Reproductive characteristics of invasive gammarids in the Rhine-Main-Danube catchment, South Germany     

Axel Kley  Gerhard Maier   《Limnologica》2006,36(2):79-90

The gammarid composition at 25 sites in the rivers Danube, Main and the southern reaches of the Rhine were studied during the years 2002–2004. Dikerogammarus villosus and Echinogammarus ischnus were the most frequent species prevailing at 17 sites. Sympatric occurrence of D. villosus and E. ischnus was observed at 12 sites. Dikerogammarus haemobaphes was recorded at 7 sites; this species prevailed in the Danube, west of the Weltenburger Enge and in the Isar mouth where it co-existed with native species (Gammarus pulex and/or G. roeseli) at 6 sites. Dikerogammarus bispinosus and E. berilloni were found at only 1 site, where they co-existed with D. villosus and E. ischnus, and with D. villosus and native species, respectively. Investigation of reproductive characteristics at 3 sites showed that females of D. villosus and D. haemobaphes produced the biggest clutches with more than 100 eggs. Females of E. ischnus produced much smaller clutches (10–35 eggs on an average), but very big eggs. Clutch sizes and egg volumes of D. bispinosus and E. berilloni resembled those of native species. Our results suggest that the most successful invaders (D. villosus, D. haemobaphes and E. ischnus) display reproductive traits that facilitate their success. Both Dikerogammarus sp. allocate energy into production of many but small eggs, thus maximizing offspring number, while E. ischnus allocates its energy into production of fewer but large eggs which could be beneficial at sites where food is scarce.  相似文献   

The European Water Framework Directive 2000/60/EC in the evaluation of the ecological status of watercourses. Case study: the river Chienti (central Apennines,Italy)     

Stefania Scuri  Mariacristina Torrisi  Mario Cocchioni  Antonio Dell'Uomo 《洁净——土壤、空气、水》2006,34(5):498-505

The quality of the river Chienti (eastern‐central Apennines, Italy) has been evaluated according to the Water Framework Directive 2000/60/EC, taking into consideration both biotic (animal and vegetable) and chemical parameters. In studying the biotic component, two indices were used: the E.B.I, Extended Biotic Index (version adapted to the Italian rivers), based on macroinvertebrates, and the EPI‐D, the Eutrophication and/or Pollution Index, based on diatoms. For both macroinvertebrates and diatoms, two samplings were conducted, one in June and the other in October 2003. Instead, according to the Italian Law 152/99 the chemical and bacteriological analyses were conducted monthly for the entire year. The results of biomonitoring and chemical‐bacteriological analyses unanimously demonstrated a good ecological situation for the upper section of the Chienti, though the situation tends to worsen as the river continues its descent and undergoes increased anthropogenic pressure. Data obtained were correlated with Spearman's coefficients and principal component analysis. Both statistical calculations showed clear, direct correlation between the two biotic indices and an inverse correlation between these and the chemical and bacteriological parameters. However, a few differences of judgement that emerged among the various indices highlight the importance of using them simultaneously in order to obtain a more accurate diagnosis of the ecological status of the watercourses.  相似文献   

大连市近岸海域水环境质量及影响因素分析   总被引：5，自引：0，他引：5       下载免费PDF全文

盖美  王本德 《水科学进展》2003,14(4):454-458

大连是中国北方沿海重要的中心城市和旅游城市,近年来,由于经济的发展,废水排放量的增加,近岸海域水质恶化已成为大连市主要的生态环境问题.采用模糊模式识别模型对大连市近岸海域进行水质评价,研究近岸海域水环境动态变化及影响因素分析,提出了水环境改善措施.  相似文献   

水分胁迫下棉花冠层叶片氮素状况的高光谱估测研究   总被引：4，自引：3，他引：4  

马亚琴  包安明  王登伟  孙莉  黄春燕  冯宪伟  肖春华  杨新军 《干旱区地理》2003,26(4):408-412

在不同灌水量条件下，对棉花单叶叶绿素含量和单叶全氮含量做相关分析，并采用地物光谱仪。获取北疆棉花冠层关键生育时期的高光谱数据。应用一阶微分光谱，衍生出基于光谱位置变量的分析方法。以红边积分面积(SDr)为白变量，冠层全氮(TN)含量为因变量，做相关分析。结果表明：叶绿素含量与TN含量呈显著的正相关(R=0．8723^**。n=39)，叶绿素含量能有效的估计棉花单叶TN含量；红边积分面积变量与冠层TN含量呈显著的相关性，相关系数是0．7394^**(n=40)，利用构建的相关模型可以较为精确地估测新陆早6号、8号冠层叶片的全氮含量，RMSE分别为0．3859和0．4272。研究认为红边积分面积变量具有预测棉花冠层全氮含量的应用潜力。  相似文献   

ON THE RELATIONSHIP BETWEEN PRECIPITATION ANOMALIES IN THE FIRST RAINING SEASON (APRIL-JUNE) IN SOUTHERN CHINA AND SST OVER OFFSHORE WATERS IN CHINA   总被引：5，自引：2，他引：5  

