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71.
A spread of warm water from the first crest of the Kuroshio Extension is periodically enhanced by northward warm water intrusions from the main current. The water type in the spread area was previously found to be the same as that in the Kuroshio front at depth. In looking for the possible mechanism responsible for the northward warm water intrusions, a dynamic analysis in the Kuroshio front was carried out by using CTD, ADCP, AVHRR and ARGOS buoy data, obtained in 1996 by the R.V. Hakuho Maru. Downstream, cross-stream and vertical velocities in the Kuroshio Extension were found by using a "stream coordinate system". The velocity field in the Kuroshio front at the first crest showed a double structure with two surface velocity maxima. In the inner part of the front, relatively high cross-stream (northward) and vertical (upward) velocities were found. Thus, this study suggests that while water particles flow downstream along the first stationary meander of the Kuroshio Extension, they also experience lateral and vertical movements which allow the deeper water from an upstream location to rise to the surface layer, and in certain locations to deflect northward. By assuming isopycnal movement and conservation of potential vorticity, it was found that in those locations where anticyclonic curvature of the meander increases, warm water is more likely to deflect northward. High ageostrophic components observed in the first 300 m of the water column are probably related to the relatively high cross-stream and vertical velocities in the inner part of the front. 相似文献
72.
Baraza J. Ercilla G. Farrán M. Casamor J. L. Sorribas J. Flores J. A. Sierro F. Wersteeg W. 《Marine Geophysical Researches》1997,19(2):115-135
Multibeam bathymetric and ultra high-resolution seismic data reveal that the distal course of the Equatorial Atlantic Mid-Ocean Channel (EAMOC) extends further east and south than was previously known, and is controlled by the presence of morphologic highs related to the Fernando de Noronha Fracture Zone. Distal course of the EAMOC is buried by sediments, and does not have bathymetric expression on the seafloor. The channel fill consists of three seismic sequences, suggesting that the recent geological evolution of the channel is composed of successive phases of decreasing sedimentary activity that finally resulted in its complete burial. Tectonic and volcanic activity related to the Fernando de Noronha Fracture Zone and Ridge, together with the effect of strong pulses of the Antarctic bottom water current during the upper Pliocene are suggested to have contributed to the progressive burial and the final abandonment of the EAMOC. 相似文献
73.
采用水生毒理学方法以及通过分析蒽对 2种海洋微藻的几种生理生化指标的影响 ,初步研究了蒽胁迫对 2种海洋微藻的毒性效应。结果表明 :随着蒽浓度的不断增大 ,1 2种海洋微藻的相对增长率逐渐降低 ,叶绿素 a和类胡萝卜素含量稍有下降 ,蒽对小新月菱形藻生长的 72 h· EC50为 2 51μg· L-1 ,蒽对亚心形扁藻生长的 72 h· EC50 为 387μg· L-1 ;2还原型谷胱甘肽 (GSH)含量逐渐降低 ;3加入外源性抗氧化剂 (GSH和甘露醇 )可缓解蒽胁迫所造成的 2种海洋微藻的细胞密度的降低 ,即可缓解蒽胁迫对微藻的毒害作用 相似文献
74.
Detailed structural interpretation of the recently acquired deep seismic multichannel profiles along the Iberian Atlantic Margins (IAM Project) provides new results on the geodynamic evolution of the eastern part of the Azores-Gibraltar plate boundary. Thrusting and folding of the oceanic basement and of Mesozoic and Cenozoic sedimentary cover of the Gorringe Bank region are consistent with the N–S convergence of Iberia and Africa. Compressive structures in the Gorringe Bank region are spread over a wide area. Deformation under compression took place mainly in Tertiary times, as is evidenced by a basal unconformity and several discontinuities in Tertiary sediments, although some deformation has also been recorded in Quaternary sediments. The compressive structures in the Gulf of Cadiz are E–W oriented thrusts, folds and related diapiric structures. N–S oriented transpressive deformation is likely to occur in the western Portuguese platform. There is no continuity of structures from the oceanic to the continental domain, suggesting that deformation transfers from one side to the other through a transcurrent fault zone. The fault contact between the two domains is located in the ocean-continent transition zone. 相似文献
75.
Whether or not there are extensional detachment faults in the Alboran basement can be tested directly because a part of the Alboran Basin is now emerged. These detachments, related to crustal thinning beneath the Alboran Basin, occurred from the Aquitanian to Tortonian. The resulting extensional geometries can be described in general terms. During the Serravalian a considerable southwest extension of the basin took place, accompanied by south-southeast extension in the northern Gibraltar Arc. Other detachments affected by Serravalian extension can be found. The spreading of the Alboran was nearly coeval with roughly westward migration of the Gibraltar mountain front. 相似文献
76.
