排序方式： 共有47条查询结果，搜索用时 421 毫秒
1.
From 2007 to 2011, large-scale green tides formed by unattached filamentous alga, Ulva prolifera in Ulva linza–procera–prolifera complex, have initially occurred in Jiangsu coasts of China. The real niche or the substrate(s) on which U. prolifera attaches before it starts to float is still under debate. However, great numbers of Ulva propagules would be supposed to exist in the microscopic, overwintering stage for the next spring's bloom in coastal environments. This study was designed to confirm the above prediction and investigate abundance, species composition and growth characteristics of Ulva propagules in the sediments. Quantification result showed that Ulva propagules widely distributed in the sediments and the abundance of these isolates did not change much over a 3-month testing period at low temperature in darkness. Molecular data based on three DNA markers revealed that four Ulva species existed in the sediments, among which green-tide forming alga, U. prolifera, was included. Elevated levels of temperature, irradiance as well as nutrients in seawater greatly facilitated recovery and growth of propagules. Results of this investigation indicated the possibility of microscopic propagules turning directly into floating biomass in season when temperature, irradiance and nutrients together meet the required levels in questioned coastal water area. 相似文献
2.
本研究利用吸收光谱和荧光激发-发射矩阵光谱-平行因子分析(EEMs-PARAFAC),研究了养马岛附近海域海水中有色溶解有机质(CDOM)的浓度、组成、来源和生物可利用性,并估算了浮游植物生长繁殖对CDOM及具有生物可利用性CDOM的贡献。结果表明,表、底层海水中CDOM浓度(以吸收系数a350计)平均值分别为1.62±0.42 m-1和1.30±0.47 m-1,光谱斜率(S275-295)平均值分别为0.022±0.003 nm-1和0.023±0.003 nm-1。利用PARAFAC模型识别出4种荧光组分,分别为陆源类腐殖酸C1、类色氨酸C2、类酪氨酸C3和微生物源类腐殖酸C4。荧光指数(FIX)、腐殖化指数(HIX)和生物指数(BIX)显示,CDOM受陆源输入和海洋自生源的综合影响。降解实验结果显示,表、底层海水中生物可利用性CDOM百分比(%△a350)平均值分别为(23.36%±17.94%)和(8.93%±20.30%)。C1、C2和C4组分的荧光强度在培养之后降低,而C3组分的荧光强度上升。各荧光组分生物可利用性依次递减的顺序为:%△C1(23.75%±8.96%)＞%△C4(20.83%±11.71%)＞%△C2(11.67%±38.87%)＞%△C3(-29.61%±39.90%),显示培养之后CDOM的平均分子量和腐殖化程度降低。表层海水中a350、%△a350与Chl a之间存在显著线性相关关系,据此可以估算出浮游植物生长繁殖对CDOM的贡献为36.9%,对具有生物可利用性CDOM的贡献为85.0%。 相似文献
3.
作者根据2012年5月和2013年11月对日照近岸海域进行的底拖网调查资料,分析了该海域虾蟹类的种类组成、优势种和生物多样性。调查海域共捕获虾蟹类25种,根据相对重要性指数计算优势种为8种,其中经济价值较高的中大型虾蟹类5种,分别为:口虾蛄(Oratosquilla oratoria)、戴氏赤虾(Meraenaeopsis dalei)、鹰爪虾(Trachypenaeus curvirostris)、日本[虫寻](Charybdis japonica)和三疣梭子蟹(Portunus trituberculatus)。分别计算了日照近岸海域春、秋季虾蟹类群落的多样性指数(H')、丰富度指数(D)和均匀度指数(J)。该海域虾蟹类群落多样性整体处在较低的水平,在生物量和丰度上经济较高的中大型虾蟹类物种占据优势。 相似文献
4.
本文利用尽可能多的观测资料和WRF-3.4.1模式(Weather Research and Forecasting Model)对2012年1月19日至28日发生在西南印度洋上空的1次强热带气旋进行了研究,并分析其时空结构和发展机制。对该热带气旋的移动路径、强度及内部结构的数值模拟结果与实际符合较好。分析表明,感热和凝结潜热贯串于热带气旋发展的整个过程,其中感热对气旋发展的影响较弱,凝结潜热是气旋发展的主要能量来源,CISK机制可解释该热带气旋的发展过程。 相似文献
5.
2016年5月和8月浒苔暴发前后,分别对日照近岸海域浒苔暴发区进行了两个航次的浮游植物断面调查。两个航次中,硅藻都占据了调查海域浮游植物组成的主导地位,在种类数上和细胞丰度值上都占了较大的比例。8月航次细胞丰度明显高于5月航次,这与调查海域的历次调查结果相一致。应用PRIMER软件中的单变量分析得到群落种数(S)、丰富度(d)、香农-威纳指数(Shannon-Weaner index)(H′)和均匀度(J),从多样性指数分析可以看出,5月航次的生物多样性优于8月航次,5月航次调查海域浮游植物种类数量和空间分布都较均匀。两个航次中出现的优势种存在较大差别。 相似文献
6.
