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1.
The pre-Cretaceous basin evolution of the Feda Graben area in the vicinity of the Norwegian-Danish basin has been reconstructed utilizing geological and structural interpretation. The analysis reveals that the basin was faulted at its borders prior to the salt deposition in the Late Permian. Salt movement was initiated in Late Triassic and thick Triassic and Lower Jurassic pods were deposited in the graben area due to this movement. Salt pillows were developing along the Feda Graben bordering faults until Middle Jurassic when the pillows were collapsed. Salt diapirs within the study area preferentially occupy the crest of the Feda Graben and their occurrence is controlled by the underlying faulted topography. The diapirs were fed by salt from the central and southern parts of the basin and were developed by different processes i.e. upbuilding, downbuilding. Various raft structures were developed in the graben area hanging wall while some uplift occurred in the footwall during Mesozoic rifting. The Feda Graben area experienced rifting from Late Jurassic to Early Cretaceous. The most pronounced subsidence episode related with this rifting in the Feda Graben area took place along the eastern bounding Gert Fault. The Mesozoic rifting event is marked by a major unconformity on the seismic sections throughout the study area. Furthermore, the region experienced basin inversion in Late Cretaceous. The effects of inversion are more pronounced in the western part and along the Gert Fault. The inversion phenomenon can be properly understood only when considered together with the geometry of the Late Jurassic half-graben. Due to some inconsistencies in the previously proposed models for the development of the Feda Graben, a new conceptual model has been constructed.  相似文献   

2.
Dynamics of picoplankton in the Nansha Islands area of the South China Sea   总被引:5,自引:0,他引:5  
Dynamics of major picoplankton groups, Synechococcus (Syn), Prochlorococcus (Pro), picoeukaryotes (Euk) and heterotrophic bacteria (Bact) was investigated by flow cytometry for the first time in the Nansha Islands area in the South China Sea. Averaged over the whole investigation area, depth-weighted integrated cell abundance (DWA) of Syn, Pro, Euk and Bact was 1.6 (0.4-5.7)×103, 5.4 (0.1-7.3)×104, 0.7 (0.2-2.2)×103, and 2.3 (1.4-3.2)×105 cells/mL respectively. Picoautotrophic cell abundance was low in the northwest part of the Nansha Islands where surface water temperature was low and the upper mixed layer was shallow. Concurrently, a surface maximum vertical distribution pattern was observed in this area. While in the southeast and east zones where temperatures were relatively higher and nitraclines were deeper, picoplankton is abundant and a subsurface maximum around 50-75 m is observed. Coupling of horizontal and vertical distribution patterns of picoplankton abundance and hydrological status wa  相似文献   

3.
In this paper, a detailed statistical analysis of the wind and wave fields in the Indian Ocean (IO) for the period of 1998-2009 was performed based on using the wind fields taken from the site of the National Centers for Environmental Prediction and the National Oceanic and Atmospheric Administration (NCEP/NOAA) [1] and on the numerical wind-wave model WAM [2] modified with the source function proposed in [3]. The primary analysis of the fields includes mapping the wind and wave fields, as well as their energy fields, calculated with different scales of space-time averaging; the subsequent zoning of the IO area; and assessing the seasonal interannual variability of all the fields and their 12-years trends. Further analysis is carried out taking into account the zoning. This analysis includes a construction of the time series obtained with different scales of space-time averaging for all the fields, a spectral analysis of these series, finding and analyzing the spatial and temporal distribution of extrema of the wind and wave fields (accounting for the their sharing in the zones), and making histograms of the wind and wave fields and calculating their first four statistical moments (in the zones and in the ocean as a whole). The results allow us to evaluate a large set of statistical characteristics of the wind and wave fields in the IO area, scales of their variability, their long-term trends, and the features of distribution for these statistical characteristics in the ocean area as well.  相似文献   

4.
The reasons why most small-rights holders do not participate in management of the fishery for small pelagic fish (‘small pelagics’) in South Africa, despite legislation and policy encouraging their participation, were analysed. Membership of the Small Pelagics Management Working Group (SPMWG), the main participatory governance organ, is limited to representatives of recognised stakeholder associations. Rights holders therefore have to belong to a stakeholder association, which then selects a member or members to represent them on the SPMWG. Small quotas and the difficulties of sourcing capital mean that small-rights holders are not able to invest in infrastructure. Besides, most of the small-rights holders and their companies lack experience and management skills to survive independently in this highly competitive industry, which is based on high volume and low profit margins. As a result, most of the small-rights holders have no option but to enter into complex catching and processing agreements with vessel- and factory owners belonging to the existing recognised stakeholder associations. For the small-rights holders, it does not make sense to join these associations or even to form their own if they cannot actively participate in the industry independently. Greater participation by small-rights holders should start with their genuine integration into the industry through improved ability to invest in infrastructure and through management skills development. Most likely, this will require an interventionist approach by government.  相似文献   

