共查询到20条相似文献，搜索用时 31 毫秒
1.
Ｎｕｍｅｒｉｃａｌｓｉｍｕｌａｔｉｏｎｏｆｓｅｄｉｍｅｎｔｌｉｆｔｅｄｂｙｗａｖｅｓａｎｄｔｒａｎｓｐｏｒｔｅｄｂｙｔｉｄａｌｃｕｒｒｅｎｔｓ￥ＣａｏＺｕｄｅａｎｄＷａｎｇＧｕｉｆｅｎ（ＴｉａｎｊｉｎＲｅｓｅａｒｃｈＩｎｓｔｉｔｕｔｅｏｆＷａｔｅｒＴ... 相似文献
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Seagrasses are well-known ecosystem engineers. They reduce water dynamics and sediment resuspension, and trap fine sediments. However, exceptions of this paradigm have been reported. To test whether these exceptions could be related to plant cover and environmental conditions, we investigated sediment modification under influence of seagrass presence in various annual eelgrass (Zostera marina) beds with varying plant cover and sediment composition. 相似文献
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The effect of pressure on leucine and thymidine incorporation by free-living bacteria and by bacteria attached to sinking oceanic particles 总被引：1，自引：0，他引：1
The effect of pressure on upper ocean free-living bacteria and bacteria attached to rapidly sinking particles was investigated through studying their ability to synthesize DNA and protein by measuring their rate of 3H-thymidine and 3H-leucine incorporation. Studies were carried out on samples from the NE Atlantic under the range of pressures (1–430 atm) encountered by sinking aggregates during their journey to the deep-sea bed. Thymidine and leucine incorporation rates per bacterium attached to sinking particles from 200 m were about six and ten times higher, respectively, than the free-living bacterial assemblage. The ratio of leucine incorporation rate per cell to thymidine incorporation rate per cell was significantly different between the larger attached (18.9:1) and smaller free-living (10.4:1) assemblages. The rates of leucine and thymidine incorporation decreased exponentially with increasing pressure for the free-living and linearly for attached bacteria, while there was no significant influence of pressure on cell numbers. At 100 atm leucine and thymidine incorporation rate per free-living bacterium was reduced to 73 and 20%, respectively, relative to that measured at 1 atm. Pressure of 100 atm reduced leucine and thymidine incorporation per attached bacterium to 94 and 70%, and at 200 atm these rates were reduced to 34 and 51%, respectively, relative to those measured at 1 atm. There was no significant uncoupling of thymidine and leucine incorporation for either the free-living or attached bacterial assemblages with increasing pressure, indicating that the processess of DNA and protein synthesis may be equally affected by increasing pressure. It is therefore unlikely that bacteria, originating from surface waters, attached to rapidly sinking particles play a role in particle remineralization below approximately 1000–2000 m. These results may help to explain the occurrence of relatively fresh aggregates on the deep-sea bed that still contain sufficient organic carbon to fuel the rapid growth of benthic micro-organisms; they also indicate that the effect of pressure on microbial processes may be important in oceanic biogeochemical cycles. 相似文献
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Akira Masuda 《Journal of Oceanography》1978,34(1):1-7
A variational method gives a proof that, for normal modes of Rossby waves in the ocean on a-plane with depth variable in the meridional direction, the time average of the energy flux defined as the product of the pressure and the fluid-particle velocity agrees with the time average of the energy density multiplied by the group velocity. This conclusion holds in considerably general situations and sheds light on the controversial problem of the energy transport by Rossby waves. Moreover, the variational method gives a remarkable relation between the group velocity and the phase velocity. In particular this relation shows that the absolute value of the group velocity never exceeds that of the phase velocity. 相似文献
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海洋浮游植物对硒的摄取和转化 总被引：2，自引：0，他引：2
本文研究海洋浮游植物考长过程对硒的摄取和转化。结果表明，在藻类生长初期，快速选择摄取，并积累于藻相。在指数生长期，以溶解有机物形式排出体内多余硒。在稳定生长期各形态基本趋于稳定。藻类混种培养能提高对Ｓｅ的摄取程度及溶解有机硒代谢速度。 相似文献
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Polychlorinated biphenyls (PCBs) are relict contaminants, while polybrominated diphenyl ethers (PBDEs) are in increasing use. Using sediment cores collected in the Strait of Georgia, we demonstrate that the surface sediment concentration of PCBs is largely determined by environmental processes, such as sediment accumulation and mixing rates, while that of PBDEs is strongly influenced by proximity to source. The Iona Island wastewater outfall appears to be a primary pathway for PBDEs. As well, Vancouver Harbour is highly contaminated with both classes of chemical. BDE-209, the main component of deca-BDE, is the dominant PBDE congener. Environmental debromination is not evident. Currently, the ranges of the surface concentration of PCBs and PBDEs are similar to one another, but that will change in the future, as the concentration of PBDEs continues to rise. The experience with PCBs suggests that if PBDEs were banned today, it would take decades for inorganic sediment to bury them. 相似文献
7.
