Combining indicator trends to assess ongoing changes in exploited fish communities: diagnostic of communities off the coasts of France   总被引：1，自引：1，他引：1  

Rochet  Marie-Joelle; Trenkel  Verena; Bellail  Robert; Coppin  Franck; Le Pape  Olivier; Mahe  Jean-Claude; Morin  Jocelyne; Poulard  Jean-Charles; Schlaich  Ivan; Souplet  Arnauld; Verin  Yves; Bertrand  Jacques 《ICES Journal of Marine Science》2005,62(8):1647-1664

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Seasonal succession of cyanoprokaryotes in a hypereutrophic oligo-mesohaline lagoon from the South of France   总被引：2，自引：0，他引：2  

Nicolas Chomrat  Robert Garnier  Cline Bertrand  Arlette Cazaubon 《Estuarine, Coastal and Shelf Science》2007,72(4):591-602

The Bolmon lagoon (South of France) is an oligo-mesohaline coastal lagoon that has undergone intense eutrophication in the past decades, resulting from a strong concentration of human activities in its drainage basin. Consequently, it exhibits some characteristics typical of an advanced trophic state; namely, the disappearance of submerged vegetation, the permanently intense phytoplankton growth and the recurrence of cyanoprokaryote blooms. As cyanoprokaryote dominance in south-temperate saline lagoons is little reported, we carried out this study in order to understand the seasonal variations in the phytoplankton composition and biomass, and to analyse the influence of environmental parameters such as salinity, nutrients and climate on the seasonal succession of species. In this lagoon, the phytoplankton was permanently dominated by cyanoprokaryotes, probably because of high availability of nutrients, low light penetration in the water column and frequent turbulent mixing induced by wind. The two most abundant species Planktothrix agardhii (in winter–spring) and Pseudanabaena limnetica (in summer) have low light requirements and are well adapted to a high mixing frequency, which defines the S1 functional group in Reynolds' typology for phytoplankton. Although widely studied in north-temperate lakes, blooms of these typically freshwater species are almost unreported in the Mediterranean area, especially in brackish ecosystems that are not their normal habitat. In the Bolmon lagoon, all their requirements for nutrients, light and mixing are satisfied and they seem to cope with a moderate presence of salt but P. agardhii was less competitive than P. limnetica at highest salinities, the latter being probably more halophytic. Contrary to the observations in lakes located at higher latitudes, the Mediterranean climate seems to induce a typical seasonal pattern of succession characterised by the dominance of P. agardhii (winter) – Chroococcales (spring) – Pseudanabaenaceae (summer) – P. agardhii (autumn, winter). The warm temperatures seemed to have a major influence on the phytoplankton succession, being responsible for the survival of Planktothrix during winter and its rapid and intense development in early spring. Intense mixing and high irradiance in summer promoted the development of Pseudanabaenaceae, as reported in another south-temperate lagoon, the Albufera of Valencia (Spain). The ecological success of Oscillatoriales observed in the Bolmon lagoon is a perfect example of a shift to the “turbid stable state” as proposed for freshwater shallow lakes only. Our work demonstrated that hypereutrophic Mediterranean lagoons can function very similarly to shallow lakes at higher latitudes; but the warmer climate and higher irradiances are probably responsible for differences in the seasonal pattern of species dominance.  相似文献   

Fine resolution 3D temperature fields off Kerguelen from instrumented penguins     

Jean-Benoît Charrassin  Young-Hyang Park  Yvon Le Maho  Charles-Andr Bost 《Deep Sea Research Part I: Oceanographic Research Papers》2004,51(12):2091-2103

