocean model with the
high-resolution (6 km) regional meteorological model, Weather Research and Forecasting (WRF). In addition, as the air surface
temperature is highly sensitive to the sea surface temperature (SST), this regional meteorological model is improved by taking
into account a regional climatologic SST to compute meteorological parameters. By allowing a better coherence between the
SST and the temperature of the atmospheric boundary layer while giving a more realistic representation of heat fluxes exchanged
at the air/sea interface, this forcing constitutes a noticeable improvement of the Iroise Sea modeling. The different sensitivity
tests discussed here pinpoint the importance of entering, in WRF, SST data of sufficiently high quality before the computation
of meteorological forcing when the aim is a study of dynamics and thermodynamics far away from the coast. On the other hand,
when the target is the reproduction of coastal small-scale features in Iroise Sea modeling, the resolution of the meteorological
forcing and the quality of SST are both paramount. The simulation of reference was carried out throughout the Summer and Autumn
of year 2005 to allow comparisons with a campaign of surface current measurements by high-frequency radars conducted at the
same period. 相似文献
36.
Sakina-Dorothée Ayata Céline Ellien Franck Dumas Stanislas Dubois Éric Thiébaut 《Continental Shelf Research》2009
The honeycomb worm Sabellaria alveolata forms biogenic reefs which constitute diversity hotspots on tidal flats. The largest known reefs in Europe, located in the Bay of Mont-Saint-Michel (English Channel), are suffering increasing anthropogenic disturbances which raise the question of their sustainability. As the ability to recover depends partly on the recolonization of damaged reefs by larval supply, evaluating larval dispersal and the connectivity between distant reefs is a major challenge for their conservation. In the present study, we used a 3D biophysical model to simulate larval dispersal under realistic hydroclimatic conditions and estimate larval retention and exchanges among the two reefs of different sizes within the bay. The model takes into account fine-scale hydrodynamic circulation (800×800 m2), advection–diffusion larval transport, and gregarious settlement behaviour. According to the field data, larval dispersal was simulated for a minimal planktonic larval duration ranging from 4 to 8 weeks and the larval mortality was set to 0.09 d−1. The results highlighted the role played by a coastal eddy on larval retention within the bay, as suggested by previous in situ observations. Very different dispersal patterns were revealed depending on the spawning reef location, although the two reefs were located only 15 km apart. The settlement success of the larvae released from the smallest reef was mainly related to tidal conditions at spawning, with the highest settlement success for releases at neap tide. The settlement success of the larvae from the biggest reef was more dependent on meteorological conditions: favourable W and SW winds may promote a ten-fold increase in settlement success. Strong year-to-year variability was observed in settlers’ numbers, with favourable environmental windows not always coinciding with the main reproductive periods of Sabellaria. Settlement kinetics indicated that the ability to delay metamorphosis could significantly improve the settlement success. Although bidirectional exchanges occurred between the two reefs, the highest settlers’ numbers originated from the biggest reef because of its stronger reproductive output. Because of the recent decline of this reef due to increasing anthropogenic disturbances larval supply in the bay may not be sufficient enough to ensure the sustainability of the remarkable habitat formed by Sabellaria alveolata reefs. 相似文献
37.
F. Merlin M.A. Barucci C. de Bergh F.E. DeMeo A. Alvarez-Candal C. Dumas D.P. Cruikshank 《Icarus》2010,210(2):930-943
We present new photometric and spectroscopic observations of the Pluto–Charon system carried out at the VLT-ESO (Chile) with two 8-m telescopes equipped with the FORS2, ISAAC and SINFONI instruments. The spectra were obtained in the 0.6–2.45 μm range with a spectral resolution from 300 to 1500. The SINFONI data were obtained using adaptive optics, allowing a complete separation of the two bodies. We derive both objects’ magnitudes in the near infrared and convert them into albedo values. These first near infrared photometric data allow to adjust the different parts of Pluto’s spectrum, provided by the three instruments. We run spectral models in order to give chemical and physical constraints on the surface of Pluto and Charon. We discuss the dilution properties of the methane ice and its implications on Pluto’s surface. The heterogeneities of the pure and diluted methane ice on Pluto’s surface is also investigated. The high signal-to-noise level of the data and our analyses may support the presence of ethane ice on the surface of Pluto, which is one of the main products of the methane irradiation and photolysis. The analyses of the spectra of Charon suggest that the water ice is almost completely in its crystalline form and that the ammonia compound is hydrated on the surface of this satellite. 相似文献
38.