基于小波变换和HIS变换的海冰SAR与光学遥感影像融合方法研究 总被引：3，自引：2，他引：1
Sea ice as a disaster has recently attracted a great deal of attention in China. Its monitoring has become a routine task for the maritime sector. Remote sensing, which depends mainly on SAR and optical sensors, has become the primary means for sea-ice research. Optical images contain abundant sea-ice multi-spectral information, whereas SAR images contain rich sea-ice texture information. If the characteristic advantages of SAR and optical images could be combined for sea-ice study, the ability of sea-ice monitoring would be improved. In this study, in accordance with the characteristics of sea-ice SAR and optical images, the transformation and fusion methods for these images were chosen. Also, a fusion method of optical and SAR images was proposed in order to improve sea-ice identification. Texture information can play an important role in sea-ice classification. Haar wavelet transformation was found to be suitable for the sea-ice SAR images, and the texture information of the sea-ice SAR image from Advanced Synthetic Aperture Radar(ASAR) loaded on ENVISAT was documented. The results of our studies showed that, the optical images in the hue-intensity-saturation(HIS) space could reflect the spectral characteristics of the sea-ice types more efficiently than in the red-green-blue(RGB) space, and the optical image from the China-Brazil Earth Resources Satellite(CBERS-02B) was transferred from the RGB space to the HIS space. The principal component analysis(PCA) method could potentially contain the maximum information of the sea-ice images by fusing the HIS and texture images. The fusion image was obtained by a PCA method, which included the advantages of both the sea-ice SAR image and the optical image. To validate the fusion method, three methods were used to evaluate the fused image, i.e., objective, subjective, and comprehensive evaluations. It was concluded that the fusion method proposed could improve the ability of image interpretation and sea-ice identification. 相似文献
8.
There is a body of literature indicating that pre-exposure to low levels of metals may increase tolerance during subsequent exposure.1 We have previously demonstrated that exposure to cadmium at 100 to 500 μg/liter will retard the rate of fin regeneration in the killifish Fundulus heteroclitus.2 These experiments were designed to investigate the effects of pre-exposure to cadmium, using fin regeneration as the parameter of effect. The results indicate that pretreatment allows this species to regenerate faster during cadmium treatment as compared to non-pretreated fish, and that the relationship between the pretreatment and treatment concentrations is relevant to pretreatment effects. 相似文献
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ＳｏｕｔｈｅｒｎＯｓｃｉｌｌａｔｉｏｎｆｏｒｃｅｄｂｙｈｅａｔｓｏｕｒｃｅａｎｄｔｏｐｏｇｒａｐｈｙＱｉａｎＷｅｉｈｏｎｇ,ＹｏｕＸｉｎｔｉａｎ（ＲｅｃｅｉｖｅｄＪｕｎｅ５,１９９６,ａｃｃｅｐｔｅｄＤｅｃｅｍｂｅｒ９,１９９６）Ａｂｓｔｒａｃｔ──... 相似文献
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用表层漂流浮标对海上溢油实时跟踪和监测的方法 总被引：1，自引：0，他引：1
一种适用于近海使用的表层漂流浮标,利用GPS定位,通过GSM/CDMA网络传输数据,是一种准确实时、成本低廉的环境监测和海流、污染跟踪工具。文章介绍几种溢油跟踪监测方法和特点、表层漂流浮标的设计及其在溢油漂移轨迹跟踪中应用的特点。 相似文献
13.
