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101.
《Deep Sea Research Part I: Oceanographic Research Papers》2006,53(2):215-222
The exclusively deep-sea ascidian family Octacnemidae comprises several genera in which the oral siphon has hypertrophied to form two large lips which create an “oral hood” capable of capturing motile prey. Megalodicopia hians is typical of this carnivorous family and has been reported to prey upon small epibenthic crustaceans. Distribution of M. hians in the Monterey Canyon system (36°45′N, 122°00′W) (California) was determined with remotely operated vehicles. M. hians was found sparsely to depths of at least 3800 m throughout the canyon; however, abundance was greatest within the oxygen-minimum zone (400–800 m). Eggs, sperm, and recently fertilized embryos were obtained repeatedly from adults returned to the laboratory in vivo, indicating that this species free-spawns routinely. Overall egg diameter (ovum plus chorion, plus follicle cells) was 175–190 μm—considerably smaller than previously reported for this species. Embryonic development at temperature and oxygen concentrations equivalent to the oxygen-minimum zone was 2–4 d and, embryos gave rise to typical phlebobranch “simple” tadpole larvae. Larval period was extremely variable, and settlement/metamorphosis occurred up to 3 months post-hatching. These results are discussed within the context of settlement-site selection and fertilization ecology of the species. 相似文献
102.
秋季黄海中南部鱼类群落对饵料生物的摄食量 总被引:8,自引:0,他引:8
研究鱼类与饵料生物之间食物定量关系进而为多鱼种资源评估提供依据,2000~2002年秋季(10~11月)在黄海中南部海域进行了定点底拖网调查,应用Eggers模型,计算了带鱼(Trichiurus lepturus)、小黄鱼(Pseudosciaena polyactis)、黄(Lophius litulon)、细纹狮子鱼(Liparis tanakae)等23种鱼类在秋季对饵料生物的摄食量。结果表明:黄海中南部23种鱼类在秋季对饵料生物的总摄食量约为309万t,其中,鱼(Engraulis japonicus)的摄食量最高(在250万t以上),占总摄食量的80.9%。中上层和底层鱼类对饵料生物的摄食量分别为262万t和47万t左右,占总摄食量的84.7%和15.3%,鱼和细纹狮子鱼分别是中上层和底层鱼类中最主要的捕食者。磷虾类是中上层鱼类最主要的食物来源,其次是桡足类、端足类和毛颚类;虾类和鱼类是底层鱼类最主要的食物来源,其次是磷虾类。太平洋磷虾(Euphausia pacifica)、中华哲水蚤(Calanus sinicus)、细长脚虫戎(Themisto gracilipes)、脊腹褐虾(Crangon affinis)和鱼同时是黄海中南部被摄食量最高的5种饵料生物,它们被摄食的生物量之和约为233万t,占总摄食量的75.5%。 相似文献
103.
以p-硝基苯酚-β-D-氨基葡萄糖苷(pNP-NAG)为底物,研究产物类似物:p-羧基苯酚和苯酚对青蟹N-乙酰-β-D-氨基葡萄糖苷酶(NAGase,Ec3.2.1.52)活力的影响.结果表明:p-羧基苯酚和苯酚对该酶有抑制的作用,IC50分别为20.0和100.0mmol/dm^3.p-羧基苯酚和苯酚对酶的抑制均表现为竞争性类型,其抑制常数K1分别为5.03和25.67mmol/dm^3.结合产物N-乙酰-β-D-氨基葡萄糖(NAG)抑制作用表现为反竞争性类型,判断NAGase水解pNP-NAG反应为有序双双反应(Ordered Bi Bi). 相似文献
104.
We use a synthetic data experiment to assess the accuracy of ocean tides estimated from satellite altimetry data, with emphasis on the impact of the phase-locked internal tide, which has a surface expression of several centimeters near its sites of genesis. Previous tidal estimates have regarded this signal as a random measurement error; however, it is deterministic and not scale-separated from the barotropic (surface) tide around complex bathymetric features. The synthetic data experiments show that the internal tide has a negligible impact on the barotropic tidal fields inferred under these circumstances, and the barotropic dissipation (a quadratic functional of the tidal fields) is in good agreement with the energetics of the three-dimensional regional primitive equations model which is the source of the synthetic data. 相似文献
105.