C. E. Alissandrakis A. Kontogeorgos P. Tsitsipis C. Caroubalos X. Moussas P. Preka-Papadema A. Hilaris J. -L. Bougeret G. Dumas 《Earth, Moon, and Planets》2009,104(1-4):93-95
We present recent developments of the ARTEMIS IV solar radio spectrograph operating at Thermopylae, central Greece. Observations are obtained daily in total intensity and in the frequency range from 20 to 650 MHz, using two antennas and two receivers. We are now in the process of developing a new system that will record consecutively the intensity of right-hand and left-hand polarized waves using one of the antennas and the same receivers. 相似文献
39.
Assessing climate change impacts,sea level rise and storm surge risk in port cities: a case study on Copenhagen 总被引：8，自引：1，他引：7
Stéphane Hallegatte Nicola Ranger Olivier Mestre Patrice Dumas Jan Corfee-Morlot Celine Herweijer Robert Muir Wood 《Climatic change》2011,104(1):113-137
This study illustrates a methodology to assess the economic impacts of climate change at a city scale and benefits of adaptation,
taking the case of sea level rise and storm surge risk in the city of Copenhagen, capital of Denmark. The approach is a simplified
catastrophe risk assessment, to calculate the direct costs of storm surges under scenarios of sea level rise, coupled to an
economic input–output (IO) model. The output is a risk assessment of the direct and indirect economic impacts of storm surge
under climate change, including, for example, production and job losses and reconstruction duration, and the benefits of investment
in upgraded sea defences. The simplified catastrophe risk assessment entails a statistical analysis of storm surge characteristics,
geographical-information analysis of population and asset exposure combined with aggregated vulnerability information. For
the city of Copenhagen, it is found that in absence of adaptation, sea level rise would significantly increase flood risks.
Results call for the introduction of adaptation in long-term urban planning, as one part of a comprehensive strategy to manage
the implications of climate change in the city. Mitigation policies can also aid adaptation by limiting the pace of future
sea level rise. 相似文献
40.
Using the high-quality data set of 165 images taken at 11 epochs over the 5.13 h rotation of the large C-type Asteroid 511 Davida, we find the dimensions of its triaxial ellipsoid model to be 357±2×294±2×231±50 km. The images were acquired with the adaptive optics system on the 10 m Keck II telescope on December 27, 2002. The a and b diameters are much better determined than previously estimated from speckle interferometry and indirect measurements, and our mean diameter, (abc)1/3=289±21 km, is 19% below previous estimates. We find the pole to lie within 2° of [RA=295°; Dec=0°] or in Ecliptic coordinates [λ=297°; β=+21°], a significant improvement to the pole direction. Otherwise, previous determinations of the axial ratios agree with our new results. These observations illustrate that our technique of finding the dimensions and pole of an asteroid from its changing projected size and shape is very powerful because it can be done in essentially one night as opposed to decades of lightcurves. Average departures of 3% (5 km) of the asteroid's mean radius from a smooth outline are detected, with at least two local positive-relief features and at least one flat facet showing approximately 15 km deviations from the reference best-fit ellipsoid. The facet is reminiscent of large global-scale craters on Asteroid 253 Mathilde (also a C-type) when seen edge-on in close-up images from the NEAR mission flyby. We show that giant craters (up to 150 km diameter, the size of the largest facets seen on Davida) can be expected from the impactor size distribution, without likelihood of catastrophic disruption of Davida. 相似文献