Patchiness in a Large Floodplain River: Associations Among Hydrology,Nutrients, and Fish Communities

Large floodplain rivers have internal structures shaped by directions and rates of water movement. In a previous study, we showed that spatial variation in local current velocities and degrees of hydrological exchange creates a patch‐work mosaic of nitrogen and phosphorus concentrations and ratios in the Upper Mississippi River. Here, we used long‐term fish and limnological data sets to test the hypothesis that fish communities differ between the previously identified patches defined by high or low nitrogen to phosphorus ratios (TN:TP) and to determine the extent to which select limnological covariates might explain those differences. Species considered as habitat generalists were common in both patch types but were at least 2 times as abundant in low TN:TP patches. Dominance by these species resulted in lower diversity in low TN:TP patches, whereas an increased relative abundance of a number of rheophilic (flow‐dependent) species resulted in higher diversity and a more even species distribution in high TN:TP patches. Of the limnological variables considered, the strongest predictor of fish species assemblage and diversity was water flow velocity, indicating that spatial patterns in water‐mediated connectivity may act as the main driver of both local nutrient concentrations and fish community composition in these reaches. The coupling among hydrology, biogeochemistry, and biodiversity in these river reaches suggests that landscape‐scale restoration projects that manipulate hydrogeomorphic patterns may also modify the spatial mosaic of nutrients and fish communities. Published 2016. This article is a U.S. Government work and is in the public domain in the USA.     

CONSEQUENCES OF THE PHYSICAL MANAGEMENT OF AN INVASIVE ALIEN PLANT FOR RIPARIAN PLANT SPECIES RICHNESS AND DIVERSITY

Management methods to control or eradicate invasive alien species should be guided by research into their efficacy in relation to the target species as well as their wider effects on the community. Impatiens glandulifera Royle (Balsaminaceae) is an invasive alien species, which has spread rapidly across Europe and North America, particularly colonizing riverbanks, wet woodlands, and wastelands. The effectiveness of two mechanical control measures and their impacts on community plant species richness and diversity within the riparian zone of the urban river Brent, London, England, was assessed. Over 2 years, an experiment was performed across three sites that exhibited contrasting levels of invasion of I. glandulifera: high, moderate and low. The experiment involved three treatments on replicated plots at all three sites: pruning at 6‐week intervals, weeding at 6‐week intervals, and a control. The effects of these control measures were most clearly seen at the site with the highest level of invasion and, to a smaller extent, at the moderately invaded site. Weeding was more successful in controlling the species than pruning, and the greatest impact of these treatments on community plant species richness and diversity was only apparent after 2 years of the experiment. Although seedlings of 10 other alien species were found, there was no evidence that their presence on the plots was detrimental to native species during the experimental period. Three common native species each approached 10% cover on the weeded plots at the heavily invaded site by the end of the experiment: Poa annua, Rumex obtusifolius, and Urtica dioica. These assessments provide guidance for implementing mechanical control of I. glandulifera in riparian zones. Copyright © 2012 John Wiley & Sons, Ltd.     

Surface properties and behaviour on abiotic surfaces of Staphylococcus carnosus, a genetically homogeneous species

This work aimed to characterize the surface properties of Staphylococcus carnosus and the influence of different media on their ability to adhere and grow on industrial supports. As their colonization could be dependant of the strain, the genetic diversity of the strains was studied. The diversity of 13 strains analysed by pulsed-field gel electrophoresis revealed that the S. carnosus strains formed a homogeneous genetic group. Their surface properties, characterized by studying their affinity to solvents, were hydrophilic with a strong negative surface charge. The S. carnosus strain CIT 833 hardly adhered to polytetrafluoroethylene (PTFE) and stainless steel chips. Tryptic soy broth (TSB) was the most favourable medium for growth on stainless steel support while TSB/NaCl was better for growth on PTFE. Scanning electron microscopy (sem) showed that this strain weakly colonized both supports and did not form cell aggregates. Indeed, the strain did not synthesize polysaccharides. These results showed that S. carnosus adhered on different abiotic surfaces which are used in food factories but was not able to accumulate on these surfaces. The inability of S. carnosus to form biofilm could explain why S. carnosus is rarely isolated in meat processing environment.     