7.
8.
A. Basovich 《Dynamics of Atmospheres and Oceans》2011,51(3):151-164
The interaction between non-uniform near-surface currents and long surface waves is shown to produce large-scale secondary circulations. The circulations are caused by the Craik–Leibovich vortex force imposed on the existing non-uniform current by the surface waves. The current could be produced by different types of sources, such as by ship wakes or by river and sewer outflows. In this paper the circulations are considered for three representative types of currents: a near-surface jet, a shear current, and an underwater jet. A model similar to the model of Langmuir circulations is formulated and studied numerically. The general model takes into account the effect of viscosity on the main current as well as the effect of the circulation-related advection on the main current and secondary flow itself. A simplified model that describes the initial stage of the development of circulations was used in order to demonstrate the strength of the phenomenon and its dependence on some parameters of the problem. At this initial stage, the effect of viscosity on the main current as well as the effect of advection caused by the circulations was neglected (under assumption that the perturbation velocity is small). The effect of the viscosity on the circulations was included in the solution, and it was shown that initial development of the circulations is practically independent of the viscosity. This fact simplifies the solution of the problem and removes the uncertainty related to the value of the turbulent viscosity at the initial stage of the circulations. The results obtained demonstrate that strong circulations are generated under very realistic assumptions regarding the parameters of the current and the surface waves. The maximum velocity at the surface produced by such circulations can easily reach several centimeters per second. A circulatory flow with this magnitude of velocity at the surface can significantly affect short surface waves and, correspondingly, radar and optical signatures produced by the initial currents on the sea surface. Some important conclusions about the nature of these signatures are made based on numerical results and simple qualitative arguments. Theoretical predictions include, for example, the asymmetry of centerline ship wakes and the difference in the width and length between images of two wakes of similar ships moving in opposite directions when ambient surface waves are present. 相似文献
9.
Understanding of the temporal variation of oceanic heat content(OHC) is of fundamental importance to the prediction of climate change and associated global meteorological phenomena. However, OHC characteristics in the Pacific and Indian oceans are not well understood. Based on in situ ocean temperature and salinity profiles mainly from the Argo program, we estimated the upper layer(0–750 m) OHC in the Indo-Pacific Ocean(40°S–40°N, 30°E–80°W). Spatial and temporal variability of OHC and its likely physical mechanisms are also analyzed. Climatic distributions of upper-layer OHC in the Indian and Pacific oceans have a similar saddle pattern in the subtropics, and the highest OHC value was in the northern Arabian Sea. However, OHC variabilities in the two oceans were different. OHC in the Pacific has an east-west see-saw pattern, which does not appear in the Indian Ocean. In the Indian Ocean, the largest change was around 10°S. The most interesting phenomenon is that, there was a long-term shift of OHC in the Indo-Pacific Ocean during 2001–2012. Such variation coincided with modulation of subsurface temperature/salinity. During 2001–2007, there was subsurface cooling(freshening)nearly the entire upper 400 m layer in the western Pacific and warming(salting) in the eastern Pacific. During2008–2012, the thermocline deepened in the western Pacific but shoaled in the east. In the Indian Ocean, there was only cooling(upper 150 m only) and freshening(almost the entire upper 400 m) during 2001–2007. The thermocline deepened during 2008–2012 in the Indian Ocean. Such change appeared from the equator to off the equator and even to the subtropics(about 20°N/S) in the two oceans. This long-term change of subsurface temperature/salinity may have been caused by change of the wind field over the two oceans during 2001–2012, in turn modifying OHC. 相似文献
10.
In this paper, a heavy sea fog event occurring over the Yellow Sea on 11 April 2004 was investigated based upon observational and modeling analyses. From the observational analyses, this sea fog event is a typical advection cooling case. Sea surface temperature(SST) and specific humidity(SH) show strong gradients from south to north, in which warm water is located in the south and consequently, moisture is larger in the south than in the north due to evaporation processes. After fog formation, evaporation process provides more moisture into the air and further contributes to fog evolution. The sea fog event was reproduced by the Regional Atmospheric Modeling System(RAMS) reasonably. The roles of important physical processes such as radiation, turbulence as well as atmospheric stratification in sea fog’s structure and its formation mechanisms were analyzed using the model results. The roles of long wave radiation cooling, turbulence as well as atmospheric stratification were analyzed based on the modeling results. It is found that the long wave radiative cooling at the fog top plays an important role in cooling down the fog layer through turbulence mixing. The fog top cooling can overpower warming from the surface. Sea fog develops upward with the aid of turbulence. The buoyancy term, i.e., the unstable layer, contributes to the generation of TKE in the fog region. However, the temperature inversion layer prevents fog from growing upward. 相似文献