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101.
102.
Olivier Morissette Frédéric Lecomte Guy Verreault Michel Legault Pascal Sirois 《Estuaries and Coasts》2016,39(2):571-582
Migratory contingents, groups of individuals belonging to the same population that adopt different migratory patterns, have been identified in numerous Striped Bass (Morone saxatilis) populations along North American East Coast. We tested the hypothesis that migratory contingents may develop early in life to maximize the exploitation of the variety of habitats faced by a recently introduced fish population. Using the discriminatory power provided by otolith chemistry, we studied early-life history stages of Striped Bass in a recently reintroduced population in the St. Lawrence Estuary. Migratory patterns were inferred using multivariate analysis of four otolith trace elements (Sr, Ba, Mn, and Mg) on juveniles (0+ and 1+). Three migratory contingents were identified during early-life history stages: freshwater residents, oligohaline migrants, and mesohaline migrants. This study demonstrates the rapid establishment, in less than 10 years since initial stocking, of three migratory contingents initiated early in life among the St. Lawrence Striped Bass population. We postulate that diversification provided by the establishment of distinct migratory contingents among early-life history stages promotes the rapid colonization of new environments through the exploration and exploitation of an increased number of nursery habitats. 相似文献
103.
Gilles Poizat Elizabeth Rosecchi Philippe Chauvelon Pascal Contournet Alain J. Crivelli 《Estuarine, Coastal and Shelf Science》2004,59(4):615-624
The fish and macro-crustacean community of the Vaccarès lagoon (Rhône River delta, South France) was sampled monthly from 1993 to 2002. The lagoon salinity shifted from 15 in 1993 to 5 in 1994–1997 and went back to 15 in 1999–2002. Connections with the sea also varied during the study period with larger openings in 1996–1997. During the study period, the community changed to revert in 2002 to a state similar to 1993. These changes consisted of a sequence of increased and decreased patterns of freshwater species and some marine species. Typical lagoon species tended to resist to salinity changes. Freshwater species colonised the lagoon when the salinity was low. Marine species may have varied both in relation to connections with the sea and to indirect effects of freshwater outflow. This study shows that community changes following environmental variations can be delayed in time, and emphasises the need for long-term studies. 相似文献
104.
Why Is the Climate Forcing of Sulfate Aerosols So Uncertain? 总被引:2,自引:0,他引:2
l. IntroductionAlthough the aerosol has been recognized as an important factor which has innuence onthe past, present and future climate for a long time, it still has much uncertainty in assessingits climate forcing. The direct radiative forcing of sulfate aerosols has been estimated rangingfrom --0.3 W/ m2 to --0.9 W/ m2 in recent publications (Charlson et al., l992, Kiehl andBriegleb l993; Taylor and Penner 1994, Boucher and Anderson l995, Kieh1 and Rodhe l995;Chuang et al., l997, Penne… 相似文献
105.
Analytical Procedures for the Measurement of Boron Isotope Compositions by Ion Microprobe in Meteorites and Mantle Rocks 总被引:3,自引:1,他引:3
Marc Chaussidon François Robert Denis Mangin Pascal Hanon Estelle F. Rose 《Geostandards and Geoanalytical Research》1997,21(1):7-17
An analytical procedure has been developed to measure in situ the 11 B/10 B ratio in terrestrial basaltic rocks and meteoritic chondrules having B concentration of less than 1 μg g?1 using a small radius ims3f ion microprobe. The central difficulties for these measurements are (i) the removal of the trace amount of B contamination introduced in the sample during polishing, (ii) the precise calibration of instrumental mass fractionation of B isotopes and (iii) the low count rates of 10 B and 11 B. Contamination experiments conducted with isotopically labelled B enriched in 10 B showed that ultrasonic cleaning in bi-distilled water (< 1 ng g?1 B) and pre-sputtering of the analysed area decrease B contamination to the level of 0.01 μg g?1. Analyses of isotope standards spanning a range of 11 B/10 B between 3.93 and 4.20 showed that instrumental mass fractionation was constant within? during one session of analyses. Repeated analyses of a standard glass showed a reproducibility of instrumental mass fractionation between February 1991 and October 1996 of 1.3. Taking into account all sources of error, boron isotope measurements are accurate to within 5 for meteoritic samples having B contents in the range 0.1 to 1 μg g?1. A slightly better accuracy of 1.5 can be achieved for basaltic glasses which can be sputtered with very intense primary beams. 相似文献
106.
