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1.
Based on the comparative analysis of the characteristics of the early summer maxima of the normalized radiance from the satellite ocean color data, the seasonal trend of the concentration of the chlorophyll “a,” and the species composition of the phytoplankton from determinations in water samples from the Black Sea, it is concluded that the summer chlorophyll maximum is due to the coccolithophorid bloom occurring from late May to mid June in the Black Sea basin.  相似文献   

2.
-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   

3.
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4.
Diatoms are major primary producers of microbial biomass in the Antarctica. They are found in the water and sea ice. The distribution, abundance of the ice diatoms and their relation to the environmental factors inside and outside the ice have been studied for its special role in the Antarctic Ocean ecology. In this paper we describe the abundance, distribution and composition of diatom assemblages in  相似文献   

5.
Small-scale fisheries are often seen as a solution for ensuring sustainability in marine exploitation. They are viewed as a suitable alternative to industrial fisheries, particularly when considering their social and economic importance in developing countries. Here, we show that the booming small-scale fishery sector in Senegal, in the context of increasing foreign demand, has induced the collapse of one of the most emblematic West African marine fish species, a large grouper Epinephelus aeneus, historically called ‘false cod’ by European fishers. The overexploitation of this species appears to be on account of the increasing effort sustained by a growing international demand and important subsidies, which resulted in a relative stability of the average economic yield per fishing trip and an incentive for continuing targeting this species to almost extinction. It is a critical time for addressing and mitigating the pressure of the small-scale fisheries to prevent declines of fish species that are highly valued by northern markets. A balance between conservation and exploitation is necessary to maintain ecological viability while considering the socio-economic importance of the small-scale fisheries. However, a new strategy is needed for conservation that will consider and articulate simultaneously the concerns regarding unmanaged and growing small-scale fisheries, rampant subsidies and increasing foreign demand.  相似文献   

6.
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7.
On the basis of Miner's linear cumulative damage theorem, random variables are introduced to evaluate objectively the fatigue damage of a semi-submerged platform structure and a method is presented to analyze the fatigue reliability of the structure in its design life. The reliability of the method is verified through numerical examples and some conclusions are drawn, which have certain guiding and reference value for design and inspection.  相似文献   

8.
The analysis of the data of model tests of two large deep wharves and monographic experimental studies show that two aspects are to be improved so as to predict the wave uplift forces on the bottom of a circular cylinder. The first aspect is the uplift pressure distribution on the bottom, and the second is the correct determination of the phase for maximum horizontal wave forces. The second problem has been solved. Synthesizing the results of theoretical analysis and experiments, we suggest a diagram for the determination of the phase when the maximum horizontal wave force appears. On the basis-ef the diagram the simultaneous wave uplift forces can be obtained for the structural stability analysis.  相似文献   

9.
Cruise observations with CTD (conductivity-temperature-depth) profiler were carried out in the southern Taiwan Strait in the summer of 2005. Using the cruise data, two-dimensional maps of salinity and temperature distributions at depths of 5, 10, 15, 20, and 30 m were generated. The maps show a low salinity tongue sandwiched by low temperature and high salinity waters on the shallow water side and high temperature and high salinity waters on the deep water side. The further analysis indicates that the low salinity water has a nature of river-diluted water. A possible source of the diluted water is the Zhujiang (Pearl) Estuary. Meanwhile, the summer monsoon is judged as a possible driving force for this northeastward jet-like current. The coastal upwelling and the South China Sea Warm Current confine the low salinity water to flow along the central line of the strait. Previous investigations and a numerical model are used to verify that the upstream of the low salinity current is the Zhujiang Estuary. Thus, the low salinity tongue is produced by four major elements:Zhujinag Estuary diluted water, monsoon wind driving, coastal upwelling and South China Sea Warm Current modifications.  相似文献   

10.
Expansion and development of the fisheries sector was the driving force behind Iceland’s economic transformation during the 20th century. However, the role of fisheries in national and regional economies is neither well documented nor understood. National accounts do not fully reflect the significant part played by the fisheries as they do not take into consideration the various ways economic activity in the fisheries sector affects other branches of the economy. The fisheries sector, which includes fishing and fish processing, has been established as a base industry within the Icelandic economy. Using data collected during 2010 and 2011 and cluster analysis techniques, this paper seeks to establish the economic importance of the fishing industry in Iceland. As a base industry, this paper finds that a wide range of companies have gradually developed to service the sector and through these interlinkages, the fisheries sector and its related operations can be viewed as an industry cluster.  相似文献   