The use of diving animals as autonomous vectors of oceanographic instruments is rapidly increasing, because this approach yields cost-efficient new information and can be used in previously poorly sampled areas. However, methods for analyzing the collected data are still under development. In particular, difficulties may arise from the heterogeneous data distribution linked to animals’ behavior. Here we show how raw temperature data collected by penguin-borne loggers were transformed to a regular gridded dataset that provided new information on the local circulation off Kerguelen. A total of 16 king penguins (Aptenodytes patagonicus) were equipped with satellite-positioning transmitters and with temperature–time–depth recorders (TTDRs) to record dive depth and sea temperature. The penguins’ foraging trips recorded during five summers ranged from 140 to 600 km from the colony and 11,000 dives >100 m were recorded. Temperature measurements recorded during diving were used to produce detailed 3D temperature fields of the area (0–200 m). The data treatment included dive location, determination of the vertical profile for each dive, averaging and gridding of those profiles onto 0.1°×0.1° cells, and optimal interpolation in both the horizontal and vertical using an objective analysis. Horizontal fields of temperature at the surface and 100 m are presented, as well as a vertical section along the main foraging direction of the penguins. Compared to conventional temperature databases (Levitus World Ocean Atlas and historical stations available in the area), the 3D temperature fields collected from penguins are extremely finely resolved, by one order finer. Although TTDRs were less accurate than conventional instruments, such a high spatial resolution of penguin-derived data provided unprecedented detailed information on the upper level circulation pattern east of Kerguelen, as well as the iron-enrichment mechanism leading to a high primary production over the Kerguelen Plateau.  相似文献   

Multiple stock structure of Atlantic cod (Gadus morhua) off Newfoundland and Labrador determined from genetic variation   总被引：1，自引：0，他引：1  

Beacham  Terry D.; Brattey  John; Miller  Kristina M.; Le  Khai D.; Withler  Ruth E. 《ICES Journal of Marine Science》2002,59(4):650-665

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The Loyalty—New Hebrides Arc collision: Effects on the Loyalty Ridge and basin system,Southwest Pacific (first results of the ZoNéCo programme)     

Yves Lafoy  Francois Missegue  Dominique Cluzel  Raymond Le Suave 《Marine Geophysical Researches》1996,18(2-4):337-356

The ZoNéCo 1 and 2 cruises of Ifremer's Research Vessel L'Atalante, collected new swath bathymetry and geophysical data over the southern and northern segments of the basins and ridges forming the Loyalty system. Between the two surveyed areas, previous studies found evidence for the resistance of the Loyalty Ridge to subduction beneath the New Hebrides trench near 22°S–169°E. On the subducted plate, except for seismicity related to the downbending of the Australian plate, recorded shallow seismicity is sparse within the Loyalty system (Ridge and Basin) where reliable focal mechanism solutions are almost absent.Swath bathymetry, seismic reflection and magnetic data acquired during the ZoNéCo 1 and 2 cruises revealed a transverse asymmetric morphology in the Loyalty system, and an along-strike horst and graben structure on the discontinuous Loyalty Ridge. South of 23°50S and at 20°S, the two WSW-ENE-trending fault systems, respectively, sinistral and dextral, that crosscut the southern and northern segments of the Loyalty system, are interpreted as due to the early effects of collision with the New Hebrides Arc. A NNW-SSE trend, evident along the whole Loyalty system and on the island of New Caledonia, is interpreted as an inherited structural trend that may have been reactivated through flexure of the Australian lithospheric plate at the subduction zone.Overall then, the morphology, structure and evolution of the southern and northern segments of the Loyalty system probably result from the combined effects of the Australian plate lithospheric bulge, the active Loyalty-New Hebrides collision and the overthrust of the New Caledonian ophiolite.  相似文献   

Étude des grands bancs de sable du Sud-est de la mer Celtique     

Philippe Bouysse  Robert Horn  Francis Lapierre  François Le Lann 《Marine Geology》1976,20(3):251-275

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南海北部斑节对虾卵巢发育的形态及组织学观察   总被引：7，自引：0，他引：7  

黄建华  周发林  马之明  叶乐  江世贵 《热带海洋学报》2006,25(3):47-52

研究了南海北部斑节对虾Penaeus monodon卵巢发育的形态结构及组织学。以卵巢的组织学、性腺成熟指数(GSI)、卵巢的颜色和大小、卵细胞的直径、卵核的大小、形状、核仁的形态分布、不同发育阶段卵细胞数量比例等为参数,对南海北部斑节对虾卵巢发育的6个时期(卵原细胞期、染色质核仁期、周边核仁期、卵黄囊期、成熟期和恢复期)的组织结构特征进行了研究。并与菲律宾野生斑节对虾种群的卵巢组织结构特征进行了比较,发现2个地理种群的斑节对虾繁殖力存在一定差异。  相似文献   

