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831.
Based on the quasi-harmonic analysis of 11 d vector ocean currents obtained from two high frequency sur- face wave radars located at Zhujiajian Island and Shengshan Island, the spatial distribution characteristics of surface tidal currents in the open sea area to the east of the Zhoushan Islands of Zhejiang Province, China are studied. The following conclusions are drawn from the analysis: the tidal current pattern in the open sea area to the east of Zhoushan Islands is primarily regular semidiurnal, which is significantly affected by the shallow water constituents. The directions of the major axes of tidal current ellipses of M2 lie approx- imately in the NW-SE direction. With the increasing of distance away from the coast, the directions of the tidal current ellipses gradually shift toward the E-W direction. The tidal currents are mainly reversing cur- rents. The spatial distribution of probable maximum current velocities decreases gradually from northeast to southwest which is basically in accordance with the spatial distribution of measured maximum current velocities. The residual currents near the coast are larger than those far away from the coast. The directions of the residual currents are basically north by east, and the angle to the due north increases gradually with the increasing distance away from the coast. The topography shows a certain impact on the spatial distri- bution of shallow water constituents, the rotation of tidal currents, the probable maximum currents and the residual currents. 相似文献
832.
Throughout the shores of the world,a confluence of different sources of pollution is common,e.g.,through outlets releasing brine,industrial,and domestic sewage.In this study,we assessed whether a combined disposal of domestic sewage and brine altered the patterns of abundance and assemblage structure of subtidal macrofauna inhabiting sandy seabeds on the south coast of Gran Canaria(Canary Islands,NE Atlantic Ocean).Samples were collected in two surveys(May 2008 and January 2009)at three distances(0,15,and30 m)away from the discharge point.Macrofaunal abundances showed different patterns with varying proximity from the disposal point in the two surveys.In May 2008,lower abundances were observed at0 m(53.89±46.82 ind.)than at 15 m(120±91.7 ind.)and 30 m(283.89±189.33 ind.)away from the disposal point.In January 2009,however,higher abundances were observed at 0 m(131.33±58.69 ind.)than at 30 m(100±24.44 ind.)and 15 m(84.78±58.39 ind.)away from the disposal point.Significant differences in macrofaunal assemblage structure were found with varying proximity from the discharge point in both surveys.The effect of proximity from the disposal point was confounded by changes in sedimentary composition between surveys,which contributed to explain differences in macrofaunal abundances and assemblage structure with varying proximity from the discharge point.As a result,confounding drivers of macrofaunal assemblage structure,here,changes in sediment composition,accounted for changes in macrofaunal abundances and assemblage structure with varying proximity from a combined disposal point of brine and sewage. 相似文献
833.
《African Journal of Marine Science》2013,35(3):439-444
Breeding numbers of Laridae and other surface-nesting seabirds have been monitored at sub-Antarctic Marion Island since 1996/1997 and counts of breeding birds were made at nearby Prince Edward Island in December 2001 and December 2008. Four species are regular breeders at the islands: Subantarctic skua Catharacta antarctica, kelp gull Larus dominicanus, Antarctic tern Sterna vittata and Kerguelen tern S. virgata. The latter three species currently each have populations of below 150 breeding pairs at the islands. Kelp gull numbers appear to be relatively stable though they may have decreased since the 1980s. Kerguelen tern numbers decreased and then recovered at Marion Island, but numbers of the species have declined at Prince Edward Island and it maintains a tenuous foothold there. The small Antarctic tern population appears to be stable. 相似文献
834.
Coral bleaching indices and thresholds for the Florida Reef Tract, Bahamas, and St. Croix, US Virgin Islands 总被引:2,自引:0,他引:2
It is well established that elevated sea temperatures cause widespread coral bleaching, yet confusion lingers as to what facet of extreme temperatures is most important. Utilizing long-term in situ datasets, we calculated nine thermal stress indices and tested their effectiveness at segregating bleaching years a posteriori for multiple reefs on the Florida Reef Tract. The indices examined represent three aspects of thermal stress: (1) short-term, acute temperature stress; (2) cumulative temperature stress; and (3) temperature variability. Maximum monthly sea surface temperature (SST) and the number of days >30.5 °C were the most significant; indicating that cumulative exposure to temperature extremes characterized bleaching years. Bleaching thresholds were warmer for Florida than the Bahamas and St. Croix, US Virgin Islands reflecting differences in seasonal maximum SST. Hind-casts showed that monthly mean SST above a local threshold explained all bleaching years in Florida, the Bahamas, and US Virgin Islands. 相似文献
835.
Two US Virgin Islands marinas were examined for potential metal impacts by comparing sediment chemistry data with two sediment quality guideline (SQG) values: the ratio of simultaneously extractable metals to acid volatile sulfides (SEM-AVS), and effects range-low and -mean (ERL-ERM) values. ERL-ERMs predicted the marina/boatyard complex (IBY: 2118 microg/g dry weight total metals, two exceeded ERMs) would have greater impacts than the marina with no boatyard (CBM: 231 microg/g dry weight total metals, no ERMs exceeded). The AVS-SEM method predicted IBY would have fewer effects due to high AVS-forming metal sulfide complexes, reducing trace metal bioavailability. These contradictory predictions demonstrate the importance of validating the results of either of these methods with other toxicity measures before making any management or regulatory decisions regarding boating and marina impacts. This is especially important in non-temperate areas where sediment quality guidelines have not been validated. 相似文献
836.