以中华齿米虾(Neocaridina denticulata sinensis)基因组DNA为模板,根据胰蛋白酶基因保守序列设计简并引物,利用PCR技术获得一个基因。序列分析表明此基因与已报道的凡纳滨对虾(Litopenaeus vannamei)胰蛋白酶基因有较高的相似度,序列中包含一个内含子和两个不完整的外显子,编码182个氨基酸残基。该氨基酸序列与凡纳滨对虾胰蛋白酶氨基酸序列的相似度为83.5%;含有胰蛋白酶所特有的His、Asp和Ser组成的活性三联体、决定胰蛋白酶底物专一性的Asp、底物结合部位的G1y残基。综合分析认定该基因为胰蛋白酶基因片断。将其氨基酸序列与报道的其他动物胰蛋白酶氨基酸序列进行了系统进化分析。系统进化分析的结果与现有以表型特征为依据的虾分类结果是一致的。 相似文献
106.
Cheng-Chien Liu Richard L. Miller Kendall L. Carder Zhongping Lee Eurico J. D’Sa James E. Ivey 《Journal of Oceanography》2006,62(3):235-248
We present a new approach that incorporates two models to estimate the underwater light field from remote sensing of ocean
color. The first employs a series of analytical, semi-analytical, and empirical algorithms to retrieve the spectrum of inherent
optical properties (IOPs), including the absorption and the backscatter coefficients, from the spectrum of remote sensing
reflectance. The second model computes the profile of photosynthetically available radiation E
0,PAR
(z) for a vertically homogeneous water column using the information of the retrieved IOPs and the ambient optical environment.
This computation is based on an improved look-up table technology that possesses high accuracy, comparable with the full solution
of the radiative transfer equation, and meets the computational requirement of remote sensing application. This new approach
was validated by in situ measurements and an extensive model-to-model comparison with a wide range of IOPs. We successfully mapped the compensation
depth by applying this new approach to process the SeaWiFS imagery. This research suggests that E
0,PAR
(z) can be obtained routinely from ocean-color data and may have significant implications for the estimation of global heat
and carbon budget. 相似文献
107.
《Deep Sea Research Part I: Oceanographic Research Papers》2006,53(11):1742-1761
The natural isotope 234Th is used in a small-scale survey of particle transport and exchange processes at the sediment–water interface in the Benguela upwelling area. Results from water and suspended particulate matter (SPM) samples from the uppermost and lowermost water column as well as the underlying sediment of three stations are compared. The stations are situated in different sedimentological environments at 1200–1350 m water depth at the continental slope off Namibia. Highly differing extent and particle content of the bottom nepheloid layer (BNL) are determined from transmissometer data. Three models are presented, all explaining the 234Th depletion of the BNL and 234Th excess of the surface sediment that were observed. While the first model is based solely on local resuspension of surface sediment particles, the second evaluates the influence of vertical particle settling from the surface waters on the 234Th budget in the BNL. The third model explains 234Th depletion in the BNL by sedimentation of particles that were suspended in the BNL during long-range transport. Particle inventory of the BNL is highest at a depocenter of organic matter at 25.5°S, where strong deposition is presently taking place and lateral particle transport is suggested to predominate sediment accumulation. This is supported by the high settling flux of particles out of the BNL into the sediments of the depocenter, exceeding the vertical particle flux into sediment traps at intermediate depth in the same area by up to an order of magnitude. High particle residence/removal times in the BNL above the depocenter in the range of 5–9 weeks support this interpretation. Comparison with carbon mineralization rates that are known from the area reveals that, notwithstanding the large fraction of advected particles, organic carbon flux into the surface sediment is remineralized to a large extent. The deployment of a bottom water sampler served as an in situ resuspension experiment and provided the first data of 234Th activity on in situ resuspended particles. We found a mean specific activity of 86 disintegrations per minute (dpm) g−1 (39–339 dpm g−1), intermediate between the high values for suspended particles (in situ pump: 580–760 dpm g−1; CTD rosette: 870–1560 dpm g−1) and the low values measured at the sediment surface (26–37 dpm g−1). This represents essential information for the modeling of 234Th exchange processes at the sediment–water interface. 相似文献
108.