不同部位后火低温大曲真菌群落结构比较分析

该研究以真菌内转录间隔区（internal transcribed spacer,ITS）为靶点,采用Illumina MiSeq高通量测序技术对后火低温大曲曲皮和曲心的真菌多样性进行分析。经α多样性发现,后火低温大曲曲心的真菌群落丰富度和多样性均显著高于曲皮（P<0.05）。经β多样性发现,曲皮和曲心样品间差异极显著（P<0.001）。属水平上,曲皮中的优势真菌属为复膜孢酵母属（Saccharomycopsis,98.92%）,而曲心中的优势真菌属为Saccharomycopsis（58.20%）和曲霉属（Aspergillus,40.97%）。在分类操作单元（operational taxonomic units,OTU）水平上,平均相对含量>1.0%的核心OTU仅2个,分别隶属于Saccharomycopsis（70.84%）和Aspergillus（17.91%）。经线性判别分析效应大小（linear discriminant analysis effect size,LEfSe）分析发现导致两者差异的主要菌群为Saccharomycopsis和Aspergillus等优势菌群。由此可见,后火低温大曲中主要的真菌类群为Saccharomycopsis和Aspergillus,且曲皮和曲心部位真菌群落结构存在差异,为后续制曲工艺的改良和华中地区酿酒微生物资源的挖掘提供一定的数据支撑。     

基于Illumina HiSeq技术分析浆水中细菌多样性及理化性质

基于Illumina HiSeq测序平台,对陕西、甘肃浆水中细菌16S rRNA基因V3～V4区进行测序,解析其细菌群落结构多样性。结果表明,各地浆水细菌菌群结构相似,多样性较高,其中,乳酸杆菌属丰度较高,占主导地位,发酵乳杆菌、乙醇片球菌和Lactobacillus parafarraginis为优势菌,相对丰度占比分别为33.39%、21.13%、3.28%。理化性质显示,浆水液盐度范围为0.09%～0.34%,pH值为3.32～4.00,酸度为0.194～0.872 g/L,亚硝酸盐含量为5.123～10.246 mg/kg,亚硝酸盐含量均低于我国酱腌菜卫生标准。浆水中乳酸含量最高,也含有甲酸、乙酸、丙酸、丁酸等多种短链脂肪酸,蔗糖、葡萄糖、果糖含量较少。本研究揭示陕西、甘肃不同地区浆水的细菌多样性及其理化性质,为传统发酵食品研究提供一定理论基础。     

甘南地区牦牛曲拉中细菌群落结构

基于Illumina MiSeq高通量测序平台,对甘南牦牛曲拉样品中细菌16S rRNA V3-V4区进行测序,通过α多样性、物种分类组成及β多样性分析对曲拉中细菌多样性及群落结构进行分析。结果表明：曲拉样品中优势门为厚壁菌门（Firmicutes）和变形菌门（Proteobacteria）,优势属为乳杆菌属（Lactobacillus）、醋酸杆菌属（Acetobacter）、乳球菌属（Lactococcus）,不同来源的样品中群落组成存在差异;细菌的功能基因预测表明,不同来源样品的细菌群落之间存在差异。研究结果可为曲拉的利用和食用安全性提供理论依据。     

致密储层同步压裂井间裂缝形态判别模型

在同步压裂过程中,随着地应力条件的改变,裂缝形态也会随之变化.针对这一现象,假设致密储层岩石为均质、各向同性材料,依据断裂力学理论,推导出同步压裂井间裂缝诱导应力计算模型;考虑水力压裂过程中,诱导应力差值对水平应力差异系数的影响,结合复杂裂缝和转向裂缝形成的力学条件,建立同步压裂井间裂缝形态判别模型.计算结果表明:压开裂缝附近水平应力差异系数场呈椭圆形分布,距离压开裂缝越近,水平应力差异系数越小,越易形成复杂或转向裂缝;初始地应力条件对同步压裂井间裂缝形态影响显著,文中压裂条件下,初始水平应力差异系数0＜Kho≤0.033时形成转向裂缝,0.033＜Kho＜0.361时形成复杂裂缝,Kho≥0.361时只能形成单一主裂缝.     

云计算时代的开放安全服务体系分析

针对移动互联网时代日益发展带来的安全性问题,在既要满足服务的多样性,又要满足服务安全性的双重使命下,如何构建移动互联网云计算时代开放安全的云服务,文中提出了一种开放的安全服务体系。同时,基于开发安全服务体系的各种技术特征,设计并构建了一个云服务平台架构,可以提供能力开放应用云、企业安全私有应用云和认证鉴权公共应用云。