Seasonal and depth-dependent variations in the size and lipid contents of stage 5 copepodites of Calanus finmarchicus in the waters of the Newfoundland Shelf and the Labrador Sea     

Pierre Pepin  Erica J.H. Head 《Deep Sea Research Part I: Oceanographic Research Papers》2009,56(6):989-1002

We report on the variation in energy reserves of individual C5 copepodites of Calanus finmarchicus from the Newfoundland continental shelf and the Labrador Sea collected from surface and overwintering (or bottom) depths prior to, during and after the expected timing of the onset of diapause. Overall, the trend was for a decreasing average prosome length as the year progressed for all locations although the decline was smallest in the Labrador Sea and greatest in the deep waters of the continental shelf. The size of the oil sac was closely linked to the weight of the copepodite but the form of this relationship showed substantial variations with depth and season. We show a clear increase in the relative oil sac volume for C. finmarchicus between late spring and late summer, by which time some animals had descended to diapause depths. The progressive decrease in oil sac volume of animals sampled at depth in the Labrador Sea between September and December suggests a significant loss of energy reserves during diapause. From the distribution of volumes and body sizes in December we estimate that 23–53% of individuals would not be able to meet the energetic cost of moulting and early gonad development. Overall, some of our observations appear to invalidate earlier hypotheses concerning the governing role of lipids in the life history of C. finmarchicus. However, assessment of the factors that influence entry into dormancy should be based on the relative probabilities of alternative strategies for successful reproduction (e.g. entering dormancy vs. continuing into a second generation).  相似文献   

Identifying parameters controlling soil delayed behaviour from laboratory and in situ pressuremeter testing     

Zhen‐Yu Yin  Pierre‐Yves Hicher 《国际地质力学数值与分析法杂志》2008,32(12):1515-1535

The aim of this paper is to present a methodology for identifying the soil parameters controlling the delayed behaviour from laboratory and in situ pressuremeter tests by using an elasto‐viscoplastic model (EVP‐MCC) based on Perzyna's overstress theory and on the elasto‐plastic Modified Cam Clay model. The influence of both the model parameters and the soil permeability was studied under the loading condition of pressuremeter tests by coupling the proposed model equations with Biot's consolidation theory. On the basis of the parametric study, a methodology for identifying model parameters and soil permeability by inverse analysis from three levels of constant strain rate pressuremeter tests was then proposed and applied on tests performed on natural Saint‐Herblain clay. The methodology was validated by comparing the optimized values of soil parameters and the values of the same parameters obtained from laboratory test results, and also by using the identified parameters to simulate other tests on the same samples. The analysis of the drainage condition and the strain rate effect during a pressuremeter test demonstrated the coupled influence of consolidation and viscous effects on the test results. The numerical results also showed that the inverse analysis procedure could successfully determine the parameters controlling the time‐dependent soil behaviour. Copyright © 2008 John Wiley & Sons, Ltd.  相似文献   

Finite elements modelling of the long‐term behaviour of a full‐scale flexible pavement with the shakedown theory     

Cyrille Chazallon  Fatima Allou  Pierre Hornych  Saida Mouhoubi 《国际地质力学数值与分析法杂志》2009,33(1):45-70

  相似文献   

Observations of the North Equatorial Current,Mindanao Current,and Kuroshio current system during the 2006/07 El Niño and 2007/08 La Niña   总被引：1，自引：0，他引：1  

Yuji Kashino  Norievill España  Fadli Syamsudin  Kelvin J. Richards  Tommy Jensen  Pierre Dutrieux  Akio Ishida 《Journal of Oceanography》2009,65(3):325-333

Two onboard observation campaigns were carried out in the western boundary region of the Philippine Sea in December 2006 and January 2008 during the 2006/07 El Niño and the 2007/08 La Niña to observe the North Equatorial Current (NEC), Mindanao Current (MC), and Kuroshio current system. The NEC and MC measured in late 2006 under El Niño conditions were stronger than those measured during early 2008 under La Niña conditions. The opposite was true for the current speed of the Kuroshio, which was stronger in early 2008 than in late 2006. The increase in dynamic height around 8°N, 130°E from December 2006 to January 2008 resulted in a weakening of the NEC and MC. Local wind variability in this region did not appear to contribute to changes in the current system.  相似文献   

Macrofaunal density and biomass in the Campeche Canyon, Southwestern Gulf of Mexico     