5.
The materials were obtained from the survey conducted in the Kuroshio area of the East China Sea to the Southwest of Kyushu in Japan (29°30'-32°00', 128°00'-130°'00'E) on board the R. V. Yoko Maru of Seikai Regional Fisheries Lab, Fisheries Agency, Japan in June 15~28, 1988 during China-Japan Joint Research on the Kuroshio. Zoo-plankton was collected by means of the North Pacific Net with model TSK flowmeter through vertical haul from 50 -Om. Temperature and salinity were measured with CTD. 134 species (including 4 spp. ) of planktonic copepods were preliminarily identified in the survey area. Most of them belonged to the tropical and subtropical species and a few of them were the warm-temperate species and eurytopic species. The main dominant species vteieOncaea venusta, Oithona plumifera, Clausocalanus furcatus, C. Arcuicornis, Paracaianus dculeatus, Oithona similis, Temara turbinata, Oncaea media, Undinula danvinii, Acartia negligent, Corycaeus speciosus, Scolecithrix danae, etc. The total number  相似文献   

6.
Variations of monsoon wind field in the sea area along the southeastern coast of China during the ENSO events and its influence on the sea level and sea surface temperature (SST) are explored mainly on the basis of the data of monthly mean wind at 850 hPa and five coastal stations during 1973-1987. The results from the analyses of the data and theoretical estimation show that the southwest wind anomalies appeared in the study area during the events, and northeast wind anomalies occurred in general before the events. With the coastline of the area being parallel basically to the direction of the wind, an Ekman transport will result in an accumulation of the water near the coast or a departure of the water from the coast. As a result , the sea level and SST there will be affected markedly. During the events, southwest wind will intensify in the summer, and northeast wind will weaken in the winter. Their total effect is that a large negative anomaly of the sea level and SST will occur. The estimations indi  相似文献   

7.
Effective species management requires good knowledge on vessel dynamics, either at a stock basis or through the establishment of multiannual management plans as advisable under the new European Common Fisheries Policy (CFP). Achieving such knowledge on Portuguese multi-gear fisheries is challenging given the large number of species caught and the different management measures applied to potential target species. The latter ranges from no input or output controls to output controls based on individual vessel quotas (IVQ). To provide accurate regional knowledge to the CFP, the dynamics of vessels involved in the trammel net fishery targeting anglerfish (Lophius spp.) was characterised based on onboard sampling data and logbook reports. The selected vessels were very dynamic, and were found to target other species such as hake (Merluccius merluccius), John Dory (Zeus faber) and octopus (Octopus vulgaris). Anglerfish landing trends can be explained by changes in abundance, quota availability and shifts/changes in fishing effort. Overall, the dynamics of these vessels varied with area of exploitation, IVQ value and anglerfish total allowable catch (TAC). These results show the influence of different management systems in the dynamics of vessels and the advantage of an IVQ management system, where fishers can spatially and temporally allocate effort. Results also highlight a fishing effort shift towards unregulated species in face of IVQ or TAC restrictions.  相似文献   

8.
Most of the hydrocarbon fields in the oceanic and thinned suboceanic crust are associated with deep-seated faults. This fact might be caused by methane formation under the serpentinization of the upper mantle rocks and its transfer to the sedimentary cover with hydrotherms. The northern part of the Indian Ocean deformation zone may be of considerable promise for the formation of deposits of such genesis. This is favored by the occurrence of the long-living hydrothermal activity over the deep-seated faults and by quite the thick sedimentary cover (over 1 km). In the course of cruise 32 of the R/V Akademik Kurchatov, a buried anticline formation with an acoustic anomaly of the bright-spot type was discovered 450 km southwards from Sri Lanka Island. This may point to the presence of a hydrocarbon accumulation in the sedimentary cover.  相似文献   

9.
Seismic studies offshore southern Chile have revealed the presence of a 70–80 km wide accretionary prism seaward of the Golfo de Penas (GPAP), where the Chile Ridge collided with the South American Plate between 3 and 6 Ma ago. Using the paleo-positions of the Chile Ridge relative to South America, the maximum age of this accretionary prism, which continues to be formed in the aftermath of the ridge–continent collision, has been estimated. Building on these earlier findings, this study presents a mass balance analysis based on a 2D model of accretionary wedge and trench geometry. This model can explain the relative importance of sedimentary fluxes and deformation front migration for the wedge restoration. The proposed model can also serve to evaluate the effects of fluctuations in (1) terrigenous sediment flux related to climate change, and (2) subduction channel thickness on the accretionary prism growth. Notably, the data reveal that the key parameters controlling the rebuilding of the GPAP are the terrigenous sediment flux (75 km2/106 years), the relative advance of the deformation front (39.6 km/106 years), and the thickness of the subduction channel (0.1 km). Moreover, the range of possible solutions for the observed size of the accretionary prism is narrowed by fitting the present-day thickness of sediments at the deformation front. Finally, climate-induced variations in sedimentary fluxes on the margin can affect the rate of growth of the accretionary prism during short periods of time (<100,000 years).  相似文献   