Anja Guhl Pascal Bertran Christoph Zielhofer Kathryn E. Fitzsimmons 《Boreas: An International Journal of Quaternary Research》2013,42(2):317-332
Two sand wedge structures and their host sediments, from Jonzac in SW France, were successfully dated using Optically Stimulated Luminescence (OSL) measurements on both small aliquots and single grains of quartz from the 180–212 μm size fraction. One of the sand wedges clearly contains primary infilling. However, grain‐size analysis and field observations do not clearly indicate whether the other feature represents a primary sand wedge or a composite sand wedge with primary and secondary infilling. OSL results and the geological setting justify using the Central Age Model (CAM) for the calculation of age estimates. Grain‐size analysis and detailed investigations of OSL results revealed the contamination of one sand wedge sample with host sediment. However, age calculation using the Finite Mixture Model (FMM) provided what is considered to be a reliable age estimate for the contaminated sample. The age estimates for all samples correspond to Marine Isotope Stage (MIS) 3. While fine‐grained sediments were deposited in the middle of MIS 3 (c. 43–55 ka), the sand wedges unexpectedly correspond to the end of this period (c. 33 ka) or the onset of MIS 2 (c. 27 ka). The sand wedges were probably formed during intense but short cold periods, possibly correlated with a Heinrich event (H2 and/or H3). The results help us to assess how effective luminescence dating is on sand wedges and the limitations involved in correlating sand wedge ages with Heinrich events, and contribute to the debate on the timing of cryogenic formation processes and the permafrost distribution in SW France. 相似文献
107.
108.
109.
Abstract— Ilafegh 013 is a slightly weathered, type-3 ordinary chondrite that is unusual in that it is highly shocked. Olivine grains in chondrules were studied in detail by transmission electron microscopy (TEM) to characterize the dislocations, fractures and recrystallization textures. Only c dislocations, in the (010) glide plane, seem to be activated by the shock wave. Fractures are more numerous in the TEM than at the scale of the optical microscope. They can be divided into two groups: (a) Open fractures with injections of molten metal, sulphide, and in some cases, phases containing Ca, Al, Na and K. (b) Very straight and narrow cracks parallel to {130} planes without injected material and consisting of imperfectly relaxed subgrain boundaries composed of two families of dislocations (Burgers vectors a and c ). Both types of dislocations are roughly in screw orientation (i.e., the subgrain boundaries have a pronounced twist character). It is suggested that they formed during the shock in order to relax stresses around shear fractures (fractures with displacements of their walls parallel to the fracture plane). Recrystallization occurs in areas where the dislocation density is high. Since diaplectic glass was not detected, it is suggested that recrystallization resulted from the large elastic energy of the lattice defects stored in the deformed crystals. 相似文献
110.
Recent advances on study of hadrosaurid dinosaurs in Heilongjiang(Amur) River area between China and Russia 下载免费PDF全文
Pascal Godefroit Pascaline Lauters Jimmy Van Itterbeeck Yuri L. Bolotsky Ivan Y. Bolotsky 《世界地质(英文版)》2011,(3):160-191
Four main dinosaur-bearing sites have been investigated in latest Cretaceous deposits from the Amur/Heilongjiang Region: Jiayin and Wulaga in China (Yuliangze Formation) ,Blagoveschensk and Kundur in Rus- sia (Udurchukan Formation) . More than 90% of the bones discovered in these localities belong to hollowcrested lambeosaurine hadrosaurids: Charonosaurus jiayinensis at Jiayin,Amurosaurus riabinini at Blagoveschensk, Olorotitan arharensis at Kundur,and Sahaliyania elunchunorum at Wulaga. Flat-headed hadrosaurine hadrosau- rids are much less numerous,but appear well diversified as well: Kerberosaurus manakini at Blagoveschensk, Wulagasaurus dongi at Wulaga,and a new genus at Kundur. Theropods are represented by shed teeth and isolated bones; isolated scutes and teeth discovered at Kundur are tentatively attributed to nodosaurids. Palynologi- cal studies suggest that these sites are probably synchronous with the Lancian’ vertebrate localities of western North America,which represent the youngest dinosaur faunas in this area. However,the latest Cretaceous dinosaur assemblages are completely different in the Amur/Heilongjiang region (lambeosaurines abundant,ceratopsids absent) and in western North America (ceratopsids abundant,lambeosaurines extremely rare or absent) . This probably reflects some kind of geographical barrier between both areas by Maastrichtian time rather than strong differences in palaeoecological conditions. 相似文献