Elva Escobar Briones  Erika Laura Estrada Santilln  Pierre Legendre 《Deep Sea Research Part II: Topical Studies in Oceanography》2008,55(24-26):2679

The composition, density and community structure of the benthic macrofauna were investigated in sediments of the Campeche Canyon in the SW Gulf of Mexico. Total macrofaunal density ranged from 9466±2736 ind m⁻² at the continental shelf station to 1550±195 ind m⁻² in the canyon. Density values significantly diminished with distance from the coast and depth; only a few stations in the center of the canyon displayed larger density values (E-37 with 4666±1530 ind m⁻², E-36 with 5791±642 ind m⁻² and E-26 with 6925±2258 ind m⁻²). Densities were positively correlated to organic nitrogen in the sediment (r=0.82) and coarse silt (r=0.43), and negatively with depth (r=−0.74) and distance from the coast (r=−0.68). At all stations, the polychaete worms contributed most to the multi-species community structure. The nematodes and Foraminifera displayed their highest densities in the center of the canyon. The biomass values declined significantly with depth. We conclude that the macrofauna density and biomass changed in response to organic matter contents in the sediment, both with distance from the coast and with depth.  相似文献   

Food web structure of two Mediterranean lagoons under varying degree of eutrophication   总被引：2，自引：0，他引：2  

Antoine Carlier  Pascal Riera  Jean-Michel Amouroux  Jean-Yves Bodiou  Martin Desmalades  Antoine Grmare 《Journal of Sea Research》2008,60(4):264-275

The food web structure and functioning of two north-western Mediterranean lagoons exhibiting contrasting degrees of eutrophication and marine influences were compared through δ¹³C and δ¹⁵N analysis of major potential food sources and consumers. The Lapalme Lagoon is well preserved and has kept a natural and temporary connection with the open sea. Conversely, the Canet Lagoon is heavily eutrophicated and its water exchange with the open sea has been artificially reduced. In Lapalme, all potential food sources and consumers exhibited δ¹⁵N values indicative of pristine coastal areas. Suspended particulate organic matter (POM) and sediment organic matter (SOM) pools seemed to constitute the main food sources of most primary consumers. Both primary producers and all consumers were much more ¹⁵N-enriched (by  10‰) and more ¹³C-depleted in Canet than in Lapalme. This reflected: (1) the assimilation of important amounts of anthropogenic nitrogen in the food web, and (2) a marked and uniform influence of ¹³C-depleted allochtonous sources of carbon. Based on the mean δ¹⁵N of primary consumers, we found rather similar food web lengths in both lagoons with top consumers at trophic levels 3.6 and 4.0 in Canet and Lapalme, respectively. However, the eutrophication of the Canet Lagoon resulted in a simplification of the food web structure (i.e., a single trophic pathway from a ¹⁵N-enriched fraction of the SOM pool to top predators) compared to what was observed in Lapalme Lagoon where additional ¹³C-enriched food sources played a significant trophic role. Moreover, some consumers of Canet tended to exploit primary producers to a larger extent (and thus to exhibit lower trophic levels) than in Lapalme.  相似文献   

Alteration geochemistry of the Nopal I uranium deposit (Sierra Peña Blanca,Mexico), a natural analogue for a radioactive waste repository in volcanic tuffs     

Georges Calas  Pierre Agrinier  Thierry Allard  Philippe Ildefonse 《地学学报》2008,20(3):206-212

Natural analogues provide an approach to characterize and test the long‐term modelling of a repository performance. This article presents geochemical information about the alteration conditions of the Nopal I uranium deposit, Mexico, an analogue for the proposed Yucca Mountain radioactive waste repository. Mineralization and hydrothermal alteration of volcanic tuffs are contemporaneous, according to petrographic observations. Trace element geochemistry (U, Th, REE) provides evidence for local mobilization of uranium under oxidizing conditions and further precipitation under reducing conditions. O‐ and H‐isotope geochemistry of kaolinite, smectite, opal and calcite suggests that argillic alteration proceeded at shallow depth with meteoric water at 25–75 °C, a low‐temperature context, unusual for volcanic‐hosted uranium deposits. This temperature range is compatible with some post‐closure evolution models of the proposed Yucca Mountain repository.  相似文献   

