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211.
Joseph B Yamakanamardi SM 《Journal of environmental biology / Academy of Environmental Biology, India》2011,32(5):551-557
Zooplankton abundance and distribution are of ecological importance, as they are very sensitive to change, therefore zooplankton make ideal indicators of aquatic ecosystem. This study carried out on the abundance of rotifer, cladoceran, cyclopoid-copepod and ostracod zooplankton groups and biomass of total zooplankton were studied every month for one year. It is interesting and noteworthy to note that Calanoid and Harpacticoid zooplankton groups and free carbon dioxide were completely absent in all the four sampling sites throughout the study year. About 53% of the variation in the abundance of Cladoceran, 55% of variation in the Cyclopoid-copepod, 39% of variation in the ostracod and 53% of variation in the abundance of total zooplankton were mainly due to pH. Interestingly, negative relationship was found between the total zooplankton and concentration of phosphate as in this lake 67% decrease in wet biomass was mainly because of phosphate, where as 47% of dry biomass of total zooplankton was positively correlated with conductivity. 相似文献
212.
Understanding the ecology of extinction is one of the primary challenges facing ecologists in the 21st century. Much of our current understanding of extinction, particularly for invertebrates, comes from studies with large geographic coverage but less temporal resolution, such as comparisons between historical collection records and contemporary surveys for geographic regions or political entities. We present a complementary approach involving a data set that is geographically restricted but temporally intensive: we focus on three sites in the Central Valley of California, and utilize 35 years of biweekly (every two weeks) surveys at our most long-sampled site. Previous analyses of these data revealed declines in richness over recent decades. Here, we take a more detailed approach to investigate the mode of decline for this fauna. We ask if all species are in decline, or only a subset. We also investigate traits commonly found to be predictors of extinction risk in other studies, such as body size, diet breadth, habitat association, and geographic range. We find that population declines are ubiquitous: the majority of species at our three focal sites (but not at a nearby site at higher elevation) are characterized by reductions in the fraction of days that they are observed per year. These declines are not readily predicted by ecological traits, with the possible exception of ruderal/non-ruderal status. Ruderal species, in slightly less precipitous decline than non-ruderal taxa, are more dispersive and more likely to be associated with disturbed habitats and exotic hosts. We conclude that population declines and extirpation, particularly in regions severely and recently impacted by anthropogenic alteration, might not be as predictable as has been suggested by other studies on the ecology of extinction. 相似文献
213.
Schloderer G Bingham M Awange JL Fleming KM 《Environmental monitoring and assessment》2011,180(1-4):147-161
In environmental monitoring, environmental impact assessments and environmental audits, topographical maps play an essential role in providing a means by which the locations of sampling sites may be selected, in assisting with the interpretation of physical features, and in indicating the impact or potential impact on an area due to changes in the system being monitored (e.g., spatially changing features such as wetlands). Global Navigation Satellite Systems (GNSS) are hereby presented as a rapid method for monitoring spatial changes to support environmental monitoring decisions and policies. To validate the GNSS-based method, a comparison is made of results from a small-scale topographic survey using radio-based real-time kinematic GNSS (GNSS-RTK) and total station survey methods at Jack Finnery Lake, Perth, Australia. The accuracies achieved by the total station in this study were 2 cm horizontally and 6 cm vertically, while the GNSS-RTK also achieved an accuracy of 2 cm horizontally, but only 28 cm vertically. While the GNSS-RTK measurements were less accurate in the height component compared to those from the total station method, it is still capable of achieving accuracies sufficient for a topographic map at a scale of 1:1,750 that could support environmental monitoring tasks such as identifying spatial changes in small water bodies or wetlands. The time taken to perform the survey using GNSS-RTK, however, was much shorter compared to the total station method, thereby making it quite suitable for monitoring spatial changes within an environmental context, e.g., dynamic mining activities that require rapid surveys and the updating of the monitored data at regular intervals. 相似文献
214.
