长江口海水盐度和悬浮体对中肋骨条藻生长的影响   总被引：3，自引：0，他引：3  

李金涛  赵卫红  杨登峰  王江涛 《海洋科学》2005,29(1):34-37

2001年5月通过实验室培养的方法研究了长江口优势赤潮浮游植物种类——中肋骨条藻(Skeletonema costatum)在长江口海水中的生长情况。实验结果显示,在实验光强范围内该藻相对生长速率常数随光强的减小而减小,表明光照的可得性是影响其生长的重要因素;悬浮体的遮光效应会限制其生长。海水盐度超出其适宜生长的范围也会对其的生长产生不利影响。两个相互对比的实验说明在泥沙含量很高的长江口咸淡混合水中光照的可得性和盐度均影响中肋骨条藻的生长,综合这两个因素,在实验盐度范围内最适宜中肋骨条藻生长的盐度是约为19．2的咸淡水。适于中肋骨条藻适宜生长的盐度为14～23。  相似文献   

Sequential Separation of Uranium,Hafnium and Neodymium from Natural Waters Concentrated by Iron Coprecipitation          下载免费PDF全文

Carli A. Arendt  Sarah M. Aciego  Kenneth W.W. Sims  Mark Robbins 《Geostandards and Geoanalytical Research》2015,39(3):293-303

A new ion exchange chromatography method is presented for the isolation of high field‐strength elements (HFSE) from freshwater and seawater samples that have undergone iron coprecipitation. Large volumes of water can be condensed through the application of iron coprecipitation, but clean separation of elements from the precipitate proves difficult. The technique described is a five‐column process designed to separate the HFSE, including rare earth elements such as neodymium and hafnium, before removing the iron and isolating uranium. Subsequent isolation of Nd and Hf was achieved using established ion exchange chromatography methods. The efficacy of our chemistry was verified by measurements of analytical reference materials – both reference solutions and seawater samples – subjected to the chemical separation methods described. Elution results indicate high yields (> 90%) determined by concentration measurements of a known reference material added to each column. Measurement results for isotopic compositions of seawater (U, Nd) and reference solutions (NIST SRM 960, U) were identical within uncertainty to previously published values. Compositions were identical between solutions (Spex CLMS3, Spex PLND2) that underwent different iron coprecipitation procedures. Isotopic determinations for reference materials JNdi‐1 and NIST SRM 960 measured with the mass spectrometers used in this study were in agreement with universally accepted values for these materials, and indicate high precision.  相似文献   

Changes to the Canadian Arctic Archipelago Sea Ice and Freshwater Fluxes in the Twenty-First Century under the Intergovernmental Panel on Climate Change A1B Climate Scenario     

Xianmin Hu  Paul G. Myers 《大气与海洋》2014,52(4):331-350

A coupled ocean and sea-ice pan-Arctic model forced by the Intergovernmental Panel on Climate Change A1B climate scenario is used to study the evolution of ice and ocean surface conditions within the Canadian Arctic Archipelago (CAA) during the twenty-first century. A summer ice-free CAA is likely by the end of our simulation. Sea ice undergoes significant changes from the mid-2020s to the mid-2060s in both concentration and thickness. The simulation shows a shrinking of 65% and a thinning of 75% in summer over the 40 years, resulting in a partially open Northwest Passage by the 2050s. However, ice in central Parry Channel might increase due to a decrease in export from April to June, linked to a reduced cross-channel sea surface height (SSH) gradient, before melting thermodynamically. On a larger scale, the central CAA throughflow will experience a significant decrease in both volume and freshwater transport after 2020, which is related to the change in the SSH difference between the two ends of Parry Channel, particularly the lifting of SSH in Baffin Bay. With a lower albedo, a warmer ocean is simulated, particularly in summer. The sea surface salinity within the CAA demonstrates a strong decadal oscillation without a clear trend over the entire simulation. A north–south pattern, separated by Parry Channel, is also found in the changes of ocean temperature and salinity fields due to different ice conditions.  相似文献   

Variation of freshwater components in the Canada Basin during 1967–2010   总被引：2，自引：0，他引：2  

PAN Hong  CHEN Min  TONG Jinlu  QIU Yusheng  ZHENG Minfang  CAO Jianping 《海洋学报(英文版)》2014,33(6):40-45

