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1.
Surface waters of the subtropical Sargasso Sea contain dissolved inorganic phosphate (DIP) concentrations of 0.2 to 1.0 nanomolar, which are sufficiently low to result in phosphorus control of primary production. The DIP concentrations in this area (which receives high inputs of iron-rich dust from arid regions of North Africa) are one to two orders of magnitude lower than surface levels in the North Pacific (where eolian iron inputs are much lower and water column denitrification is much more substantial). These data indicate a severe relative phosphorus depletion in the Atlantic. We hypothesize that nitrogen versus phosphorus limitation of primary production in the present-day ocean may be closely linked to iron supply through control of dinitrogen (N2) fixation, an iron-intensive metabolic process. Although the oceanic phosphorus inventory may set the upper limit for the total amount of organic matter produced in the ocean over geological time scales, at any instant in geological time, oceanic primary production may fall below this limit because of a persistent insufficient iron supply. By controlling N2 fixation, iron may control not only nitrogen versus phosphorus limitation but also carbon fixation and export stoichiometry and hence biological sequestration of atmospheric carbon dioxide. 相似文献
2.
Boyle EA 《Science (New York, N.Y.)》1990,249(4971):863-870
During the past decade, geochemical paleoceanographers have begun to explore the changes in the circulation of the deep ocean that occurred during the glacial-interglacial cycles of the earth's recent history. The deep ocean was significantly colder during the glacial maximum. The distributions of biologically utilized elements (such as carbon and phosphorus) were significantly different as well; higher concentrations of these elements occurred in the deep (>2500 meters depth) North Atlantic, and lower concentrations occurred in the upper (<2500 meters depth) waters of the North Atlantic and possibly in all of the major ocean basins. In contrast, relatively subtle changes have been observed in the radiocarbon ages of deep waters. Slow deepwater changes are statistically linked to variations in the earth's orbit, but rapid changes in deepwater circulation also have occurred. Deepwater chemistry and circulation changes may control the variability in atmospheric CO(2) levels that have been documented from studies of air bubbles in polar ice cores. 相似文献
3.
The Redfield ratio [carbon:nitrogen:phosphorus (C:N:P)] of particle flux to the deep ocean is a key factor in marine biogeochemical cycling. Changes in oceanic carbon sequestration have been linked to variations in the Redfield ratio on geological time scales, but this ratio generally is assumed to be constant with time in the modern ocean. However, deep-water Redfield ratios in the northern hemisphere show evidence for temporal trends over the past five decades. The North Atlantic Ocean exhibits a rising N:P ratio, which may be related to increased deposition of atmospheric nitrous oxides from anthropogenic N emissions. In the North Pacific Ocean, increasing C:N and C:P ratios are accompanied by rising remineralization rates, which suggests intensified export production. Stronger export of carbon in this region may be due to enhanced bioavailability of aeolian iron. These findings imply that the biological part of the marine carbon cycle currently is not in steady state. 相似文献
4.
宁波 《上海海洋大学学报》2012,21(3):469-474
上海是一座"因海而生,因海而兴"的滨海国际大都市。从海洋文化社会视角分析上海的城市变迁,有助于剖析上海城市变迁的内在动力,把握和理解上海城市精神的内涵,探讨上海城市变迁的发展趋势。在史料分析的基础上,从海洋文化视角分析归纳出上海曾历经江南渔村、国内贸易港口、远东航运中心、国际航运中心等海洋文化社会形态的变迁;发现上海经济社会的发展,受益于海洋文化的滋润和影响,得益于海洋精神这一根本动力。因此,从某种意义上而言,上海的城市变迁主要是海洋文化作用于上海城市发展的结果,是海洋精神内在动力外化的直接反映。城市发展的最高阶段是成为国际文化中心。由于上海富有海洋文化特色的独特城市精神,因此,上海在建成"四个中心"之后,将会逐步发展成为一座以海洋文化为主要元素的国际文化中心。 相似文献
5.
