Structure and seasonal variability of fish food webs in an estuarine tropical marine protected area (Senegal): Evidence from stable isotope analysis     

Djibril Faye  Luis Tito de Morais  Jean Raffray  Oumar Sadio  Omar Thiom Thiaw  Franois Le Loc&#x;h 《Estuarine, Coastal and Shelf Science》2011,92(4):69

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Analysis of the spatial evolution of the 2003 algal bloom in the Voordelta (North Sea)     

Hendrik Jan van der Woerd  Anouk Blauw  Louis Peperzak  Reinold Pasterkamp  Steef Peters 《Journal of Sea Research》2011,65(2):195-204

Phaeocystis blooms in the Southern Bight of the North Sea may cause damage to the aquatic ecosystem and to commercial mussel cultures at the entrance of the Oosterschelde estuary. In this paper the potential for early detection of Phaeocystis blooms in Dutch coastal waters is studied, using a combination of field data, satellite observations and hydrodynamic- and biological modelling. For the spring bloom period in the year 2003 MERIS chlorophyll-a maps, derived with the HYDROPT algorithm for coastal waters, were compared to in-situ measurements at stations off the coast in de Voordelta and the results of the GEM biogeochemical model.The analysis shows that the spatial and temporal variability in Phaeocystis abundance and total biomass (expressed by the Chl-a concentration) during spring is large. It is confirmed that blooms may develop off shore and show a tendency to accumulate within 10 km from the coastline, giving rise to rapid biomass accumulation at the mouth of the multiple estuaries in the Voordelta. Based on the outcome of this study an early warning system is proposed that notifies local water managers and shellfish growers for potentially harmful Phaeocystis bloom formation.  相似文献   

岔巴沟、大理河与无定河水土保持减水减沙作用的尺度效应   总被引：2，自引：0，他引：2  

綦俊谕  蔡强国  蔡乐  孙莉英 《地理科学进展》2011,30(1):95-102

运用经验公式法、双累积曲线法和不同系列对比法计算出岔巴沟、大理河与无定河流域在20世纪70年代水土保持综合措施的平均减水效益分别为14.47%、20.22%和20.78%,平均减沙效益为64.97%、43.62%和47.26%.对计算结果进行分析发现,用3种方法对岔巴沟、大理河与无定河流域水土保持综合措施减水减沙效益的...  相似文献   

The possibilities and pitfalls presented by a pragmatic approach to ecosystem service valuation in an arid biodiversity hotspot     

P.J. O’Farrell  W.J. De LangeD.C. Le Maitre  B. ReyersJ.N. Blignaut  S.J. MiltonD. Atkinson  B. EgohA. Maherry  C. ColvinR.M. Cowling 《Journal of Arid Environments》2011,75(6):612-623

Arid regions are home to unique fauna, flora, and vulnerable human populations, and present a challenge for sustainable land-use management. We undertook an assessment and valuation of three key services, grazing, tourism and water supply in the arid Succulent Karoo biome in western South Africa - a globally recognised biodiversity hotspot. We were looking for ways and values that could be used to promote conservation in this region through the adoption of sustainable land-use practices which have human welfare benefits. Our study adopted a variety of methods in valuing these services in developing ranges of values for these services. At the biome level, total annual values ranged from $ 19-114 million for grazing, $ 2-$ 20 million for tourism, and $ 300-3120 million for water. These values are generally low compared with values derived for other biomes and regions and do not adequately reflect known dependence and the importance of ecosystem services to the residents of this biome. The ecosystems here provide small but critical benefits enabling communities to sustain themselves and small changes in service levels can have major welfare effects. Highlighting these sensitivities will require finding more appropriate ways to link ecological and social factors.  相似文献   

The formation of a detached shell around the carbon star Y CVn     

Y. Libert  E. Gérard  T. Le Bertre 《Monthly notices of the Royal Astronomical Society》2007,380(3):1161-1171

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Improving the seeing with wide-field adaptive optics in the near-infrared     

M. Le Louarn  N. Hubin 《Monthly notices of the Royal Astronomical Society》2006,365(4):1324-1332

In this paper, we present simulation results of a ground-layer correction adaptive optics system (GLAO), based on four laser guide stars and a single deformable mirror. The goal is to achieve a seeing improvement over an 8-arcmin field of view, in the near-infrared (from 1.06 to 2.2 μm). We show results on the scaling of this system (number of subapertures, frame rates), and the required number of tip-tilt stars. We investigate the use for GLAO of both sodium and Rayleigh guide stars. We also show that if the lasers can be repositioned, the performance of the adaptive optics can be tailored to the astronomical observations.  相似文献   