As a conservative tracer, oxygen isotopes in seawater are widely used for water mass analysis, along with temperature and salinity. In this study, seawater oxygen-18 datasets in the Canada Basin during 1967–2010 were obtained from the four cruises of the Chinese National Arctic Research Expedition(1999, 2003, 2008, and 2010) and the NASA database. Fractions of sea ice meltwater and river runoff were determined from the salinity-18O system. Our results showed that the river runoff decreased from the south to the north in the Canada Basin. The enhanced amount of river runoff observed in the southern Canada Basin may originate from the Mackenzie River, transported by the Beaufort Gyre. The river runoff component showed maximum fractions during 1967–1969, 1978–1979, 1984–1985, 1993–1994, and 2008–2010, indicating the refresh time of the river runoff was 5.0–16.0 a in the Canada Basin. The temporal variation of the river runoff was related to the change of the Arctic Oscillation(AO) index, suggesting the freshwater stored in the Canada Basin was affected by surface sea ice drift and water mass movement driven by atmospheric circulation.  相似文献   

A Comparative study on the nonspecific immunity of juvenile Litopenaeus vannamei ever inhabiting freshwater and seawater     

Xuying Jia  Sen Ding  Fang Wang  Shuanglin Dong 《中国海洋大学学报(英文版)》2014,13(3):472-478

A study on the nonspecific immunity of Litopenaeus vannamei ever inhabiting freshwater and seawater was carried out at different molt stages by comparing their total hemocyte count(THC) and respiratory burst(RB) and activity of phenol oxidase(PO), nitric oxide synthase(NOS) and lysozyme(LY). Two-way ANOVA showed that salinity and molt stage independently affected THC and RB and the activity of PO, NOS and LY of juvenile L. vannamei significantly(P 0.05). The THC and RB and the activity of NOS gradually increased from the post-molt stages(A and B) to the pre-molt stages(D0–D3), which were common in shrimps inhabiting freshwater and seawater. The activity of PO peaked at the inter-molt stage(C), and touched the lowest at the post-molt stage in freshwater and pre-molt stage in seawater. The activity of LY was stable over the molt cycle. The RB and the activity of PO, NOS and LY of juvenile L. vannamei were significantly lower in freshwater than in seawater; whereas THC was significantly higher in freshwater than in seawater(P 0.05). It was concluded that the post-molt stage(especially stage A) was critical to shrimp culture, which should be intensively attended when L. vannamei was cultured in freshwater.  相似文献   

Simulated Spatiotemporal Response of Ocean Heat Transport to Freshwater Enhancement in North Atlantic and Associated Mechanisms          下载免费PDF全文

YU Lei  GAO Yongqi 《Acta Meteorologica Sinica》2011,25(3):364-375

The Atlantic Meridional Overturning Circulation(AMOC)transports a large amount of heat to northern high latitudes,playing an important role in the global climate change.Investigation of the freshwater perturbation in North Atlantic(NA)has become one of the hot topics in the recent years.In this study,the mechanism and pathway of meridional ocean heat transport(OHT)under the enhanced freshwater input to the northern high latitudes in the Atlantic are investigated by an ocean-sea ice-atmosphere coupled model.The results show that the anomalous OHT in the freshwater experiment(FW)is dominated by the meridional circulation kinetic and ocean thermal processes.In the FW,OHT drops down during the period of weakened AMOC while the upper tropical ocean turns warmer due to the retained NA warm currents.Conversely,OHT recovers as the AMOC recovers,and the mechanism can be generalized as:1)increased ocean heat content in the tropical Southern Ocean during the early integration provides the thermal condition for the recovery of OHT in NA;2)the OHT from the Southern Ocean enters the NA through the equator alongthe deep Ekman layer;3)in NA,the recovery of OHT appears mainly along the isopycnic layers of 24.70-25.77 below the mixing layer.It is then transported into the mixing layer from the "outcropping points"innorthern high latitudes,and finally released to the atmosphere by the ocean-atmosphere heat exchange.  相似文献   

河北省唐海县地下淡水资源均衡分析     

贾秋刚  杨婧 《城市地质》2011,6(1):26-29

随着唐海县的工业和人口发展迅速,地下水处于超采状态。本文采用水均衡法,分析了唐海县地下淡水的补给与排泄量,区内年平均总负均衡为979.76×10~4m~3/a。为唐海县水资源的可持续利用提供了依据。  相似文献   