Garrett C 《Science (New York, N.Y.)》2003,301(5641):1858-1859
Recent satellite and in situ observations have shown that at ocean ridges and other seafloor topographic features, a substantial amount of energy is transferred from the main ocean tides into "internal tides." In his Perspective, Garrett explains how these internal waves with tidal periods propagate through the density-stratified deep ocean and eventually break down into turbulence. The resulting mixing affects ocean stratification and ocean circulation. It thus influences climate as well as biological production. The energy for the internal tides is derived from the rotational energy of the Earth-Moon system changes of the length of the day and the distance to the Moon. 相似文献
6.
海洋类土壤改良剂对土壤理化性状及烤烟生长和产量的影响 总被引：3，自引：0，他引：3
为研究海洋类土壤改良剂的作用效果,采用田间对比试验,分析了虾肽肥、鱼蛋白肥、海藻肥3种海洋类土壤改良剂对土壤理化性状及烤烟生长和产量的影响。结果表明:施用虾肽肥可于移栽后55 d有效提高土壤碱解氮、速效钾含量,但对烤烟生长和产量无明显影响;施用鱼蛋白肥可显著提升55 d时土壤碱解氮、有效磷、速效钾水平,显著提高烟株根系活力、中部叶最大叶长、干物质积累量,其烤后烟叶产量、产值分别较对照提高27.79%、29.84%;施用海藻肥可明显降低75 d时土壤容重,于55 d显著提升土壤碱解氮、有效磷、速效钾水平,显著提高中部叶最大叶长、干物质积累量,其烤后烟叶产量、产值分别较对照提高11.75%、20.05%。综上,施用鱼蛋白肥、海藻肥可在一定程度上改良土壤,有效促进烤烟生长,显著提高烟叶产量。 相似文献
7.
The figures in Table 1 yield some interesting results. The total annual value of food and mineral resources taken from the ocean is $8.3 billion, in contrast to $309 billion from the land. Using the land value as the yardstick, if the annual value of produce from the ocean were in ratio to the area relationship of ocean and land, the ocean potential would be $750 billion; the actual recovery for 1964 was only 1.1 percent of that potential. This very low percentage is the basis for either great optimism for the future development of the ocean (on the basis of unrealized potential), or great pessimism (on the basis of high costs compared with further development of land resources, or present exploitation to near the limit of productivity). 相似文献
8.
Using the new Argo array of profiling floats that gives unprecedented space-time coverage of the upper 2000 meters of the global ocean, we present definitive evidence of a deep tropical ocean component of the Madden-Julian Oscillation (MJO). The surface wind stress anomalies associated with the MJO force eastward-propagating oceanic equatorial Kelvin waves that extend downward to 1500 meters. The amplitude of the deep ocean anomalies is up to six times the amplitude of the observed annual cycle. This deep ocean sink of energy input from the wind is potentially important for understanding phenomena such as El Ni?o-Southern Oscillation and for interpreting deep ocean measurements made from ships. 相似文献
9.
The vertical flux of nitrate across the thermocline in the upper ocean imposes a rigorous constraint on the rate of export of organic carbon from the surface layer of the sea. This export is the primary means by which the oceans can serve as a sink for atmospheric carbon dioxide. For the oligotrophic open ocean regions, which make up more than 75% of the world's ocean, the rate of export is currently uncertain by an order of magnitude. For most of the year, the vertical flux of nitrate is that due to vertical turbulent transport of deep water rich in nitrate into the relatively impoverished surface layer. Direct measurements of rates of turbulent kinetic energy dissipation, coupled with highly resolved vertical profiles of nitrate and density in the oligotrophic eastern Atlantic showed that the rate of transport, averaged over 2 weeks, was 0.14 (0.002 to 0.89, 95% confidence interval) millimole of nitrate per square meter per day and was statistically no different from the integrated rate of nitrate uptake as measured by incorporation of (15)N-labeled nitrate. The stoichiometrically equivalent loss of carbon from the upper ocean, which is the relevant quantity for the carbon dioxide and climate question, is then fixed at 0.90 (0.01 to 5.70) millimole of carbon per square meter per day. These rates are much lower than recent estimates based on in situ changes in oxygen over annual scales; they are consistent with a biologically unproductive oligotrophic ocean. 相似文献
10.