邓立平  王谦谦 《热带气象学报(英文版)》2002,8(1):75-84

Precipitation anomalies in the first raining season of southern China were analyzed, with the suggestion that there are obvious interannual variation of peak values. In the raining season, the general tendency of precipitation is not obvious and the anomalous oscillation is multi-scale. Corresponding to years of more or less precipitation in the raining season, there are sharply opposite distribution across the nation in the simultaneous periods. In addition, by studying the distribution of correlation between anomalous precipitation in southern China in the first raining season and SSTA over offshore waters of China in the preceding period (June ~ August of the previous year), a sensitive zone of waters has been found that has steady effect on the precipitation of southern China in the season. Discussions are also made of the sensitive period, its simultaneous SSTA and subsequent anomalous circulation field in relation to precipitation anomalies and simultaneous circulation field in the first raining season of southern China. In the last part of the work, relationship between the SSTA in the sensitive zone and global SSTA is analyzed. A possible mechanism by which SSTA in offshore Chinese waters affects the precipitation anomalies in the first raining season of southern China is put forward.  相似文献   

由等高线计算水域体积   总被引：3，自引：1，他引：2  

王延亮  王宝山 《测绘工程》1999,8(3):52-55

介绍由等高线计算水域体积的过程,分析了水下地形的特点,对应注意的问题进行了讨论并给出了解决方案和算法。  相似文献   

氟的水文地球化学   总被引：3，自引：0，他引：3  

孙占学 《华东地质学院学报》1992,15(3):288-295

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Comparisons between the ichthyofaunas of a temperate lagoonal-like estuary and the embayment into which that estuary discharges     

I. C. Potter  D. Tiivel  F. J. Valesini  G. A. Hyndes 《International Journal of Salt Lake Research》1996,5(4):337-358

Leschenault Estuary consists of a large lagoonal-like water body, which opens into Koombana Bay through a short and deep entrance channel at its southern end. Since the only major tributary discharges into the estuary opposite the entrance channel, much of the freshwater discharge in the winter passes directly out to sea. Consequently, during the year of the present study, the mean monthly salinities in the main body of the estuary remained above 20 per mil. This presumably accounts for the fact that the ichthyofaunal composition in the shallows of the estuary did not undergo the type of marked changes that are exhibited in other south-western Australian estuaries, in which salinities often fall below 10 per mil in winter. Despite the maintenance of high salinities in Leschenault Estuary and a close proximity to Koombana Bay, the estuary contained a far greater density and markedly different species composition of fish than that found in that marine embayment. This difference reflected, in part, the high abundance in Leschenault Estuary of some species whose entire life cycle is confined to estuaries,e.g. the atherinidsAtherinosoma elongata andLeptatherina wallacei and the gobiesPseudogobius olorum andAfurcagobius suppositus, and the fact that the juveniles of several marine species,e.g. Hyperlophus vittatus, Sillaginodes punctata, Mugil cephalus andGymnapistes marmoratus were also largely or entirely restricted to the estuary. In contrast,Lesueurina platycephala, which was by far the most abundant species in Koombana Bay, was absent in the estuary. Furthermore, the relatively protected region of Koombana Bay contained a greater density and different composition of fish than the more exposed region of this embayment. This reflected the greater use that was made of the protected region as a nursery area by certain marine species,e.g. Aldrichetta forsten andSillago bassensis. Our data, when taken in conjunction with those collected on the fish fauna in other south-western Australian estuaries, demonstrate that, within this geographical region, some fish species are specifically adapted to the estuarine environment, and that certain marine species apparently have a strong preference for using the highly protected and productive waters of this type of environment as a nursery area.  相似文献   

论太平洋水体中元素行为的周期性     

于升松 《盐湖研究》1994,2(2):11-19

尽管海洋水及自生矿物相的复杂性，但我们仍发现了：１．周期表中的绝大多数元素在海洋铁锰结核氧化物中的富集程度Ｋｐ、在海水中的滞留时间τ，以及在氧化物相中的晶格能ｕ三参数间存在非常好的相关性；２．该三参数各自随元素原子序数的增加而展示出了好的化学周期性；３．晶格能ｕ是控制化学元素在海洋中的行为和迁移等性质的一极其重要参数．  相似文献   

The effect of hydrochemical factors on the dissolution rate of gypsiferous rocks in flowing water     

Ana Navas 《地球表面变化过程与地形》1990,15(8):709-715

In order to investigate the rate of dissolution of gypsiferous rocks under natural conditions in streams of the Ebro river basin, 55 dissolution trials were carried out with spheres of alabastrine gypsum placed in flowing water. Experimental conditions involved flow velocities between 0·3 and 1·2 m s^?1, electrical conductivities between 0·3 and 1·9 dS m^?1, and the saturation indices of gypsum between ?2·1 and ?0·33. Mean values of dissolution rate obtained vary from 104 to 226 gm^?2 h^?1. This loss of mass corresponded to a volume of gypsum of between 393 and 853mmm^?2 year^?1. The factors most affecting the dissolution of gypsum are in descending order of importance: flow velocity > electrical conductivity > gypsum saturation.  相似文献