中国沿海尖刺拟菱形藻的种下分类学研究*     

董焕嫦  黄春秀  徐国双  李扬 《热带海洋学报》2018,37(1):12-19

为了澄清中国沿海尖刺拟菱形藻Pseudo-nitzschia pungens Hasle的种下分类学现状, 从我国沿海分离并建立了32个尖刺拟菱形藻的单克隆培养株系, 结合光学显微镜下的群体特征和透射电镜下的超微形态学特征, 以及基于核糖体转录间隔区(ITS)的分子系统学数据, 鉴定得到尖刺拟菱形藻的两个变种: 尖刺拟菱形藻原变种P. pungens var. pungens和尖刺拟菱形藻阿维罗变种P. pungens var. averiensis。文章对其形态学特征进行了详细描述, 并利用高效液相色谱-质谱联用法(LC-MS/MS)对培养株系的多莫酸(DA)进行了检测, 但未检测到DA。  相似文献   

基于加权光滑样条的多云雨地区NDVI重构——以广东省为例     

阮柱  匡耀求 《热带地理》2020,40(6):1051-1062

为探讨加权光滑样条算法（sspw）在多云雨地区重构高质量NDVI的效果，以广东省为研究区，对其范围内2005—2015年MOD13Q1 NDVI数据进行重构。为证实sspw在重构多云雨地区NDVI的优势，选取多云雨样区的重构影像进行对比，并将未加权滤波［普通光滑样条（ssp）、Savitzky-Golay（SG）滤波］与加权滤波（sspw、加权SG滤波）重构的NDVI时序曲线进行对比。结果发现：1）sspw能有效重构多云雨地区NDVI。2）与未加权滤波相比，在质量权重的辅助下，加权滤波重构的NDVI数据时间序列曲线更接近原始NDVI上包络线，加权滤波重构的NDVI与原始NDVI线性相关性更强，误差更小；而加权滤波中，sspw比加权SG（Savitzky-Golay）滤波更能抑制图像中的噪音。总体来说，sspw重构的数据误差更小，与原始高质量数据相关性更强，重构效果更好，更适合多云雨地区。  相似文献   

Inter‐comparison of hydro‐climatic regimes across northern catchments: synchronicity,resistance and resilience     

Sean K. Carey  Doerthe Tetzlaff  Jan Seibert  Chris Soulsby  Jim Buttle  Hjalmar Laudon  Jeff McDonnell  Kevin McGuire  Daniel Caissie  Jamie Shanley  Mike Kennedy  Kevin Devito  John W. Pomeroy 《水文研究》2010,24(24):3591-3602

The higher mid‐latitudes of the Northern Hemisphere are particularly sensitive to climate change as small differences in temperature determine frozen ground status, precipitation phase, and the magnitude and timing of snow accumulation and melt. An international inter‐catchment comparison program, North‐Watch, seeks to improve our understanding of the sensitivity of northern catchments to climate change by examining their hydrological and biogeochemical responses. The catchments are located in Sweden (Krycklan), Scotland (Mharcaidh, Girnock and Strontian), the United States (Sleepers River, Hubbard Brook and HJ Andrews) and Canada (Catamaran, Dorset and Wolf Creek). This briefing presents the initial stage of the North‐Watch program, which focuses on how these catchments collect, store and release water and identify ‘types’ of hydro‐climatic catchment response. At most sites, a 10‐year data of daily precipitation, discharge and temperature were compiled and evaporation and storage were calculated. Inter‐annual and seasonal patterns of hydrological processes were assessed via normalized fluxes and standard flow metrics. At the annual‐scale, relations between temperature, precipitation and discharge were compared, highlighting the role of seasonality, wetness and snow/frozen ground. The seasonal pattern and synchronicity of fluxes at the monthly scale provided insight into system memory and the role of storage. We identified types of catchments that rapidly translate precipitation into runoff and others that more readily store water for delayed release. Synchronicity and variance of rainfall–runoff patterns were characterized by the coefficient of variation (cv) of monthly fluxes and correlation coefficients. Principal component analysis (PCA) revealed clustering among like catchments in terms of functioning, largely controlled by two components that (i) reflect temperature and precipitation gradients and the correlation of monthly precipitation and discharge and (ii) the seasonality of precipitation and storage. By advancing the ecological concepts of resistance and resilience for catchment functioning, results provided a conceptual framework for understanding susceptibility to hydrological change across northern catchments. Copyright © 2010 John Wiley & Sons, Ltd.  相似文献   

Soil moisture response to snowmelt timing in mixed‐conifer subalpine forests          下载免费PDF全文

Adrian A. Harpold  Noah P. Molotch  Keith N. Musselman  Roger C. Bales  Peter B. Kirchner  Marcy Litvak  Paul D. Brooks 《水文研究》2015,29(12):2782-2798