滇池水体沉积物磷素特征及其对藻类的影响 总被引：2，自引：1，他引：1
为揭示在外源磷得到控制的情况下,滇池沉积物磷在适宜条件下释放特征及其对藻类的影响,采用室外模拟方法,研究滇池沉积物与上覆水中的磷素特征,探索沉积物磷释放对藻类的影响。结果表明：上覆水下层水中各形态磷（总磷、可溶性磷、正磷酸盐）含量高于上层水;沉积物中磷素形态以钙结合态磷和有机磷为主,向水体释放贡献最大的是铁铝结合态磷和有机磷;水中正磷酸盐与水中叶绿素a含量呈正相关关系,正磷酸盐含量升高显著加剧水体富营养化;沉积物中可交换态磷含量与水体叶绿素a呈极显著正相关,沉积物磷释放是藻类生长的最主要内源负荷。研究表明,控制水体中的正磷酸盐和沉积物中铁铝结合态磷的浓度以及限制有机磷的转化和矿化是控制藻类的有效措施。 相似文献
11.
南方红壤处理滇池水的初步试验 总被引：8，自引：0，他引：8
以含磷极低、富含铁铝氧化物、对磷具有较强的吸附和固定能力的南方红壤为材料，用该土壤对滇池水进行了去磷效果的初步试验。结果表明，该土壤对水体磷的去除效果较好，但去除效果与土壤加入量、处理中的振荡时间、振荡强度及水体的理化性质相关。模拟结果表明，有效处理土壤或选用理想的材料，可以更好地去除水体磷。 相似文献
12.
Mayewski PA Meeker LD Whitlow S Twickler MS Morrison MC Bloomfield P Bond GC Alley RB Gow AJ Meese DA Grootes PM Ram M Taylor KC Wumkes W 《Science (New York, N.Y.)》1994,263(5154):1747-1751
High-resolution, continuous multivariate chemical records from a central Greenland ice core provide a sensitive measure of climate change and chemical composition of the atmosphere over the last 41,000 years. These chemical series reveal a record of change in the relative size and intensity of the circulation system that transported air masses to Greenland [defined here as the polar circulation index (PCI)] and in the extent of ocean ice cover. Massive iceberg discharge events previously defined from the marine record are correlated with notable expansions of ocean ice cover and increases in PCI. During stadials without discharge events, ocean ice cover appears to reach some common maximum level. The massive aerosol loadings and dramatic variations in ocean ice cover documented in ice cores should be included in climate modeling. 相似文献
13.
An unresolved issue in ocean and climate sciences is whether changes to the surface ocean input of the micronutrient iron can alter the flux of carbon to the deep ocean. During the Southern Ocean Iron Experiment, we measured an increase in the flux of particulate carbon from the surface mixed layer, as well as changes in particle cycling below the iron-fertilized patch. The flux of carbon was similar in magnitude to that of natural blooms in the Southern Ocean and thus small relative to global carbon budgets and proposed geoengineering plans to sequester atmospheric carbon dioxide in the deep sea. 相似文献
14.
《农业环境科学学报》2013,32(7)
通过将磷吸收饱和的镧/铝改性沸石分别放入pH为2.0、3.0、4.0、5.0、6.0、7.0、8.0、9.0、10.0、11.0、12.0、13.0的溶液中,研究了镧/铝改性沸石的最佳磷释放条件,并在最佳磷吸附和最佳磷释放条件下研究了镧/铝改性沸石的再生能力。结果表明,当pH变化在2~13时,镧/铝改性沸石的磷释放量和释放百分比随pH的升高先降低后升高,其中：pH为2和12~13时的磷释放率较高,在76%以上,且pH13时的释放率最大,为98.2%;而pH在3~11时,磷释放率较低,在30%以下,且pH6时的释放率最小,为1.7%。表明强酸或强碱环境有利于镧/铝改性沸石中磷的释放。对镧/铝改性沸石再生能力的研究显示,经过4次再生后,镧/铝改性沸石的磷吸附量和再生能力分别为2.367、2.336、2.312、2.253 mg·g-1和96.7%、95.5%、94.5%、92.1%,虽然吸附剂的磷吸附能力随再生次数的增加呈现逐渐降低的趋势,但经过4次再生后,其对磷的吸附能力仍保持在92%以上,表明镧/铝改性沸石具有较好的稳定性和再生能力。 相似文献
15.