11.
The Svalbard Fisheries Protection Zone is an international institution on the brink of being challenged in a critical phase of being institutionalized as a Norwegian property regime. The potential disturbance comes from the zooplankton redfeed, a new and valuable resource harvestable within the zone. Though the pressures on Norway’s inspection routines in the zone are challenged at times, this article suggests that the zone as a management regime is a surprisingly robust institution still. Nevertheless, in such a critical phase it is important not to allow possible exogenous shocks to appear, and creating a separate redfeed regime for the plankton will allow the Norwegian government to bypass this possible disturbance and allow for continued solidification of the zone into an EEZ for Norway.  相似文献   

12.
The planar photosynthetically available radiation (PAR), turbidity and concentration of chlorophyll a (chl a), were measured at 26 stations in the Huanghai (Yellow) Sea during a cruise of China SOLAS from 19 to 27 March 2005. Due to low chl a (<0.35 mg · m-3 ) in upper layers (above 5 m), suspended particulate matter became the major factor that influenced the turbidity in early spring. The calculated vertical diffuse attenuation coefficient of PAR, K PAR , varied with water depths with a maximum value in t...  相似文献   

13.
INTRODUCTIONThe coast zone is the area where most human activities take place and where the highest economic benefit is produced. The knowledge of the distribution and variation of primary production provides the bases as reference helping the marine exploitation and management.  相似文献   

14.
Subterranean estuaries, i.e., the mixing zone between terrestrial groundwater and recirculated seawater, host a wide range of microbiota. Here, field campaigns were conducted at the mouth of the subterranean estuary at the Sanggou Bay(Shandong Province, China) over four consecutive seasons at a seepage face(0-20 cm depth). The diversity of benthic microbiome was characterized via 16S rRNA gene sequencing and metagenomics, combined with physic-chemical parameters, e.g., organic carbon, total nitr...  相似文献   

15.
A comparative study using fluorometry on 6 types of filters for the determination ofChl a in seawater was carried out. The results show that whatman GF/C glass fiber filterwith a layer of MgCO_3 is the best among them. The values of Chl a obtained by thisway were not only higher, but transparency of extracts was also better than that by otherfilters. The sensitivity of fluorometry was much higher than that of spectrophotometry, sothat only small amount of seawater was enough. Furthermore, the grinding and centrifuga-tion can be eliminated, so the procedure is much simplified and is suitable to be used onboard ship.  相似文献   

16.
In this paper,the maneuvering characteristics of a low speed submersible are investigated.First,the captive model tests are carried out to obtain the hydrodynamic forces acting on the submersibleusing a Planar Motion Mechanism(PMM).For the hydrodynamic forces within a wide range of attack an-gles,the hydrodynamic coefficients which are usually used in the conventional maneuvering motion arequite difficult to be applied.In this case,a Fourier series is adopted to represent the hydrodynamic forcesand it fits the experimental data well.Then,based on the experimental results the simulation calculationsare made to predict some of the maneuvering performance of the low speed submersible.  相似文献   

17.
V. V. Povazhnyi 《Oceanology》2014,54(3):387-391
A simple fluorometer for determination of the chlorophyll “a” (chl “a”) concentration in an extract based on bright light emitting diodes (LEDs) in the blue and IR spectrum range used as a continuous excitation light source and light detector, respectively, has been described. Results of calibration and validation of the system’s signal with the help of extracts with different chl “a” concentrations are presented.  相似文献   

18.
Izvestiya, Atmospheric and Oceanic Physics - The evolution of the distribution pattern of an ink droplet freely falling on the wavy surface of a liquid is traced by video-recording methods. A...  相似文献   

19.
The mesoscale dynamics of the Scottish side of the Faroe–Shetland Channel have been investigated using synoptic in situ and remote sensing observations. A cold core cyclonic eddy, identified from an AVHRR image, had a diameter of about 50 km and surface current speeds of up to 50 cm s-1; it appeared to be attached to the 800 m isobath as it moved north-eastward along the edge of the channel at about 8 cm s-1. Speeds in the slope current were about 50 cm s-1 but increased to 70 cm s-1 where the current was compressed by the eddy. Offshore, over the 1000 m isobath in the cooler water, speeds in the current were slower (ca. 20 cm s-1). North-west of the Shetlands the offshore edge of the slope current was deflected across the channel for a distance of about 70 km from the shelf edge. The speed of drifters in the slope current increased to over 60 cm s-1 as they moved anti-cyclonically around this deflection. CTD profiles suggest that the movement of the surface waters was mirrored in the deep water of the channel. The deflection carried a very large quantity of North Atlantic Water into the central part of the channel; its cause and ultimate fate are not known, although it is likely to have had a significant impact on the dynamics of the channel.  相似文献   

20.
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   

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