A SYNOPTIC CLIMATOLOGY OF MOISTURE STRESS GRADIENTS IN THE WESTERN GREAT LAKES REGION     

John A. Harrington Jr.  Jay R. Harman 《自然地理学》2013,34(1):43-56

Surface pressure distributions and 500 millibar flow patterns are identified for summer season days with a moisture stress gradient across the western Great Lakes region that may be related to the location of the prairie-forest ecotone. Results indicate that days with moisture stress gradients are a characteristic feature of the summer climate in the area and that these days are associated with unique, nonrandom groupings of mid-tropospheric flow patterns. SW-NE and W-E stress gradients, those that appear to contribute most to defining and reinforcing the location of the ecotone, occur most frequently, and the modal 500-mb flow direction for these transect groups, an azimuth of 290°, is the same as the mode for the entire population of summer season flow directions. We conclude that the modal mid-tropospheric circulation of the summer season plays a significant role in determining the surface weather conditions that regulate the most common moisture stress patterns within the western Great Lakes region.  相似文献   

The irony and the exclusivity of Atlantic bluefin tuna management     

D.G. Webster 《Marine Policy》2011

The eastern stock of Atlantic bluefin tuna (thunnus thynnus) was recently nominated for protection under the Convention on International Trade in Endangered Species of Flora and Fauna (CITES). That nomination failed, which leaves management of the heavily overfished stock in the hands of the International Commission for the Conservation of Atlantic Tunas (ICCAT). This paper reviews the history of ICCAT management of Atlantic bluefin tuna to show that (1) early elimination of competitive forces prevented agreement on management in keeping with scientific advice, resulting in the steep decline of the stock, (2) even just the threat of a CITES listing can provide temporary impetus for marked improvement in ICCAT management, and (3) long-term sustainable management by ICCAT will require continued economic and political pressure.  相似文献   

Spatial distribution of surgeonfish and parrotfish in the north sector of the Mesoamerican Barrier Reef System          下载免费PDF全文

Roberto C. Hernández‐Landa  Gilberto Acosta‐González  Enrique Núñez‐Lara  Jesús E Arias‐González 《Marine Ecology》2015,36(3):432-446

Surgeonfish and parrotfish play an important role in structuring the benthic communities of coral reefs. However, despite their importance, little is known about their distribution patterns in the north sector of the Mesoamerican Reef System. This study evaluated the distribution of these fish in 34 sites in four habitats (lagoon, front, slopes and terrace) along a depth gradient (c 0.5–20 m). These herbivorous fish were assessed by visual censuses. Species dominance was evaluated for each habitat using SIMPER analysis. Habitat characteristics data were collected to determine the relationship between habitat conditions and spatial variations in herbivorous fish (using abundance and biomass as a proxy) via redundancy analysis. The herbivorous fish assemblage had a low density (fish per 100 m²) and biomass (g·100 m^?2) in comparison with assemblages in similar studies. In contrast, species richness was high compared with other studies in the Caribbean. Spatial variation of the abundance, biomass and size of herbivorous fish was strongly related to coral and seagrass cover, as well as to depth and rugosity. These four variables were critical in controlling the distribution patterns of the herbivorous fish assemblages. No associations were found between fish and macroalgae or any other benthic group. The present study indicates that the species richness of surgeonfish and parrotfish was not regionally affected by the dominance of macroalgae in the habitats studied. Seagrass beds and the coral reef matrix need to be preserved for the herbivorous fish assemblages to remain healthy and capable of controlling excess macroalgae growth.  相似文献   

A review of the ecology and management of temporarily open/closed estuaries in South Africa,with particular emphasis on river flow and mouth state as primary drivers of these systems     

《African Journal of Marine Science》2013,35(2):163-180

Research in South African temporarily open/closed estuaries that includes studies on the hydrodynamics, sediment dynamics, macronutrients, microalgae, macrophytes, zoobenthos, hyperbenthos, zooplankton, ichthyoplankton, fishes and birds is used as a basis to review the ecology and management of this estuary type on the subcontinent. Particular attention is given to the responses of the different ecosystem components to the opening and closing of the estuary mouth and how this is driven by riverine and marine events, as well as anthropogenic influences. In addition, the wider implications of these research findings for the management of temporarily open/closed estuaries in terms of freshwater supply are explored, together with the role of government legislation in maintaining the ecological integrity of these important wetland systems.  相似文献   

基于形态对比和统计分析的中生代鸟类栖息行为的识别和判断     

张玉光  刘迪  李志恒  李岩  刘庆国 《地质论评》2010,56(6):875-885

鸟类栖息行为是鸟类重要的生活习性,与鸟类后肢骨骼的形态结构之间存在密切的适应演化关系,而中生代鸟类栖息行为的分析推断也是古鸟类学研究的热点。文中通过对大量现生鸟类的后肢骨骼系统进行形态学对比、统计学分析,分别以后肢3块骨骼的长度变化、跗跖骨远端跖骨滑车的特征差异、第Ⅲ趾趾节长度变化规律和第Ⅲ脚爪爪弧的弧度大小为研究对象,并与其对应的栖息行为分别进行分析判断,然后将判断特征和有效变量运用于中生代鸟类栖息行为的推理中。通过系统的分析研究,对中生代鸟类的栖息行为得出如下的推断:大量基干鸟类的栖息习性是以攀援为主,只有少数可以树栖生活,反鸟类的栖息习性十分接近树栖鸟类,今鸟类的栖息行为兼有树栖、地栖的习性。  相似文献   