磷是植物生长必需的营养元素之一,在农业生产中起着关键作用。然而,长期过量的磷肥投入导致土壤磷素水平增加,进而加大了土壤磷素流失风险,造成农业非点源磷污染,同时这也成为导致水体富营养化的主要因素之一。因此,识别和管理农业非点源磷的流失风险关键区,成为面源污染亟待解决的关键问题。磷指数模型起源于20世纪90年代,是评估农田磷流失潜力和指导磷管理决策的重要工具之一。根据研究区特点,美国众多学者在各州设立了不同的磷指数指标体系,优化了磷指数的组成因子、计算方法和分级标准。本文对美国各州磷指数模型评价体系进行了综述和评价,指出了磷指数模型的局限性,提出了改进方向,以期为我国磷素管理方法提供借鉴。 相似文献
16.
国内外海洋能发电测试场研究现状 总被引：1，自引：1，他引：0
海洋能作为一种重要的海洋资源和清洁能源,其开发和利用是国家发展战略的必然要求。海洋能发电测试场能对海洋能装置进行实海况并网试验,是海洋能装置从工程样机走向规模产业化应用的关键环节。介绍了目前国外大型的波浪能、潮流能测试场的建设与运行情况,并做了简要的对比分析;还介绍了当前我国在海洋能试验与测试场建设方面的进展、现状及相关技术。探讨了我国海洋能发电进行并网测试的必要性,指出建设海洋能发电测试场是保证我国海洋能资源的有效利用途径。 相似文献
17.
海洋渔业可持续发展研究进展 总被引：1，自引：0，他引：1
随着陆地资源的日益衰竭,人们将目光转移到了海洋这片蓝色国土上,可是人们盲目的捕捞和开采,给海洋带来了巨大的伤害,越来越多的学者开始探究如何保护海洋,使海洋不会重蹈陆地的覆辙,能够实现可持续发展。而在海洋的诸多资源中,又以渔业为最重要的资源,国内外众多学者为了实现海洋渔业的可持续发展进行了大量的研究和探索。 相似文献
18.
Hotspots, basalts, and the evolution of the mantle 总被引：2，自引：0，他引：2
Anderson DL 《Science (New York, N.Y.)》1981,213(4503):82-89
The trace element concentration patterns of continental and ocean island basalts and of mid-ocean ridge basalts are complementary. The relative sizes of the source regions for these fundamentally different basalt types can be estimated from the trace element enrichment-depletion patterns. Their combined volume occupies most of the mantle above the 670 kilometer discontinuity. The source regions separated as a result of early mantle differentiation and crystal fractionation from the resulting melt. The mid-ocean ridge basalts source evolved from an eclogite cumulate that lost its late-stage enriched fluids at various times to the shallower mantle and continental crust. The mid-ocean ridge basalts source is rich in garnet and clinopyroxene, whereas the continental and ocean island basalt source is a garnet peridotite that has experienced secondary enrichment. These relationships are consistent with the evolution of a terrestrial magma ocean. 相似文献
19.
The ocean is an electrically conducting fluid that generates secondary magnetic fields as it flows through Earth's main magnetic field. Extracting ocean flow signals from remote observations has become possible with the current generation of satellites measuring Earth's magnetic field. Here, we consider the magnetic fields generated by the ocean lunar semidiurnal (M2) tide and demonstrate that magnetic fields of oceanic origin can be clearly identified in satellite observations. 相似文献
20.
海洋石油污染物微生物降解的研究 总被引：1，自引：0，他引：1
[目的]探讨微生物降解海洋石油污染物的最佳条件。[方法]选择大庆原油为降解底物,以分离的优势石油降解菌为研究对象,首先通过单因素试验研究了初始盐度、pH和营养盐等因素对菌株SY1和SY2降解石油的影响,然后通过正交试验确定最佳降解条件。[结果]单因素试验表明,初始pH和氮源浓度对菌株降解石油的影响较显著,同时添加氮、磷营养盐能取得更好的降解效果。正交试验表明,菌株SY1在最优组合下石油降解率达59.0%,主要影响因素是磷浓度;菌株SY2在最优组合下石油降解率为57.4%,主要影响因素是盐度和pH。[结论]该研究为菌株对石油降解性能的研究提供了理论参考。 相似文献