Western US forest ecosystems and downstream water supplies are reliant on seasonal snowmelt. Complex feedbacks govern forest–snow interactions in which forests influence the distribution of snow and the timing of snowmelt but are also sensitive to snow water availability. Notwithstanding, few studies have investigated the influence of forest structure on snow distribution, snowmelt and soil moisture response. Using a multi‐year record from co‐located observations of snow depth and soil moisture, we evaluated the influence of forest‐canopy position on snow accumulation and snow depth depletion, and associated controls on the timing of soil moisture response at Boulder Creek, Colorado, Jemez River Basin, New Mexico, and the Wolverton Basin, California. Forest‐canopy controls on snow accumulation led to 12–42 cm greater peak snow depths in open versus under‐canopy positions. Differences in accumulation and melt across sites resulted in earlier snow disappearance in open positions at Jemez and earlier snow disappearance in under‐canopy positions at Boulder and Wolverton sites. Irrespective of net snow accumulation, we found that peak annual soil moisture was nearly synchronous with the date of snow disappearance at all sites with an average deviation of 12, 3 and 22 days at Jemez, Boulder and Wolverton sites, respectively. Interestingly, sites in the Sierra Nevada showed peak soil moisture prior to snow disappearance at both our intensive study site and the nearby snow telemetry stations. Our results imply that the duration of soil water stress may increase as regional warming or forest disturbance lead to earlier snow disappearance and soil moisture recession in subalpine forests. Copyright © 2014 John Wiley & Sons, Ltd.  相似文献   

Short-term morphological changes after sand-digging during a sand sculpture activity     

庄丽华  阎军  常凤鸣  徐涛  栾振东 《中国海洋湖沼学报》2009,27(4):966-974

The morphology of the beach backshore and foreshore at Huiquan Bay, Qingdao, China, is characterized by a single intertidal sandbar system with a spring tide range of 4.59 m. The beach was measured with a laser total station of Leica TPS402. Contours of the beach were generated using data collected in March and November 2005. The survey method provided 2 mm measuring accuracy and 4–10 m horizontal spacing. The net accretion volume of the foreshore was about 11, 215 m³ from March to November. After sand sculpture activity, the axis of the sand trough migrated onshore from about 3.5 m to 17.5 m on the foreshore beach in November. At the same time, the axis of the sandbar crest migrated onshore no more than 42.25 m on the northwest foreshore; and it migrated offshore no more than 23.75 m on the southeast foreshore. On the northwest and southeast foreshore beach, two strips of erosion areas with a thickness of 0–0.2 m appeared on the sandbar crest. Accretion occurred at the bottom of the sand trough with a thickness of ∼0.2–0.6 m. The sandbar height decreased after sand sculpture activity, and it was no more than 0.7 m in March and 0.6 m in November. Human activities, such as sand digging on the sandbar crest during sand sculpture activity, also can disturb the beach morphology of intertidal bar systems. This phenomenon also was validated by comparison of beach morphology, the results of a color artificial tracer experiment and a sediment transportation trend prediction.  相似文献   

Nassarius corniculus (Olivi, 1792) (Caenogastropoda: Nassariidae): a model of environmental complexity of Italian brackish and marine habitats     

Maria Alessandra Iannotta  Francesco Toscano  & Francesco Paolo Patti 《Marine Ecology》2009,30(1):106-115

Strong environmental selection may give rise to complex species and/or camouflage the presence of sibling species in brackish waters. The prosobranch gastropod Nassarius corniculus (Olivi, 1792) is a common scavenger widely distributed in Mediterranean brackish and marine areas. We examined the morphological and molecular features of N. corniculus populations and related these features to the environmental complexity of brackish habitats. Morphological data revealed differences in radular features between specimens collected from two Mediterranean lagoons (Lake Faro, Messina, Sicily and Lake Fusaro, Gulf of Gaeta). Analysis of with the mitochondrial marker mt 16S rRNA revealed genetic variability within the Lake Faro population but did not show the different geographic structure between the two lagoons indicated by morphological data. We also predicted the gene flow of N. corniculus by comparing populations of two marine areas (Faro Sea and Ischia).  相似文献   

Morphology of pockmarks along the western continental margin of India: Employing multibeam bathymetry and backscatter data   总被引：1，自引：0，他引：1  

Sumanta Dandapath  Bishwajit Chakraborty  Siddaiah M. Karisiddaiah  Andrew Menezes  Govind Ranade  William Fernandes  Davidas K. Naik  K.N. Prudhvi Raju 《Marine and Petroleum Geology》2010

This study addresses the morphology of pockmarks along the western continental margin of India using multibeam bathymetry and backscatter data. Here, for the first time we have utilized the application of ArcGIS (Geographical Information System) for understanding the morphology of pockmarks from the western continental margin of India. The pockmarks observed in water depths of 145–330 m are circular, elliptical or elongated in plan-view, with an average length and width of 157 (±72) m and 83 (±19) m respectively. The average pockmark relief and perimeter are 1.9 (±0.9) m and 412 (±181) m, respectively. The pockmarks have average areas and volumes of 10 759 m² and 15 315 m³ respectively. Spatial separation that coincides with 210 m isobath divides the pockmarks into two groups with differing distributions and morphologies. These pockmarks originated from seepages of biogenic or thermogenic gas or from pore fluids from deeper sources, migrated vertically along the faults. Besides a possible structural control, the pockmark morphologies are also affected by bottom currents and/or by submarine slumping. The average acoustic backscatter strength from pockmark centre is higher (−35 dB) than the average backscatter of the total area (−40 dB), which suggests their possible linkage to the precipitation of diagenitic minerals from biodegradation of seepage material.  相似文献   