10.
-Wave refraction-diffraction due to a large ocean structure and topography in the presence of a 'current are studied numerically. The mathematical model is the mild-slope equation developed by Kirby (1984). This equation is solved using a finite and boundary element method. The physical domain is devid-ed into two regions: a slowly varying topography region and a constant water depth region. For waves propagating in the constant water depth region, without current interfering, the mild- slope equation is then reduced to the Helmholtz equation which is solved by boundary element method. In varying topography region, this equation will be solved by finite element method. Conservation of mass and energy flux of the fluid between these two regions is required for composition of these two numerical methods. The numerical scheme proposed here is capable of dealing with water wave problems of different water depths with the main characters of these two methods.  相似文献   

11.
Hepatitis A virus (HAV) is very persistent in the environment and is especially difficult to detect in the seafoods. In recent years, molecular cloning of the genome of HAV has led to sensitive polymerase chain reaction (PCR) method for the detection of HAV RNA. Here we describe a new and simple procedure to extract RNA from contaminated clams and the PCR method for detection of HAV in environmental samples. The specificity and efficiency of PCR amplification were studied using cDNA and RNA of HAV. Three primer couples gave satisfactory results. Some basic parameters of the PCR were modified to perform a highly specific and sensitive test.  相似文献   

12.
-Investigations of Chi, a and primary production were carried out in the coastal upwelling area (27°'-30°30'N, west to 124°00'E) off Zhejiang in August and October 1981. The high-value areas of Chl. a were in nearshore waters and on top of the upwelling front, where Chl. a occurred the maximum 7.40 mg/m3. With the average of 1.25 g C/m2.d, the primary production was more than 2.0gC/m2·d incenteral area of the upwelling, and the whole surveyed area's output was about 4.4 ×104 tons C/d.  相似文献   

13.
In the first part of the present paper we have explained why we manage to formulate another wave prediction model when so many of them, including the so-called third generation model, have already been in use. The wind-wave part of the proposed model has also been given. Now we proceed to discuss the swell part,the implementation of the model as a prediction method,mumerical experiments done with ideal wind fields and hindcasts made in the Bohai Sea,in the neighboring seas adjacent to China and in the Northwest Pacific.  相似文献   

14.
P-glycoprotein (pgp), an efflux transporter localized in a variety of tissues including the intestinal mucosa, renal tubules and bile canaliculi, is known to participate in the disposition of a variety of chemicals, including steroid hormones. This study examined the relationship of pgp to the movement into the bile of the hormone estradiol (E2), and the potential for transport interactions between the environmental pollutant nonylphenol ethoxylate (NPE) and E2. Biliary-cannulated in situ-prepared isolated perfused livers were used to assess pgp transport function. E2, in competitive transport preparations with Rhodamine 123 (Rho123), a pgp substrate, demonstrated significant decreases in Rho123 transport into bile, as did the prototypic inhibitor and substrate verapamil. [3H]E2 (0.28 nM) transport into bile was significantly reduced with either 20 M NPE or verapamil. These results suggest that E2 is a substrate and/or modulator for the catfish biliary pgp transporter, and that NPE potentially influences biliary transport and excretion of E2.  相似文献   

15.
Pile foundations that support transmission towers or offshore structures are dominantly subjected to cyclic lateral load induced by wind and waves. For a successful design, it is crucial to investigate the effect of cyclic lateral loads on the pile behavior that is loaded laterally. Although the py curve method is generally utilized to design the cyclic laterally loaded pile foundations, the effect of cyclic lateral loads on the pile has not been properly implemented with the py curve. This reflects a lack of consideration of the overall stiffness change in soil–pile interaction. To address this, a series of model pile tests were conducted in this study on a preinstalled aluminum flexible pile under various sandy soil conditions. The test results were used to investigate the effect of cyclic lateral loads on the py behavior. The cyclic py curve, which properly takes into account this effect, was developed as a hyperbolic function. Pseudo-static analysis was also conducted with the proposed cyclic py curve, which showed that it was able to properly simulate cyclic laterally loaded pile behavior in sandy soil.  相似文献   