Omo O. Omo-Irabor Samuel B. Olobaniyi Joe Akunna Valentijn Venus Joseph M. Maina Charles Paradzayi 《Environmental monitoring and assessment》2011,178(1-4):39-51
Mangroves are known for their global environmental and socioeconomic value. Despite their importance, mangrove like other ecosystems is now being threatened by natural and human-induced processes that damage them at alarming rates, thereby diminishing the limited number of existing mangrove vegetation. The development of a spatial vulnerability assessment model that takes into consideration environmental and socioeconomic criteria, in spatial and non-spatial formats has been attempted in this study. According to the model, 11 different input parameters are required in modelling mangrove vulnerability. These parameters and their effects on mangrove vulnerability were selected and weighted by experts in the related fields. Criteria identification and selection were mainly based on effects of environmental and socioeconomic changes associated with mangrove survival. The results obtained revealed the dominance of socioeconomic criteria such as population pressure and deforestation, with high vulnerability index of 0.75. The environmental criteria was broadly dispersed in the study area and represents vulnerability indices ranging from 0.00?C0.75. This category reflects the greater influence of pollutant input from oil wells and pipelines and minimal contribution from climatic factors. This project has integrated spatial management framework for mangrove vulnerability assessment that utilises information technology in conjunction with expert knowledge and multi-criteria analysis to aid planners and policy/ decision makers in the protection of this very fragile ecosystem. 相似文献
215.
采用简单的原位沉淀法合成了可见光驱动型光催化剂Ag3PO4/g-C3N4.利用X-射线衍射(XRD)、傅里叶红外光谱(FT-IR)、扫描电子显微镜(SEM)、X-射线能谱(XPS)以及紫外可见漫反射光谱(UV-Vis DRS)等表征手段对合成的样品进行了表征.与单一的Ag3PO4和g-C3N4相比,Ag3PO4/g-C3N4复合材料对左氧氟沙星表现出了更高的催化效率.根据能带分析和自由基捕获试验,提出了Ag3PO4/g-C3N4复合材料Z型异质结构的作用机制. 相似文献
216.
Although biological invasions are of considerable concern to ecologists, relatively little attention has been paid to the potential for and consequences of indirect interactions between invasive species. Such interactions are generally thought to enhance invasives' spread and impact (i.e., the "invasional meltdown" hypothesis); however, exotic species might also act indirectly to slow the spread or blunt the impact of other invasives. On the east coast of the United States, the invasive hemlock woolly adelgid (Adelges tsugae, HWA) and elongate hemlock scale (Fiorinia externa, EHS) both feed on eastern hemlock (Tsuga canadensis). Of the two insects, HWA is considered far more damaging and disproportionately responsible for hemlock mortality. We describe research assessing the interaction between HWA and EHS, and the consequences of this interaction for eastern hemlock. We conducted an experiment in which uninfested hemlock branches were experimentally infested with herbivores in a 2 x 2 factorial design (either, both, or neither herbivore species). Over the 2.5-year course of the experiment, each herbivore's density was approximately 30% lower in mixed- vs. single-species treatments. Intriguingly, however, interspecific competition weakened rather than enhanced plant damage: growth was lower in the HWA-only treatment than in the HWA + EHS, EHS-only, or control treatments. Our results suggest that, for HWA-infested hemlocks, the benefit of co-occurring EHS infestations (reduced HWA density) may outweigh the cost (increased resource depletion). 相似文献
217.