Sediment-starved sand ridges on a mixed carbonate/siliciclastic inner shelf off west-central Florida
S. E. Harrison S. D. Locker A. C. Hine J. H. Edwards D. F. Naar D. C. Twichell D. J. Mallinson 《Marine Geology》2003,200(1-4):171-194
High-resolution side-scan mosaics, sediment analyses, and physical process data have revealed that the mixed carbonate/siliciclastic, inner shelf of west-central Florida supports a highly complex field of active sand ridges mantled by a hierarchy of bedforms. The sand ridges, mostly oriented obliquely to the shoreline trend, extend from 2 km to over 25 km offshore. They show many similarities to their well-known counterparts situated along the US Atlantic margin in that both increase in relief with increasing water depth, both are oriented obliquely to the coast, and both respond to modern shelf dynamics. There are significant differences in that the sand ridges on the west-central Florida shelf are smaller in all dimensions, have a relatively high carbonate content, and are separated by exposed rock surfaces. They are also shoreface-detached and are sediment-starved, thus stunting their development. Morphological details are highly distinctive and apparent in side-scan imagery due to the high acoustic contrast. The seafloor is active and not a relict system as indicated by: (1) relatively young AMS 14C dates (<1600 yr BP) from forams in the shallow subsurface (1.6 meters below seafloor), (2) apparent shifts in sharply distinctive grayscale boundaries seen in time-series side-scan mosaics, (3) maintenance of these sharp acoustic boundaries and development of small bedforms in an area of constant and extensive bioturbation, (4) sediment textural asymmetry indicative of selective transport across bedform topography, (5) morphological asymmetry of sand ridges and 2D dunes, and (6) current-meter data indicating that the critical threshold velocity for sediment transport is frequently exceeded. Although larger sand ridges are found along other portions of the west-central Florida inner shelf, these smaller sand ridges are best developed seaward of a major coastal headland, suggesting some genetic relationship. The headland may focus and accelerate the N–S reversing currents. An elevated rock terrace extending from the headland supports these ridges in a shallower water environment than the surrounding shelf, allowing them to be more easily influenced by currents and surface gravity waves. Tidal currents, storm-generated flows, and seasonally developed flows are shore-parallel and oriented obliquely to the NW–SE trending ridges, indicating that they have developed as described by the Huthnance model. Although inner shelf sand ridges have been extensively examined elsewhere, this study is the first to describe them in a low-energy, sediment-starved, dominantly mixed siliciclastic/carbonate sedimentary environment situated on a former limestone platform. 相似文献
109.
110.
Bori L. Olla Allen J. Bejda Anne L. Studholme Walter H. Pearson 《Marine environmental research》1984,13(2):121-139
The burrowing and emergence behavior of sand worms, Nereis (Neanthes) virens Sars, in sediment contaminated with sublethal concentrations of Prudhoe Bay crude oil ranging from 74 to 5222 ppm, was studied in the laboratory. Initial burrowing in oiled sediment did not differ from that observed in unoiled sediment. Emergence of exposed worms was related to the oil concentration and the extent of weathering of oiled sediment. Sand worms buried in unoiled sediment did not emerge. Worms dug from oiled sediment after 12 hours' exposure and placed on unoiled sediment were impaired, resulting in a significant increase in time to burrow. However, after 12h, they recovered and burrowed at normal rates. Worms held in oiled sediment for 96 h also recovered. Possible causes for recovery are discussed. Results suggest that oil-induced aberrations may increase vulnerability to predation. 相似文献