Distribution of dissolved species and suspended particulate copper in an intertidal ecosystem affected by copper mine tailings in Northern Chile 总被引:1,自引:0,他引:1
The coastline near Chañaral in Northern Chile is one of the most highly Cu-contaminated zones in the world due to discharges from mining activities for more than 60 years. The speciation of Cu has been studied to determine the importance of organic complexation in highly contaminated areas, and to assess the likely physiological impacts of Cu on marine organisms. Dissolved Cu concentrations of up to 500 nM were measured, completely saturating organic ligands and leading to free Cu2+ concentrations in excess of 10− 8 M. These values are higher than those reported in any other marine environment, and because they occur over an extensive area, provide a unique opportunity to study the effects of Cu on marine ecosystems and to see how Cu behaves when its speciation is predominantly inorganic. We found strong gradients in free Cu2+ between Chañaral and adjacent areas with lower Cu, where speciation is dominated by organic complexation. There is also a significant increase in the partitioning of Cu onto suspended particles in the contaminated areas, consistent with previous studies that showed that organic ligands stabilize Cu in the dissolved phase, whilst “excess” Cu is rapidly scavenged. Those high dissolved Cu concentrations persist in spite of solid phase partitioning and advective processes along this open-ocean coastline, suggesting that Cu inputs into the system are still very large. Measurements were made using anodic stripping voltammetry with a thin mercury film coated with Nafion, which previous workers have shown can mitigate ambiguity in the data arising from inadvertent reduction of organic complexes. Our findings suggest that this is a useful methodology for contaminated systems. 相似文献
77.
I. Brandariz P. Castro M. Montes F. Penedo M.E. Sastre de Vicente 《Marine Chemistry》2006,102(3-4):291-299
Acid–base equilibrium constants of triethanolamine (TEA) have been determined by potentiometric titrations with a glass electrode, at 25 °C. Ionic strength was kept constant with only one electrolyte (using one of these salts: NaCl, KCl, MgCl2 or CaCl2), with binary mixtures of MgCl2 and CaCl2, and finally, in a solution with a composition approximately similar to that of natural seawater without sulfate. Equilibrium constants have been expressed in function of ionic strength by means of Pitzer equations and interaction parameters proposed in this theory have been obtained. It has been found that acid–base behaviour of TEA depends greatly on the salt used: basicity of TEA is decreased by CaCl2, while it is increased by the other electrolytes used in this work. 相似文献
78.
从1999年至2002年在中国南方沿海许多养殖场的杂色鲍(Haliotis diversicolor Reeve)出现了严重的疾病,该病可感染各种规格的鲍,死亡很快,死亡率高。病鲍的外观症状表现为外套膜收缩,腹足表面变黑,肌肉变得僵硬。通过电镜观察,在肝胰腺、外套膜、肾、鳃及肠等组织中发现了一种球状病毒。病毒粒子大小为100~130nm。该病毒一般存在于间质细胞的细胞质中,为双层质膜所包裹。染病鲍细胞器如滑面内质网扩张、线粒体崩解,糖原粒、核糖体减少,核膜松疏、溶解、消失,核质边缘化。病毒的病原性通过对健康鲍的感染试验得到证实。 相似文献
79.
80.
Abstract. We describe the basic ecology of two key-hole limpets, Fissurella crassa and Fissurella limbata , which are heavily harvested by coastal shellfishermen (mariscadores) at the rocky intertidal of central Chile. The ecological role of human predation on these species was assessed. Anthropic exclusion from a stretch of the rocky intertidal at Las Cruces (non-harvested area) for about two and a half years resulted in changes of the densities and size distributions of these fissurelid species as compared to populations in control zones (harvested area). Differential human predation generates, on key-hole limpets, responses of different intensities related to the accessibility of man to the mesohabitats (sheltered platforms, exposed platforms and vertical walls) and fringes of the intertidal (mid-low intertidal and Lessonia nigrescens fringe). Thus, size distributions and mean densities of both fissurelids differ widely between the harvested and non-harvested areas on both platform habitats but not on vertical walls. In the mid-low intertidal fringe, differences are greater than in the less accessible L. nigrescens intertidal fringe. Moreover, we discuss the way in which other species, directly harvested by mariscadores (i. e., the mollusc Concholepas concholepas) can affect the keyhole limpet populations of central Chile rocky shores. Finally, we highlight the ecological role of these limpets on the dynamics of intertidal ecosystems and how they can modify community landscape. 相似文献