Long-term changes of zoobenthic fauna and submerged vegetation in the shallow Lake Monterosi (Italy)     

Luciana Mastrantuono  Teresa Mancinelli 《Limnologica》1999,29(2):160

Benthic invertebrates and aquatic vegetation were investigated in the volcanic Lake Monterosi with the aim to define the stage of development reached during progressive modifications which occurred in the shallow lake. Increasing trophy and introduction of an exotic plant (Nelumbo nucifera) were the key-factors responsible for the rapid qualitative reduction of the macrophyte population and its modification to non rooted plants (Ceratophyllum demersum). The invertebrate fauna associated with macrophytes was found to be abundant, diversified (83 taxa) and characterized by high diversity and presence of bioindicators of mesotrophy. Although the zoobenthic community appeared to be positively influenced by the macrophyte-dominated stage, some negative effects of Nelumbo-colonization on the invertebrate fauna indicated that further growth of this plant would cause a rapid change in the lake.  相似文献   

一次冷涡过程降水的微物理机制分析   总被引：6，自引：0，他引：6  

陈文选  王俊  刘文 《应用气象学报》1999,10(2):190-198

该文分析了一次冷涡天气过程中云微物理量的分布特征、降水粒子的增长机制及云下雨滴的蒸发效应。主要结果为:云系由低层暖性Sc云和冷性主体As云组成。As云底高2 km,云顶高大于5 km,云中存在比较大的过冷水区,–11.2 ℃时的过冷水含量0.21 g·m-3,但过冷水的含量分布极不均匀,大于0.05 g·m-3的过冷水区连续分布的宽度87%小于2.4 km,不利于云中冰晶的连续凇附增长;同时云下雨滴的蒸发效应大,直径小于1.0 mm的雨滴难以落到地面,因此本次过程只产生弱的降水。  相似文献   

Forced regression and its sedimentary response to continental lacustrine rift basin: A case of the Member 3 of Shahejie Formation in Laizhouwan sag,Bohai Bay Basin          下载免费PDF全文

Qin Yi  Zhu Xiao-Min  Wang Tong  Guo Cheng  Xie Shuang-Hui 《古地理学报》1999,22(3):457-468

Falling stage systems tract(FSST)is an offlap strata with strong relationship with hydrocarbon exploration,which is driven by relative lake-level fall and developed above the highstand systems tract and below the lowstand systems tract of a new sequence. It has no relationship with sediment supply. Based on the theory of sequence stratigraphy and sedimentology,3D seismic data,drilling core data,and well-logging data were comprehensively analyzed. The study showed that the FSST strata was formed in the Member 3 of Shahejie Formation in the Laizhouwan sag. The FSST can be divided into three units,namely as units P1,P2,and P3 from bottom to top. The P1 is the first unit of progradation downlap the bottom of the FSST. The top of the unit P3 is a sequence boundary exhibits subaerial unconformity. The seismic profile along the source direction is characterized by the low-angle oblique progradation reflection that downstream the center of lake basin from west to east. Incised valleys developed on the top of the FSST perpendicular to the source direction. Gamma-ray logging response is manifested by a series of funnel-shaped complex,indicating that the sedimentary response of the FSST was a cycle of coarsening-upward parasequence sets. Comprehensive studies on core interpretation and well-logging analysis showed that the FSST was a fluvial-delta sedimentary system with slumped fan deposits associated with the delta front. Consequently,the FSST is a common result of relative dry climate and falling of lake level,considering regional tectonic evolution,sediment supply,and paleo-climate change. The discovery of the FSST in the Laizhouwan sag has an important geological significance for the sedimentological interpretation,and it offers a guidance for further oil exploration in the study area. In addition,it also serves as a significant reference for future research on the FSST development and exploration in the continental lacustrine rift basin.  相似文献   

中国南方东部震旦纪碎屑岩和泥质岩成岩作用     

杜森官 《安徽地质》1999,(4)

中国南方震旦纪碎屑岩的成岩作用主要有压实和压溶、胶结和固结、重结晶、交代作用及自生矿物形成等,泥质岩的成岩作用主要为压实作用和成岩过程中粘土矿物的转化。其成岩过程可分为同生、成岩、后生、表生四个成岩作用阶段。在沉积盆地演化的不同阶段和处在盆地的不同部位,出现了不同的岩石类型,往往呈现各自的成岩作用变化特点。  相似文献   