CO₂浓度升高对三江平原湿地活性有机碳及土壤微生物的影响   总被引：2，自引：0，他引：2  

赵光影  刘景双  王洋  周嘉 《地理与地理信息科学》2011,27(2):96-100

利用开顶箱薰气室,设置正常大气CO2浓度(Ambient CO2,350 umol·mol-1)和高CO2浓度(Elevated CO2,700μmol·mol-1)2个水平和不施氮(NN,0 gN·m-2)、常氮(MN,5 gN·m-2)、高氮(HN,15 gN·m-2)3个氮素水平,研究CO2浓度升高和氮肥施用对三江平原草甸小叶章湿地(Calamagrostis angustifolia)土壤活性有机碳及微生物的影响。结果表明,CO2浓度升高条件下,土壤微生物量碳(MBC)和溶解性有机碳(DOC)呈增加趋势,易氧化有机碳(LOC)和水溶性碳水化合物碳(CHC)的变化因生长期和氮素水平而异。CO2浓度升高,小叶章湿地土壤微生物数量在不同的生长时期呈现不同的响应趋势。细菌数量在腊熟期增幅最大,为31.4%;真菌数量在腊熟期增加16.6%,成熟期增加24.3%;放线菌数量没有发生明显变化。相关分析表明,细菌、真菌和放线菌数量都与土壤微生物量碳呈显著相关。湿地土壤中的活性有机碳可以为土壤微生物提供更多的有效能量,从而加快湿地生态系统养分循环过程。  相似文献   

Source of a freshwater influx at the last glacial maximum in the Indian Ocean: An alternative interpretation     

S. K. Gupta  P. Sharma  S. K. Shah 《第四纪科学杂志》1992,7(3):247-255

Recent analysis of a sediment core in the eastern Arabian Sea revealed a negative pulse of about 1% in the δ¹⁸O value of the planktonic Foraminifera around the last glacial maximum (LGM). This pulse has been attributed to (i) increased runoff into the Bay of Bengal from the east-flowing south Indian rivers due to enhancement of the northeast winter monsoon, and (ii) an increase in Arabian sea-surface temperature caused by the weakening of the southwest monsoon at the LGM. We show that the speculation on which the latter hypothesis is based, is not supported by observational data and cannot fully account for the observed magnitude of the spike. With a view to assessing the validity of the first mechanism, we have modelled the mixed layer of the Bay of Bengal as a well-mixed box. The model calculations show that to account for the pulse requires a change of about 10% in either the annual rate of river input or its isotopic composition. For the northeast monsoon to account for the pulse it would mean that the rainfall should have increased by a factor of five to ten during the LGM. No evidence for such an increase is indicated in the available palaeoclimatic data. We explain the freshwater spike by invoking increased discharge of glacial meltwater from the Tibetan plateau into the Bay of Bengal. We show that the proxy climate data from the Indo-Tibetan region that has become available recently provides substantial evidence for the occurrence of a warming event around the LGM, which supports our mechanism.  相似文献   

Heterogeneous timing of freshwater input into Kobbefjord,a low-arctic fjord in Greenland     

Jakob Abermann  Kirsty Langley  Sille M. Myreng  Kerstin Rasmussen  Dorthe Petersen 《水文研究》2021,35(11):e14413

The majority of freshwater input from Greenland to the global ocean stems from the Greenland Ice Sheet. Currently, almost a quarter of the freshwater flowing from Greenland is derived from catchments that are disconnected from the Greenland Ice Sheet. Despite their importance to the total freshwater flux and influence on fjord geochemistry, there is relatively little monitoring data available for those catchments and therefore the drivers of regional differences in export are largely unknown. We present a dataset of 12 years of discharge of four catchments less than 15 km apart, that are different in size (between 7 and 32 km²), local glacier coverage (4%–11%) and lake cover (0%–5%). They all drain into Kobbefjord, a well-studied fjord in West Greenland, near Greenland's capital Nuuk. Between catchments, the magnitude of discharge varies at annual, seasonal and sub-daily timescales, due to differences in physical catchment properties as well as local climate variability. We find that annual specific discharges vary greatly (between 1.2 and 1.9 m/year on a 12-year average) due to a longitudinal precipitation gradient from West to East caused by different amount of orographic precipitation shading. The seasonal cycle of discharge (amplitude, timing and minimum flow) differs among the sites mainly due to different exposure to solar radiation as a driver for major snowmelt; the small ice coverage in the catchments plays only a minor role in discharge variability. Dry years generally increase the relative differences in annual specific discharge and no significant temporal trends have been found in the studied catchments. On a sub-daily timescale, the difference in timing of maximum discharge during fair-weather days (>80% maximum solar radiation and no precipitation) ranged between 7 and 12 h, which is attributed to differences between the presence and elevation of lakes among the catchments. The response of discharge to major precipitation events is discussed, where a delay of between 5 and 7 h is found for the catchments that do not contain lakes near the gauge.  相似文献