Pauline A. Nye 《新西兰海洋与淡水研究杂志》2013,47(2):243-254
Macrophthalmus hirtipes (Jacquinot, 1853) excavates burrows under water in soft, muddy sand that remains waterlogged at low tide. The crabs are immersed for at least 4 h in every tide. The burrows are usually single, blind‐ending, slightly curved passages; their openings do not appear to be deliberately closed by the crabs. Excavation is effected by using one set of walking legs as a scoop while the other set provides sideways traction. Burrow openings are readily obscured by water movement, so that apparent burrow density does not give a true indication of the number of crabs in an area, but only indicates how many have been active recently; the true density may be found by sieving. The burrowing activity of M. hirtipes is compared with that of other ocypodid crabs, and the functions of burrows are discussed. A distinction is made between excavating a burrow and rapid burying, because the two behaviours are very different, and must involve different adaptations and selection pressures. 相似文献
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地形与热源强迫下的南方涛动 总被引：1，自引：0，他引：1
用El Nino和La Nina位相时的海温异常和地形作为大气下垫面的异常强迫,引入IAP的两层原始方程大气环流模式,模拟出了南方涛动的典型结构.当去掉地形后,仅仅由海温异常也能模拟出太平洋东西部的气压异常振荡,但太平洋东部振荡中心的位置并不与观测的一致.由此可见,观测到的南方涛动是在实际地形下对全球海温异常的响应. 相似文献
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This paper presents a new bearings-only method of detecting and tracking low signal-to-noise ratio (SNR) wideband targets on a constant course and velocity trajectory. A track-before-detect strategy based on matched velocity filtering is adopted using spatial images constructed from a sequence of power bearing map (PBM) estimates accumulated during a track. To lower the threshold SNR for detection, a discrete bank of matched velocity filters integrates the PBM images over a range of hypothesized trajectories, such an approach eliminates the need to estimate the number of targets since signal detection is determined by comparing the output of each matched filter (MF) to a decision threshold. The distribution of the MF output is derived based on a single point target in diffuse noise assumption. Receiver operating characteristic curves show a definite detection gain under low SNR conditions for matched velocity filtering (track-before-detect) over detection from a single PBM 相似文献
18.
Jebali J Banni M Gerbej H Boussetta H López-Barea J Alhama J 《Marine environmental research》2008,65(4):358-363
Metallothionein was quantified in sea bass Dicentrarchus labrax intraperitoneally (i.p.) injected with different Cu, Cd and Hg doses (50-250 microg kg(-1) wet wt) after 48 h exposure. A distinct peak with 16.8 min retention time was obtained by reversed-phase high performance liquid chromatography coupled to fluorescence detection (RP-HPLC-FD) with the three metals. Total metallothionein levels assayed in unheated liver extracts by RP-HPLC-FD were significantly higher (1.3-1.95-fold) than those obtained by the well-established spectrophotometric method. In the RP-HPLC-FD method, metallothionein increased linearly with Cu and Hg doses, being saturated beyond 100 mug kg(-1) Cd. Maximum induction was obtained at 100 microg kg(-1) Cd (5.3-fold), and 250 microg kg(-1) Cu or Hg (8- and 5.1-fold, respectively). At low doses no metallothionein induction was shown by the less sensitive spectrophotometric assay. 相似文献
19.
P.S. Rainbow 《Estuarine, Coastal and Shelf Science》1985,21(5):669-686
The crab Carcinus maenas (L.) and the barnacle Elminius modestus Darwin were exposed to a range of dissolved concentrations of Zn, Cu and Cd for 21 days in artificial seawater. Accumulation of Zn and Cu by crabs has been interpreted in terms of the presence of a regulation mechanism to maintain constant body concentrations (83·2 ± 19·4 μg Zn g?1 dry wt.; 39·8 ± 9·8 μg Cu g?1 dry wt.) under varying external dissolved metal levels, until a threshold dissolved metal concentration (c. 400 μg Zn l?1; c. 170 μg Cu l?1) beyond which net accumulation of metal begins. Cadium appears to be accumulated by C. maenas at all exposures with no evidence for regulation of body cadmium concentrations. Exposure of E. modestus to Zn, Cu or Cd caused net accumulation of the respective metal in the bodies of the barnacles, with no evidence for regulation of body metal concentrations. 相似文献
20.
Fertilisation and larval metamorphosis of reef-building corals are important life history events leading to recruitment of juvenile corals to reef populations. Little is known of the sensitivity of these early life phases to pollution, or their relative susceptibility to certain toxicants compared with established coral colonies. Inhibition of fertilisation and larval metamorphosis of the coral Acropora millepora (Ehrenberg, 1834) was assessed in response to solutions of the antifoulants tributyltin (TBT) and copper (Cu) using laboratory-based bioassays. Nominal concentrations that inhibited 50% fertilisation and metamorphosis (IC50) were calculated from 4 h fertilisation and 24 h metamorphosis assays and were based on introduced dose. Cu was most potent towards fertilisation with an IC50 of 17.4 micrograms/l. TBT however, proved more toxic to larval metamorphosis having an IC50 of 2.0 micrograms/l. Inert surfaces coated with either Cu- or TBT-based antifouling paint also inhibited fertilisation and metamorphosis. The degree of inhibition was correlated with surface area of the paint coating. These results indicate fertilisation and metamorphosis of coral can be sensitive to active components of antifouling paints. 相似文献