南麂列岛海洋自然保护区浮游动物丰度和生物量的时空分布 总被引:4,自引:0,他引:4
根据2004年5月、8月、11月和2005年2月南麂列岛海洋自然保护区海域调查资料,阐述了该海域浮游动物丰度和生物量的时空分布,探讨了其与环境因子的关系,并分析了保护区建区14a后丰度和生物量的变化以及不同季节生态类群丰度的组成特点。结果表明,浮游动物丰度和生物量季节变化明显,8月丰度最高,为(267.05±100.94)ind./m3,其他依次为11月、5月和2月;5月生物量最高,为(403.64±331.41)mg/m3,其他依次为8月、11月和2月;相关性分析表明,浮游动物丰度与生物量之间存在明显的正相关,相关系数为0.763,丰度、生物量与水温呈显著的正相关;与无机氮、活性磷酸盐表现为负相关;与浮游植物细胞丰度和叶绿素a含量未表现出相关性;与1990年相比,2004年春季浮游动物丰度和生物量均有所下降,秋季变化不大;不同季节各生物类群丰度和百分比均有差异。 相似文献
837.
中国近海及其附近海域若干涡旋研究综述Ⅱ.东海和琉球群岛以东海域 总被引:2,自引:0,他引:2
综述东海和琉球群岛以东海域若干气旋型和反气旋型涡旋的研究.对东海陆架、200m以浅海域,主要讨论了东海西南部反气旋涡、济州岛西南气旋式涡和长江口东北气旋式冷涡.东海两侧和陆坡附近出现了各种不同尺度的涡旋,其动力原因之一是与东海黑潮弯曲现象有很大关系,其次也与地形、琉球群岛存在等有关.东海黑潮有两种类型弯曲:黑潮锋弯曲和黑潮路径弯曲.黑潮第一种弯曲出现了锋面涡旋,评述了锋面涡旋的存在时间尺度与空间尺度和结构等;也指出了黑潮第二种弯曲,即路径弯曲时在其两侧出现了中尺度气旋式和反气旋涡,讨论了它们的变化的特性.特别讨论了冲绳北段黑潮弯曲路径和中尺度涡的相互作用,着重指出,当气旋式涡在冲绳海槽北段成长,并充分地发展,其周期约在1~3个月时,它的空间尺度成长到约为200km(此尺度相当于冲绳海槽的纬向尺度)时,黑潮路径从北段转移到南段.也分析了东海黑潮流量和其附近中尺度涡的相互作用.最后指出在琉球群岛以东、以南海域,经常出现各种不同的中尺度反气旋式和气旋式涡,讨论了它们在时间与空间尺度上变化的特征. 相似文献
838.
泥火山是地球运动和深部含流体物质向表层迁移的一种重要形式, 其喷溢及喷出物对认识地质动力、地层岩性和资源环境具有重要的意义。东沙海区新生界薄(~1km), 中生界厚(>5km), 是南海最典型的中生代沉积区和油气勘探待突破区。区内有众多的海山海丘, 过去都被推测为不利于油气成藏的岩浆火山。但近年来针对这些海山进行的调查发现了大量海底地层底辟形变与断裂、流体充注空白反射带和喷溢释放结构。通过浅表层取样采获了丰富的自生碳酸盐岩结核及深水珊瑚、海绵等生物, 表明众多海山、海丘具有明显的泥火山活动特征。东沙泥火山的发现表明区内具有良好的油气生成和运移条件, 为勘探源于中生界的油气和水合物提供了重要线索; 而大量深水珊瑚和海绵的出现指示东沙泥火山区可能是深水珊瑚礁、海绵礁发育区, 为研究油气泄漏、化养生物和环境三者的关系提供了重要的研究对象。 相似文献
839.
Rolf Guttesen 《Geografisk tidskrift / udgivet af Bestyrelsen for Det Kongelige danske geografiske selskab》2013,113(2):81-91
The article deals with aspects of the historical geography of the Faeroe Islands in the 19th century with a focus on animal production, i.e. sheep and cows. It is based on material from the Regional Archive, Føroya Landsskjalasavn. The tithe lists showing the King's third from Norderöe district, 1801–1859, are analysed in detail and compared with the statements from another series of documents, the Sheriff s half-yearly reports on the state of the district. Together these two sets of records give a detailed picture of the development and variation in the number of cows, paying “butter-tithe” and the number of sheep slaughtered, paying “wool-tithe”. The number of cows surviving the winter, depended on the amount and quality of winter fodder or hay, which was produced in the infield the preceding summer. The sheep, on the other hand, that can survive the winter while grazing in the outfield, are dependent on the severity or mildness of the winter as well as their condition in the lambing period. The two series provide data on summer as well as winter weather conditions. The analysis makes an attempt, using the concepts known from the critical realist theory of science, to find the mechanisms as well as necessary and contingent conditions involved in the two processes. 相似文献
840.
中国海域辽阔,但公开发表和出版的1∶100万及更大比例尺的海底地貌图尚属空白。在综合研究已有的海底地貌分类系统的基础上,以南沙群岛郑和群礁幅为实验区,尝试建立了该海区1∶100万海洋地貌分类系统,利用历年来南沙群岛海区等深线图(1∶50万)、沉积图(1∶200万)、地质地球物理图集(1∶100万)及各种文献资料和在专家指导的基础上,绘制了该幅的海底地貌图并对该区域的地貌格局进行了分析。实验表明,通过对现有资料的综合进行1∶100万海底地貌制图是可行的。实验发现:1)等深线数据如同陆地上的等高线数据,是进行海底地貌制图的基本和主要数据源;2)海底底质和沉积物数据是进行海底地貌成因类型判别的重要依据;3)海底构造格局对海底地貌格局起着根本的控制作用,因此海底地质地球物理数据也是进行海底地貌制图不可或缺的数据之一。 相似文献