Diel vertical behaviour, predator-prey relationships, and occupation of space by jack mackerel (Trachurus murphyi) off Chile   总被引：3，自引：0，他引：3  

Bertrand  Arnaud; Barbieri  Maria Angela; Cordova  Jose; Hernandez  Carola; Gomez  Fabian; Leiva  Francisco 《ICES Journal of Marine Science》2004,61(7):1105-1112

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The P-T-fO 2 stability of deerite,Fe 12 2+ Fe 6 3+ [Si12O40](OH)10     

Dominique Lattard  Nicole Le Breton 《Contributions to Mineralogy and Petrology》1994,115(4):474-487

New equilibrium experiments have been performed in the 20–27 kbar range to determine the upper thermal stability limit of endmember deerite, Fe ₁₂ ²⁺ Fe ₆ ³⁺ [Si₁₂O₄₀](OH)₁₀. In this pressure range, the maximum thermal stability limit is represented by the oxygen-conserving reaction: deerite(De)=9 ferrosilite(Fs)+3 magnetite(Mag)+3 quartz(Qtz)+5 H₂O(W) (1). Under the oxygen fugacities of the Ni-NiO buffer the breakdown-reduction reaction: De=12 Fs+2 Mag+5 W+1/2 O₂ (10) takes place at lower temperatures (e.g. T=63° at 27 kbar). The experimental brackets can be fitted using thermodynamic data for ferrosilite, magnetite and quartz from Berman (1988) and the following 1 bar, 298 K data for deerite (per gfw): V^o=55.74 J.bar^-1, S^o=1670 J.K^-1, H _f ^o =-18334 kJ, =2.5x10^-5K^-1, =-0.18x10^-5 bar^-1. Using these data in conjunction with literature data on coesite, grunerite, minnesotaite, and greenalite, the P-T stability field of endmember deerite has been calculated for P _s=P _{H 2}O. This field is limited by 6 univariant oxygenconserving dehydration curves, from which three have positive dP/dT slopes, the other three negative slopes. The lower pressure end of the stability field of endmember deerite is thus located at an invariant point at 250±70°C and 10+-1.5 kbar. Deerite rich in the endmember can thus appear only in environments with geothermal gradients lower than 10°C/km and at pressures higher than about 10 kbar, which is in agreement with 4 out of 5 independent P-T estimates for known occurrences. The presence of such deerite places good constraints on minimum pressure and maximum temperature conditions. From log f _{O 2}-T diagrams constructed with the same data base at different pressures, it appears that endmember deerite is, at temperatures near those of its upper stability limit, stable only over a narrow range of oxygen fugacities within the magnetite field. With decreasing temperatures, deerite becomes stable towards slightly higher oxygen fugacities but reaches the hematite field only at temperatures more than 200°C lower than the upper stability limit. This practically precludes the coexistence deerite-hematite with near-endmember deerite in natural environments.  相似文献   

Surface texture of Vesta from optical polarimetry     

T. Le Bertre  B. Zellner 《Icarus》1980,43(2):172-180

Polarimetric, photometric, and reflectance spectroscopic properties of asteroid 44 Vesta are simulated in the laboratory by a preparation of eucrite Bereba consisting oof a broad mixture of particle sizes (mainly greater than 50-μm) mixed and partially coated with particles of size 10 μm and less. Coarse grains are necessary for producing the same albedo and a very fine dust coating is necessary for producing the same polarization inversion angle as observed for Vesta. There are less small grains and fine dust in this sample than in lunar soils. Photometrically, if coating a sphere, this sample shows a constant brightness on the sunward half of the observed hemisphere, the brightness being given on the other half by the Minnaert reciprocity principle. With such a photometric behavior, the global geometric albedo and the sub-Earth point geometric albedo differ by no more than 5%. The microscopic phase coefficient β is 0.021 magnitude per degree for the sample; the larger value, β = 0.025, observed telescopically for Vesta indicates that large-scale roughness is present on this asteroid.  相似文献