16.
The Magnuson-Stevens Fishery Conservation and Management Act (1976), opened a new era of federal fishery management in the United States. It was enacted primarily to establish a system for conserving and managing fisheries in the new 200-mile (EEZ). The US assumed exclusive authority for managing all fisheries within the EEZ, except for highly migratory species such as tunas and billfishes. Within the framework of the Act, eight Regional Fishery Management Councils (Regional Councils) were created, which are responsible for preparing Fisheries Management Plans (FMPs) in federal waters under their jurisdiction. Each FMP must meet a series of National Standards (NSs) for conservation and management. The Act was reauthorized in 1996 with the passage of the Sustainable Fisheries Act (SFA), which aimed at fine tuning the fishery regulatory apparatus that was established under the original Act. This "fine tuning" involved increased attention to biological concerns, and removal of ambiguities within it. The Act was reauthorized again in 2007, mainly to provide for more clear directives and regulations to end overfishing. After more than thirty years since the Act was passed into law, the debate among conservationists, commercial and recreational fishery representatives, and politicians on the effectiveness of the Act in achieving its purported goals it still continues. Is the Act delivering on its promises? Do NSs reflect the most important priorities for the US fishery resources, conservation and sustainable exploitation? Do the Regional Councils represent all parties that should be involved in the fisheries resources management? The aim of this paper is to provide a critical analysis to answer these questions. This paper begins with a review of the Act and its background, followed by discussion and analysis of the Act's benefits and flaws. Finally, suggestions for the implementation of its structure and future directions in fishery management strategies are made.  相似文献   

17.
We realize the algorithm of adaptive statistics of forecasting errors for the assimilation of the climatic fields of temperature and salinity in the σ-coordinate model of the dynamics of the Black Sea. The principal relations of this algorithm and its simplified version based on the Kalman filter are presented. The distinctive features of realization of the algorithm specified by the model are discussed. We also present the results of comparison of the hydrophysical fields of the Black Sea reconstructed according to the algorithm of adaptive statistics and a simplified scheme of assimilation of the climatic data. It is shown that the dependence of sources in the transport equations (heat and salt diffusion) on the four-dimensional variances of forecasting errors and threedimensional measurement errors enables one to reconstruct the mutually adapted climatic parameters of the sea more exactly.  相似文献   

18.
Before the mid-1990s, Apo Island, Philippines, was often described as one of the world's best examples of community-based marine management. This paper studies the less-documented transition of the island during the late 1990s from community-based management to centralised national state management. Extensive interviewing of islanders has revealed deep misgivings about the centralised regime—the Protected Area Management Board (PAMB). PAMB's aim of implementing the National Integrated Protected Areas Systems (NIPAS) Act was initially looked upon favourably by islanders, but it has lost that support because of its exclusion of stakeholders from management and its poor institutional performance. The paper's conclusion is that the implementation of the NIPAS Act highlights the limitations of top-down management, and that there is a need to restore an element of local stakeholder participation in the governance of Apo's marine protected area (MPA). A system of co-management between community and national state actors is essential to ensure the long-term sustainability of Apo's marine resources.  相似文献   

19.
lwnoowrlowIt is a hot spot in the world to carry out palcoocean and paleo-climate studies by using sur-face sediments. One of the direct effects of the global clirnate changes or short Periedic abnor-mal clirnate events is the variety of sea surface temPerature (wr). Increase or deCrease of theSST wil1 have certainly imPact, the unsaturate ratio (U)v) of long-chain alkenones (LCA)compe Of planktonic algae. The ratio Ulv records the information of SST changes, whichwill be entirely and or…  相似文献   

20.
This paper examines disposal of metals and the origin, characteristics, and distribution of sedimentary organic matter (SOM) in a Mediterranean karstic estuary in the north-eastern Adriatic. This environment offers a real-time, small model system for studies of geochemical processes in microtidal Mediterranean estuaries that are infilling with sediments and classified as river-dominated disequilibrium estuaries. The results have shown that the longitudinal distribution of heavy metals in sediments follows the sedimentation dynamics and deposition pattern of river-borne, clay mineral particles. The highest concentration of metals was found in the restricted upper part of the estuary, characterized by rapid deposition of clay particles and terrestrial sedimentary organic matter, and decreases toward the open sea. The vertical distribution of metals in sediment cores depends on the prevailing pH and Eh conditions. Significant increases of the concentrations of metals in the uppermost strata are the result of recent anthropogenic inputs. The share of the terrestrial component in SOM, estimated by N/Corg atomic ratios and δ13C values, decreases with distance from the river mouth. The small vertical variation in δ13C values of SOM indicates that a fast sedimentation rate overrides the diagenetically determined decomposition. The results obtained indicate that river-borne inorganic particles, natural terrigenous organic material, and anthropogenic metal loads are trapped in sediments of the estuarine system. Under the prevailing conditions, there is negligible transport towards the open sea.  相似文献   

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