A re-analysis of the marine bird Asiahesperornis from northern Kazakhstan     

Gareth J. Dyke  Dmitry V. Malakhov  Luis M. Chiappe 《Cretaceous Research》2006,27(6):947-953

Fossil bird material is exceptionally rare in the Mesozoic of western Asia. With the notable exception of the Upper Cretaceous foot-propelled diving bird Asiahesperornis bazhanovi from northern Kazakhstan, the only bird fossils described from this region have been bone fragments from the Upper Cretaceous of Uzbekistan. In this paper, all material referred to date to the hesperornithiform Asiahesperornis is reviewed and re-described. New postcranial elements of this taxon from the holotype Kushmurun locality (Maastrichtian Zhuravlovskaya Svita) are presented, and the taxonomic history and likely affinities of this ocean-going bird are discussed.  相似文献   

青岛胶州湾湿地水鸟资源现状及保护对策   总被引：1，自引：0，他引：1  

耿以龙  王希明  陈庆道  迟仁平 《湿地科学与管理》2006,2(2):45-48

胶州湾是山东半岛面积最大的河口海湾型湿地,湿地总面积约3.7万hm2,由于其特殊的地理位置和丰富的湿地生物资源,成为亚太地区水鸟迁徙的重要停歇地和越冬地。目前胶州湾湿地鸟类有12目26科156种,其中包括许多全球濒危和国家级重点保护种类。鉴于目前胶州湾的不断萎缩及湿地生物多样性和生态环境的不断破坏现状,为保护湿地水鸟资源,恢复胶州湾良好的生态环境,应尽早建立湿地自然保护区,开展水鸟资源的保护和湿地环境生态改造,为亚太地区候鸟的顺利迁徙提供良好的栖息地,推动青岛市自然保护区建设事业。  相似文献   

越冬浮游植物光合作用活性的原位研究   总被引：7，自引：3，他引：7       下载免费PDF全文

吴晓东  孔繁翔  曹焕生  张民  刘桂民  赵巧华 《湖泊科学》2007,19(2):139-145

水体中浮游植物在越冬期间数量少,关于湖泊中越冬浮游植物如蓝藻、绿藻、硅藻等浮游植物的光合作用活性情况少见报道.本实验通过Phyto-PAM(Pulse Amplitude Modulation)对最大光量子产量Fv/Fm(可变荧光和最大荧光之比)和快速光曲线的测定,结合显微镜镜检结果,并在室内进行了硫酸铜处理以及鲁哥氏液处理实验,对太湖、巢湖和玄武湖处于越冬期间的浮游植物进行了原位光合作用活性的研究.显微镜镜检结果表明太湖和玄武湖水体中以绿藻和硅藻为主,而蓝藻很少,巢湖水体中有大量蓝藻、绿藻和硅藻.Phyto-PAM在对玄武湖和太湖水样原位测定时未检测出蓝藻,而绿藻和硅藻有光合作用活性,其Fv/Fm在0.5左右;对巢湖的水体检测到的蓝藻、绿藻、硅藻都具有光合作用活性,其中绿藻和硅藻的Fv/Fm在0.5左右,蓝藻的Fv/Fm在0.3左右;用硫酸铜处理实验在巢湖水样中发现水体仅有硅藻活性(Fv/Fm下降至0.2左右),而用鲁哥氏液处理后无任何藻类光合作用活性.上述实验结果表明,即使处于越冬期间,以较多数量出现在水体中的蓝藻、绿藻和硅藻仍然具有较高的光合作用活性.  相似文献   

Distribution of trace elements in subcellular fractions of three aquatic birds   总被引：1，自引：0，他引：1  

Nam DH  Anan Y  Ikemoto T  Kim EY  Tanabe S 《Marine pollution bulletin》2005,51(8-12):750-756

This study investigated the subcellular distribution of Cu, Zn, Cd and Ag in liver of mallard (Anas platyrhynchos), spot-billed duck (A. poecilorhyncha) and great cormorant (Phalacrocorax carbo) to better understand metal fractionation and dynamics in avian liver. Most of the total Cu, Zn, Cd and Ag were present in hepatocytosol, and their concentrations increased with total hepatic levels in all the three avian species. Copper, Zn and Cd in hepatocytosol were present mostly in metallothionein fractions (MTs), and Cu and Cd contents in this fraction were positively correlated with hepatocytosol levels in all the species. Silver was observed mostly in both high-molecular weight and MT fractions in hepatocytosol in mallard and great cormorant, whereas it was present in both low-molecular weight and MT fractions in spot-billed duck, suggesting that distribution of Ag in the hepatocytosol was species-specific. The elution profile of metals in MT fractions revealed six metallic peaks in mallard and spot-billed duck, and three peaks in great cormorant, implying the presence of multiple MT isoforms in the liver of these avian species. The present study demonstrated that MTs are closely associated with metal regulation, especially Cu and Cd, in these three aquatic birds.  相似文献   

Seasonal changes in the feeding ecology of guillemots (Uria aalge) off north and east Scotland     

B.F. Blake  T.J. Dixon  P.H. Jones  M.L. Tasker 《Estuarine, Coastal and Shelf Science》1985,20(5):559-568

Stomach contents were examined from 750 guillemots collected at several sites in the northern North Sea. The dietary composition was compared between months and between localities in order to assess seasonal and geographical trends in feeding strategy.From March to August sandeels dominated the diet, but in September a changeover period occurred when clupeid and gadoid remains became increasingly frequent in the stomach contents. This situation persisted over the winter period, but the importance of the two fish families varied with area, clupeids being more important in more southerly samples and gadoids in the north. Dietary data were considered in relation to available fisheries information and to known guillemot distribution patterns.  相似文献