Manganese nodule morphology as indicators for oceanic processes in the Central Indian Basin     

《International Geology Review》2012,54(1):27-44

In order to understand the role of geological features in the depositional environment and the prevailing oceanic processes on the formation and characteristics of manganese nodules, a detailed morphological study of the manganese nodules was undertaken on 23,000 nodules from 194 locations (including 801 substations) in a nodule‐rich area covering about 150,000 km² in the Central Indian Basin (CIB). Nodules with rough surface texture dominate most of the area except the south‐eastern part of the basin, which is floored more by the smooth nodules. Smaller nodules (<4 cm) are common and are dominant both in density and mass in the south‐eastern part of the basin, whereas the north‐western part and the central part show dominance of larger rough nodules with higher density and mass. Smooth nodules are also found at shallower depth (<5000 m), on the seamount tops and along the slopes, whereas the rough nodules mostly occur in deeper areas. Significantly, the eastern part of the basin show smooth nodules with smaller size. Smooth nodules >4 cm diameter are rare and show low oxide layer thickness and low bio‐sediment remnants compared to rough surfaced nodules. Large variation in morphological types of nodules are found in the CIB with spheroidal, oblong, triangular, rounded, sub‐rounded or irregular shapes, with irregular nodules being most common. The most common nucleus is altered basalt, while pumice, shark teeth, clay and older nodule nuclei are also present. Water currents and seafloor topography seem to play a major role in defining the nodule morphology. Results of the study show the abundance of smaller nodules with smooth surface texture towards the eastern side of the study area. These features are probably responding to bottom current activity. Inasmuch as the eastern part of the study area is closer to saddles in the Ninety East Ridge (which is the entry point of the Antarctic Bottom Water (AABW) currents into the CIB), the influence of AABW is reflected in the shape and size of the nodules in this area.  相似文献   

宁芜和庐枞火山岩盆地玢岩铁矿矿床地球化学特征及其成矿动力学背景探讨   总被引：3，自引：0，他引：3  

陈津华  曾键年  王思源  李锦伟  邱金亮  张燕 《地质科技情报》2012,31(1):86-94

玢岩铁矿是我国铁矿的一个重要成矿类型,宁芜和庐枞火山岩盆地是长江中下游地区玢岩铁矿的主要矿集区.对宁芜和庐枞盆地的构造分析结果表明,NNE向断裂和NW向断裂控制了区内的岩浆活动,断裂的交汇部位往往是玢岩铁矿产出的有利空间.综合对比了宁芜和庐枞地区玢岩铁矿成矿岩体的主量元素、稀土元素以及铅同位素特征,表明其具有相似的地球化学特征和共同的物质来源.稀土元素特征表明两盆地玢岩铁矿的成矿物质主要来源于地幔或下地壳;Pb同位素特征则进一步说明其与EM-Ⅱ型富集地幔具有密切关系.宁芜和庐枞盆地在燕山期受太平洋板块俯冲作用的影响,成矿作用受岩浆活动所控制.两盆地玢岩铁矿成矿作用的差异,可能是由于其受地壳物质混染程度不同所致.  相似文献   

Crystal Structure and Chemical Composition of Ludwigite from Vranovac Ore Deposit (Boranja Mountain,Serbia)     

Pavle TAN?I?  Radovan DIMITRIJEVI?  Maja POZNANOVI?  Aleksandar PA?EVSKI  Slobodanka SUDAR 《《地质学报》英文版》2012,86(6):1524-1538

The crystal structure of ludwigite from Vranovac ore deposit (Boranja Mt., Serbia) was refined using the X-ray powder diffraction (XRPD) Rietveld method in the space group Pbam to a final RB=7.45% and RF=5.26%. It has the unit cell dimensions of: a=9.2515(2) ?; b=12.3109(2) ?; c=3.03712(7) ?; and V=345.91(1) ?3. The calculated distances and angles are mostly in good agreement with the Mg2+-Fe2+ substitutions across the M(1) and M(3) sites, as well as with the Fe3+-Al3+ replacement in the M(4) site. However, the mean observed M(2)-O distance is considerably shorter than prescribed, due to a slight increase of the Fe3+ content in the M(2) site. Such replacement was compensated by slight increase of the Fe2+ content in the M(4) site, resulting in the (Mg1.48Fe2+0.46Fe3+0.05Mn0.02)2.01(Fe3+0.94Fe2+0.04Al0.02)1.00B1.00O5 composition. The formation temperature was estimated to be about 500–600°C. The influences of the various chemical compositions to the crystallographic parameters, M-O distances, M(3) and M(4) sites shift, distortion parameters and estimated valences, were also studied and compared with other reference samples.  相似文献