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761.
Overview of integrative tools and methods in assessing ecological integrity in estuarine and coastal systems worldwide 总被引:9,自引:1,他引:8
Borja A Bricker SB Dauer DM Demetriades NT Ferreira JG Forbes AT Hutchings P Jia X Kenchington R Carlos Marques J Zhu C 《Marine pollution bulletin》2008,56(9):1519-1537
In recent years, several sets of legislation worldwide (Oceans Act in USA, Australia or Canada; Water Framework Directive or Marine Strategy in Europe, National Water Act in South Africa, etc.) have been developed in order to address ecological quality or integrity, within estuarine and coastal systems. Most such legislation seeks to define quality in an integrative way, by using several biological elements, together with physico-chemical and pollution elements. Such an approach allows assessment of ecological status at the ecosystem level ('ecosystem approach' or 'holistic approach' methodologies), rather than at species level (e.g. mussel biomonitoring or Mussel Watch) or just at chemical level (i.e. quality objectives) alone. Increasing attention has been paid to the development of tools for different physico-chemical or biological (phytoplankton, zooplankton, benthos, algae, phanerogams, fishes) elements of the ecosystems. However, few methodologies integrate all the elements into a single evaluation of a water body. The need for such integrative tools to assess ecosystem quality is very important, both from a scientific and stakeholder point of view. Politicians and managers need information from simple and pragmatic, but scientifically sound methodologies, in order to show to society the evolution of a zone (estuary, coastal area, etc.), taking into account human pressures or recovery processes. These approaches include: (i) multidisciplinarity, inherent in the teams involved in their implementation; (ii) integration of biotic and abiotic factors; (iii) accurate and validated methods in determining ecological integrity; and (iv) adequate indicators to follow the evolution of the monitored ecosystems. While some countries increasingly use the establishment of marine parks to conserve marine biodiversity and ecological integrity, there is awareness (e.g. in Australia) that conservation and management of marine ecosystems cannot be restricted to Marine Protected Areas but must include areas outside such reserves. This contribution reviews the current situation of integrative ecological assessment worldwide, by presenting several examples from each of the continents: Africa, Asia, Australia, Europe and North America. 相似文献
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764.
Delayed baroclinic response of the Antarctic circumpolar current to surface wind stress 总被引:2,自引:0,他引:2
The Antarctic Circumpolar Current (ACC) responds to the surface windstress via two processes, i.e., the instant barotropic process and the delayed baroclinic process. This study focuses on the baroclinic instability mechanism in ACC, which was less reported in the literatures. Results show that the strengthening of surface zonal windstress causes the enhanced tilting of the isopycnal surface, leading to more intense baroclinic instability. Simultaneously, the mesoscale eddies resulting from the baro- clinic instability facilitate the transformation of mean potential energy to eddy energy, which causes the remarkable decrease of the ACC volume transport with the 2-year lag time. This delayed negative cor- relation between the ACC transport and the zonal windstress may account for the steadiness of the ACC transport during last two decades. 相似文献
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766.
Supported by the technologies of remote sensing (RS) and geographical information system (GIS), we chose northwest of Beijing as a study area and gave priority to understanding of the spatial-temporal characteristics of landscape pattern change through visually interpreted Landsat TM images of 1989, 1996 and 2005. It is believed that there were a series of landscape ecological problems caused by city expansion: landscape ecological connectivity was low; landscape structure was simplified; the fragmentation of green land patch was more obvious on the plain areas, moreover, spatial distribution of green land was unbalanced. For this reason, this study adopted accumulative cost distance model, combined with ecosystem services and spatial interactions of landscape types, analyzed the spatial difference of the ecological function and the compactness of landscape structure in the study area, and further discussed the landscape pattern optimization proposal. We find that it is essential to protect and establish ecological sources, to establish urban ecological corridors, and to establish ecological nodes at the landscape ecological strategic positions so as to intensify spatial relationships among landscape elements and maintain continuity of landscape ecological process and pattern in the course of city expansion. The methods and final results from this study are expected to be useful for landscape ecological planning in Beijing region. 相似文献
767.
文中以东昆仑断裂带周围分布的27个GPS站点的地壳运动速率矢量为约束,利用半无限弹性空间三维断裂位错模型,反演了东昆仑断裂、柴达木盆地北缘断裂、玛尼-玉树断裂和玛尔盖茶卡断裂带在2001年昆仑山口西MS8.1地震之前的运动速率,并认为这些断裂带以反演出的运动速率错动所形成的形变场可以作为震前的背景地壳形变场。基于这一具有构造意义的背景速度场资料,计算了区域地壳应变率场和地震矩累积率场。结果表明,昆仑山口西地震前,东昆仑断裂的东西大滩段和玛尼-玉树断裂西段为该区域2个最显著的地震矩累积率高值区,其中东昆仑断裂的东西大滩段高值区为后来的昆仑山口西MS8.1地震的发震段 相似文献
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769.
770.
通过对2007年6月3日滇西南宁洱6.4级地震前地震活动和前兆异常跟踪,震前对该地震作了短期预测.宁洱6.4级地震前,云南和滇西南地区的6级、5.8级以上地震出现了长时间的平静,显示了能量的积累过程;中期阶段4.5~5.0级地震在震中区周围形成了地震密集区,中、短期阶段滇西南地区MS≥3地震活动显著增强并形成空区,空区长轴250 km,计算震级为6.37,这与实际发生地震震级完全一致.滇西南地区的前兆异常显示,距离震源区近的以趋势异常为主,外围异常以突变为主. 相似文献