景洪5.1,5.5级地震地下水动态预报启示   总被引：2，自引：0，他引：2  

夏菲 《地震研究》1999,22(3):243-250

本动态追踪了１９９７年景兴５．１、５．５级中强震的孕震－发震的整个过程,异常阶段属性清楚,异常发展层次分明,有动态感,过程清晰完整,表明中强地震亦有孕震过程。震前异常阶段的属性和异常的准同步是地震预测的主要依据。跟踪各类异常,掌握地震孕育发展的进程,把握时机有可能预报一些地震。本是“八五”、“九五”攻关成果运用的结果之一。  相似文献   

THE 1998 FLOOD OF THE YANGTZE RIVER     

ZHOU Wenhao  CHEN Yuchong 《国际泥沙研究》1999,(4)

1INTRODUCTIONDuringthefloodseasonof1998,anothercatastrophicfloodoccurredinthemiddleandlowerYangtzeRiverfollowingthecatastrophicfloodin1954.Ascomparedwiththe54flood,the1998floodwascharacterizedbythefactsthatthedurationofthehighwaterstagewasmuchlonger,thefloodcontrolwasmuchmoredifficult,andthetotalmanpowerandmaterialresourcesexpelldedintilefloodfightingweremuchmoreenormous.TOsummarizetheexperienceandlessonsfromthefloodissignificanttotilehydraulicengineeringandfloodcontroloftheYangtzeRiver.…  相似文献   

鲈鱼苗烂鳃、烂尾病病原菌的研究   总被引：9，自引：2，他引：7  

肖慧  李军  王祥红  纪伟尚  徐怀恕 《中国海洋大学学报(自然科学版)》1999,(1)

１９９７年４～５月,对花鲈（Ｌａｔｅｏｌａｂｒａｘｊａｐｏｎｉｃｕｓ）鱼苗期细菌性烂鳃和烂尾病的病原菌进行了研究。从具有明显症状的病鱼的病灶组织分离到２株致病菌Ｃ－１和Ｗ－１,经人工感染及从人工感染发病鱼体再分离的Ｗ－４和Ｗ－５菌株的再感染试验结果表明,所分离的细菌为鲈鱼苗烂尾,烂鳃病的致病菌。经６４项生物学特性,生理生化特征测试结果表明,这４株菌可归为一类,同属于鳗弧菌（Ｖｉｂｒｉｏａｎｇｕｉｌａｒｕｍ）。药敏试验结果表明,痢特灵、ＣＩＮ１００、ＭＥＬ２５、呋喃妥因、氯霉素、磺胺药＋ＴＭＰ和美洛西林等７种药物对病原菌有显著的抑制作用。  相似文献   

9711号台风对太湖水位影响分析   总被引：2，自引：0，他引：2  

闻余华  秦伯强 《湖泊科学》1998,10(4):91-94

针对１９９７年８月出现的９７１１号台风,就其对太湖水位的影响作了分析,分析表明,这次台风对太湖东西两岸水位影响显著东岸以减水为主,水位降幅达０．６６－０．９３ｍ,西岸以增水为主,增幅达０．６７－０．７７ｍ,水位振幅达－０．６７－１．２２ｍ,同一时间内,东西两岸水位差达１．１７－１．４２ｍ。分析还表明,太湖风场变化与水位变化关系较为紧密,表现为：当风向相对一致时,背风岸望亭,胥口的水位随风速的增加而  相似文献   

全新世艾比湖流域不同时段降水量的估算   总被引：7，自引：0，他引：7  

吴敬禄  王洪道  王苏民 《湖泊科学》1993,5(4):299-306

本文应用水热平衡模型,对艾比湖全新世时期三个高湖面期的降水量进行计算。结果表明,2ka—3ka B.P.降水量比现今高出9％,达到287mm/a;4.5ka—6ka B.P.增加16％,达到306mm/a;6.5ka—8.0ka B.P.增加了22％,达到322mm/a。  相似文献   

冲绳海槽现代张裂的地球物理特征   总被引：3，自引：0，他引：3  

杨文达 《海洋地质与第四纪地质》2004,24(3):77-82

位于东海陆架与琉球岛弧之间的冲绳海槽为板块俯冲作用形成的弧后断陷盆地,具有独特的构造地貌特征。自中新世末以来历经了4个强烈拉张的演化时期,目前已达到张裂的高级阶段。地球物理资料显示,海槽中的现代拉张作用仍在进行,表现在海槽轴部快速沉降形成地堑槽,对称分布的张性断裂,晚更新世—全新世以来的岩浆活动,从老至新排列的磁异常务带以及高地热流、频繁的地震活动等,充分体现了冲绳海槽的现代扩张特点。  相似文献