We conducted two ship-based surveys of the nearshore ecosystem north of Livingston Island, Antarctica during 2–10 February
2005. Between the two surveys, a low-pressure system (963 mbar) passed through the area providing the opportunity to measure
ecosystem parameters before and after a near gale. A ship-based multiple-frequency acoustic-backscatter survey was used to
assess the distribution and relative abundance of Antarctic krill (Euphausia superba). Net tows, hydrographic profiles, and meteorological data were collected to measure biological and physical processes that
might affect the krill population. During the survey, the distribution and behavior of several krill predators [chinstrap
penguins (Pygoscelis antarctica), cape petrels (Daption capense), and Antarctic fur seals (Arctocephalus gazella)] were measured from the vessel by visual observations. The survey encompassed an area of roughly 2,500 km2, containing two submarine canyons with one to the west and one to the east of Cape Shirreff, which had different abundances
of krill and predators. Several aspects of the nearshore ecosystem changed after the near gale including: hydrography of the
upper 100 m of the water column, phytoplankton biomass, the abundance and distribution of krill, and the distribution of some
krill predators. Differences in these parameters were also measured between the two canyons. These changes in the physical
and biological environment during the survey period are quantified and show that the ecosystem exhibited significant changes
over relatively short spatial (tens of kilometers) and time (tens of hours) scales. 相似文献
218.
Gorsevski PV Donevska KR Mitrovski CD Frizado JP 《Waste management (New York, N.Y.)》2012,32(2):287-296
This paper presents a GIS-based multi-criteria decision analysis approach for evaluating the suitability for landfill site selection in the Polog Region, Macedonia. The multi-criteria decision framework considers environmental and economic factors which are standardized by fuzzy membership functions and combined by integration of analytical hierarchy process (AHP) and ordered weighted average (OWA) techniques. The AHP is used for the elicitation of attribute weights while the OWA operator function is used to generate a wide range of decision alternatives for addressing uncertainty associated with interaction between multiple criteria. The usefulness of the approach is illustrated by different OWA scenarios that report landfill suitability on a scale between 0 and 1. The OWA scenarios are intended to quantify the level of risk taking (i.e., optimistic, pessimistic, and neutral) and to facilitate a better understanding of patterns that emerge from decision alternatives involved in the decision making process. 相似文献
219.
Multilevel marketing organizations (MLMs) are a rapidly growing organizational type enlisting nearly 10 million members and producing over 20 billion dollars in sales annually. Despite their remarkable recent growth, few studies have examined these unusual organizations, and none of these have addressed issues of transformational leadership. In MLMs, the key leadership relationships are those between individual member distributors and the members who recruited them into the organization (i.e., their ‘sponsors’). Although sponsors are expected to provide leadership to the members they recruit, they possess no direct supervisory resulting—authority in an uncertain ‘quasi‐leadership’ role. Using a sample of 736 female MLM members, the present study empirically tests an important explanatory component of transformational leadership theory: that belief in the higher purpose of one's work is a mechanism through which transformational leadership achieves its positive outcomes on cohesion, satisfaction, effort, and performance. The results offer support to the notion that transformational leadership indeed ‘transforms’ followers by encouraging them to see the higher purposes in their work. Additionally, the results show positive relationships between belief in a higher purpose of one's work and job satisfaction, unit cohesion, and effort. Copyright © 2001 John Wiley & Sons, Ltd. 相似文献
220.
Joseph S. Stibrich Thomas J. Charles 《Journal of the American Water Resources Association》2000,36(6):1263-1269
ABSTRACT: This paper describes how a hydrologic model proved to be a valuable tool to help interested parties understand impacts to four threatened and endangered fish species in the Upper Colorado River. In 1994, the Ute Water Conservancy District initiated permitting and design of the Plateau Creek pipeline replacement. The project was considered a major Federal action and therefore subject to the National Environmental Policy Act. Under Section 7 of the Endangered Species Act, the U.S. Fish and Wildlife Service (USFWS) entered the process to develop a Biological Opinion (BO) and determined that the project could potentially impact the endangered fish in the 15‐mile reach of the Colorado River. The Section 7 consultation was directed by a Core Committee comprised of stakeholders in the Upper Colorado River watershed. Hydrologic modeling became the evaluation tool for comparing flow reductions to USFWS target recovery flows and defining make‐up flow requirements to meet those targets. The Colorado River Recovery Implementation Program was designated to provide the make‐up flows. The USFWS released a final BO in December 1997, approving diversions through 2015. An Environmental Impact Statement for the project was completed and the Record of Decision was issued by the Bureau of Land Management in early 1998. 相似文献