Ultraviolet photolysis of anthracene in H2O interstellar ice analogs: Potential connection to meteoritic organics     

Samantha F. M. ASHBOURN  Jamie E. ELSILA  Jason P. DWORKIN  Max P. BERNSTEIN  Scott A. SANDFORD  Louis J. ALLAMANDOLA 《Meteoritics & planetary science》2007,42(12):2035-2041

Abstract— The polycyclic aromatic hydrocarbon (PAH) anthracene was oxidized by exposure to ultraviolet (UV) radiation in H₂O ice under simulated astrophysical conditions, forming several anthracene ketones (9‐anthrone, 1,4‐anthraquinone, and 9,10‐anthraquinone) and alcohols (1‐anthrol and 2‐anthrol). Two of the ketones produced have been detected in the Murchison meteorite but, to our knowledge, there has been no search for the alcohols or other oxidized anthracenes in meteorites. These results seem consistent with the possibility that interstellar ice photochemistry could have influenced the inventory of aromatics in meteorites. Since quinones are also fundamental to biochemistry, their formation in space and delivery to planets is relevant to studies relating to the habitability of planets and the evolution of life.  相似文献   

Gamma–hadron separation methods for the VERITAS array of four imaging atmospheric Cherenkov telescopes     

H. Krawczynski  D.A. Carter-Lewis  C. Duke  J. Holder  G. Maier  S. Le Bohec  G. Sembroski 《Astroparticle Physics》2006,25(6):380-390

Ground-based arrays of imaging atmospheric Cherenkov telescopes have emerged as the most sensitive γ-ray detectors in the energy range of about 100 GeV and above. The strengths of these arrays are a very large effective collection area on the order of 10⁵ m², combined with excellent single photon angular and energy resolutions. The sensitivity of such detectors is limited by statistical fluctuations in the number of Cosmic-ray initiated air showers that resemble γ-ray air showers in many ways. In this paper, we study the performance of simple event reconstruction methods when applied to simulated data of the Very Energetic Radiation Imaging Telescope Array System (VERITAS) experiment. We review methods for reconstructing the arrival direction and the energy of the primary photons, and examine means to improve on their performance. For a software threshold energy of 300 GeV (100 GeV), the methods achieve point source angular and energy resolutions of σ_63% = 0.1° (0.2°) and σ_68% = 15% (22%), respectively. The main emphasis of the paper is the discussion of γ–hadron separation methods for the VERITAS experiment. We find that the information from several methods can be combined based on a likelihood ratio approach and the resulting algorithm achieves a γ–hadron suppression with a quality factor that is substantially higher than that achieved with the standard methods used so far.  相似文献   

The Zurich Extragalactic Bayesian Redshift Analyzer and its first application: COSMOS     

R. Feldmann  C. M. Carollo  C. Porciani  S. J. Lilly  P. Capak  Y. Taniguchi  O. Le Fèvre  A. Renzini  N. Scoville  M. Ajiki  H. Aussel  T. Contini  H. McCracken  B. Mobasher  T. Murayama  D. Sanders  S. Sasaki  C. Scarlata  M. Scodeggio  Y. Shioya  J. Silverman  M. Takahashi  D. Thompson  G. Zamorani 《Monthly notices of the Royal Astronomical Society》2006,372(2):565-577

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Late Glacial and Holocene vegetation history in the southern part of Transylvania (Romania): pollen analysis of two sequences from Avrig     

Ioan Tantau  Maurice Reille  Jacques‐Louis de Beaulieu  Sorina Farcas 《第四纪科学杂志》2006,21(1):49-61

We present here the results of pollen analysis of two sequences of about 8.06 m and 11.90 m length, originating from two adjacent peat bogs in the southern part of Transylvania province, Romania (155 and 122 pollen spectra). The vegetation record, which is supported by 17 ¹⁴C dates, begins in the Late Glacial interstadial when forest recolonisation began with the development of Pinus, without a pioneer Betula phase. Picea began to expand from regional refuges. After a well‐defined Younger Dryas, the Holocene opens with the expansion of Betula, Ulmus and Picea, followed, at about 10 400 cal. yr BP, by Fraxinus, Quercus and Tilia. The Corylus optimum is correlated with the Atlantic chronozone (after 8600 cal. yr BP). The local establishment of Carpinus occurred at about 6500 cal. yr BP, with a maximum at about 5700 cal. yr BP. Fagus pollen is regularly recorded after 8200 cal. yr BP. This taxon became dominant at about 3700 cal. yr BP. The first indications of human activities appear at around 7200 cal. yr BP. Copyright © 2005 John Wiley & Sons, Ltd.  相似文献