Short-term stability of genetic structure in populations of the sea anemone Metridium senile

Populations of the sea anemone Metridium senile (L.) were sampled from several locations in eastern North America in two series, one collected from 1977–1979 and the other from 1981–1985. Fourteen populations were sampled twice at one- to six-year intervals. Samples were analyzed for temporal differences in genetic composition at both the single locus and multiple locus levels. Overall patterns of geographic variation in allele frequency did not change between series. Regressions describing clines did not differ significantly, and loci not showing clinal variation in the first series remained similar in the second. Analysis of populations sampled twice produced no systematic evidence of change in allele frequency with time for any of four polymorphic loci. Comparisons with computer simulations of repeated sampling of multiple locus genotypes from panmictic populations with free recombination also revealed little temporal change at this level. One population showed possible evidence of recruitment from a different gene pool. Other significant departures from expectations reflected more reproducibility of genotype distributions between samples than expected for sexual populations. This excess stability likely results jointly from clonal reproduction and little sexual recruitment. Despite these indications of genetic stability in adult populations, newly settled juveniles were genetically different from resistant adults in one population, demonstrating the potential for genetic change by immigration. Successful sexual recruitment seems to be rare, even though larvae regularly settle from the plankton. Although interpretation of these results is somewhat limited by lack of knowledge of longevities and generation times, to the extent that they reflect longer-term trends, they suggest that at least some of the observed patterns of geographic variation in allele frequency probably result from natural selection.     

Grenzüberschreitender Seeuferschutz im Spannungsfeld von Nutzungsinteressen am Beispiel Bodensee (Teil 1)

The shores of many Central European lakes located in the hinterland of large conurbations are heavily endangered by intensive settlement, traffic, sewage input, manipulation of the water level, tourism and recreation. This increasing impact has negatively affected the function of the lake shore in respect to conservation and species protection, to water protection and its importance for recreation. This paper describes the overlap of the multiple uses and the precautions planned since 1981 on the national and international level to guarantee the essential multiple functionality, e.g. as drinking water reservoir for the conurbations in the northern part of Baden-Württemberg, as supraregional centre for water sports and tourism, and as an important environment for endangered plant and animal species. Management measures include regional planning as well as the international water protection and preservation with many contributions from non governmental international organisations. Given a high agreement concerning these aims, many indispensable actions could successfully be realised on the political and administrative level. On the basis of 14 topics we follow the development since 1981, most recently also driven by the EU (FFH Natura 2000, Water framework directive). Backlogs became obvious for four topics: 1. The lack of efficient reviews on completed measures, 2. gaps in basic understanding, 3. The dragging harmonisation of an integrated shore protection program across the borders, and 4. the lack of concepts for a sustainable development including plans for monitoring.     

聚硅氯化铝(PASiC)混凝剂的特性及絮凝动态过程

 采用共聚与复合两种制备工艺,分别制备出具有不同碱化度(B)和不同Al/Si摩尔比系列的商用聚硅氯化铝(PASiC)混凝剂,并分别采用颗粒粒径测定方法和流动电流(SC)测定技术研究比较了PASiC和聚合氯化铝(PAC)混凝剂的颗粒大小、电动特性和凝聚絮凝动态过程.结果表明,Al/Si摩尔比、B值和制备工艺影响PASiC的聚合和带电特性.Al/Si摩尔比越小和B值越大,PASiC的颗粒就越大;在相同的B值下,PASiC较PAC具有更大的颗粒粒径.PASiC的电中和能力较PAC有所下降,且Al/Si摩尔比越小,PASiC的电中和能力下降越多;与PAC相比,PASiC具有更快的凝聚絮凝速度和形成更大的絮体;且Al/Si摩尔比越小,PASiC形成的絮体就越大.     

A method for assessing generalised nitrogen leaching estimates for agricultural land

The purpose of this study was to develop a method for assessing generalised N leaching estimates from large areas of agricultural land. The system developed was based on calculating a number of N leaching estimates for different typical cropping situations. The estimates were normalised with respect to varying weather conditions and crop production. The different cropping situations were described by setting up a matrix consisting of crucial factors influencing leaching such as soils, crops and climate. Nitrogen leaching was then estimated for a number of combinations of these factors. Calculations were made for three different regions where all the major crops were cultivated on soils with seven different textures and four different organic-N classes and two fertilisation regimes. The three regions are representative of climates and agricultural practices in some of the major agricultural areas in Sweden. The model used was the SOILN model. Leaching of nitrogen from the root zone showed large variations. The range was from 1 to 50 kg ha⁻¹ for different soils and crops when only fertiliser N was applied. Leaching varied both due to different climates and differences in cultivation practices between the regions. Leaching decreased in a south-north gradient. Leaching increased as a result of greater mineralisation when the organic matter content in the soils was increased, leaching was less from soils with a high clay content and was very small for the heavy clay soil. This revised version was published online in July 2006 with corrections to the Cover Date.     

Evaluation of a novel structural model to describe the endogenous release of lead from bone

The aim of this paper was to assess the endogenous release of lead from bone to blood, in 204 exposed subjects. resuming their duties after a 10-month strike in a primary lead smelter in 1991. In vivo 109Cd K X-ray Fluorescence (109Cd K XRF) was used to measure the bone lead concentration in tibia and calcaneus in the smelter, in 1994 and five years later. The 1994 data were used to derive the post-strike bone lead concentrations retrospectively from the significant association between bone lead and the cumulative blood lead index (CBLI). When a linear model was used to predict the current blood lead upon the level of lead in bone, structural analysis of the data produced slopes for tibia (2.0, 95% CI 1.66-2.54) and calcaneus (0.19, 95% CI 0.16-0.23) that were significantly higher than those predicted by the commonly used simple linear regression method, for tibia (0.73, 95%, CI 0.58-0.88) and calcaneus (0.08, 95% CI 0.06-0.09). This suggests that more lead than previously predicted by regression is released from bone to blood. Furthermore, the structural analysis of the data produced an estimation of the contribution of the bone lead stores to the bloodstream that was more consistent with the 1999 epidemiological data than did the regression estimation. Moreover, a non-linear relationship between tibia lead and blood lead was suggested from the assumption checking procedures for regression. When a non-linear regression model was fit to the data, the method produced estimates of important parameters in human lead kinetics, namely the blood lead saturation constant, showing a good agreement with current knowledge of lead metabolism. Finally, the likelihood of a non-linear bone lead release seems to be supported by the recently described dependence of the half-life of lead in bone on age and intensity of occupational exposure.