Diet of Haplognathia ruberrima (Gnathostomulida) in a Caribbean marine mangrove          下载免费PDF全文

Pierre‐Yves Pascal  Claude Bellemare  Wolfgang Sterrer  Henricus T. S. Boschker  Silvina Gonzalez‐Rizzo  Olivier Gros 《Marine Ecology》2015,36(2):246-257

Haplognathia ruberrima is a cosmopolitan gnathostomulid species found in sulfur bacterial mats in mangroves in Guadeloupe (French West Indies). Haplognathia ruberrima presents a δ¹³C value lower than all measured meiofaunal grazers and lower than the available measured food sources of this environment. This low δ¹³C value can not be due to specific ingestion of ¹³C‐depleted methanogenic bacteria because abundances of those bacteria are reduced in surficial and deep sediments as revealed by δ¹³C of bacterial fatty acid. According to scanning electron microscope observations, no bacterial ectosymbionts were observed at the surface of the gnathostomulids, and transmission electron microscope views revealed the absence of bacterial endosymbionts. Energy‐dispersive X‐ray spectroscopy analysis detected low levels of sulfur (0.32%±0.8) in biological tissues of H. ruberrima, confirming the absence of thioautotrophic bacterial symbionts in these animals. Consequently, the low δ¹³C value of H. ruberrima can not be due to the presence of sulfur‐oxidizing symbionts but more probably to the selective and exclusive consumption of free‐living, sulfur‐oxidizing bacteria.  相似文献   

Integrative taxonomic description of Plakina kanaky,a new polychromatic sponge species from New Caledonia (Porifera: Homoscleromorpha)          下载免费PDF全文

César Ruiz  Julijana Ivanišević  Pierre Chevaldonné  Alexander V. Ereskovsky  Nicole Boury‐Esnault  Jean Vacelet  Olivier P. Thomas  Thierry Pérez 《Marine Ecology》2015,36(4):1129-1143

Four similar sponges of different colors, all unknown to science, were collected in submarine caves of New Caledonia. We aimed at determining whether the four chromotypes represented different species or phenotypic variations of a unique new species. We used an integrative taxonomic approach combining morphologic, molecular and metabolomic analyses. The main traits that define these specimens are a skeleton made of monolophose, trilophose and tetralophose calthrops only, high chemical diversity and a high abundance and diversity of prokaryotic symbionts. The symbiotic community includes two unique prokaryote morphotypes, which are described for the first time in Homoscleromorpha, and appeared to be vertically transmitted. Although several features slightly differ among chromotypes, the most parsimonious conclusion was to propose a single new species Plakina kanaky sp. nov. Our phylogenetic analysis indicated the paraphyly of the Plakina genus, with P. kanaky sp. nov. belonging to a clade that includes Plakina jani and Plakina trilopha. The present work demonstrates that integrative taxonomy should be used in order to revise the entire Plakinidae family and especially the non‐monophyletic genus Plakina.  相似文献   

Molecular and distribution data on the poorly known,elusive, cave mysid Harmelinella mariannae (Crustacea: Mysida)          下载免费PDF全文

Pierre Chevaldonné  Pierre‐Alexandre Rastorgueff  Defne Arslan  Christophe Lejeusne 《Marine Ecology》2015,36(3):305-317

Mediterranean underwater marine caves harbour abundant populations of several species of mysids that are increasingly used as biological models in ecological and evolutionary studies. One exception is the species Harmelinella mariannae, described in 1989 and then hardly ever again reported in the literature. We here provide the first data on the distribution of this poorly known taxon that, contrary to expectations for a rare brooding cave dweller, we now report from Madeira Island in the nearby Atlantic, to the easternmost parts of the Mediterranean. Brief behavioural observations are added, particularly its atypical solitary habits and its feeding behaviour as a high trophic level carnivore. Molecular characterization of the different specimens captured provided three sorts of information. Mitochondrial COI and 16S haplotypes suggest different colonization waves in the Mediterranean, with one group in the Eastern Basin, two in the Marseille region in the NW part of this sea, and another group with a very wide extension from Madeira to Liguria and Malta. Mitochondrial data also support that one of the groups in Marseille might have diverged as a cryptic species of Harmelinella. 18S rRNA gene displays a single common sequence to all specimens from the four groups, and seems to confirm the original proposed placement of this taxon within the subfamily Heteromysinae, not Leptomysinae.  相似文献