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1.
1. We set out to evaluate the reliability of bacterial communities as an indicator of freshwater ecological health.
2. Samples of epilithic biofilm were taken over a 1-year period from four streams, each impacted by varying degrees of human modification. The bacteria within each sample were characterised using a whole community DNA fingerprinting technique (automated ribosomal intergenic spacer analysis). Spatial and temporal differences in community structure between samples were visualised using multi-dimensional scaling and quantified using permutational multivariate anova . Macrobenthic invertebrates, which are commonly used as indicators of stream ecological health, were also sampled for comparison.
3. Multivariate analysis revealed a clear gradient in macroinvertebrate community structure between sites exposed to increased human impact. Bacterial communities, however, could only distinguish the most impacted site from the remainder.
4. Additional research is required to increase the sensitivity of bacterial community analyses before endorsing their use as an indicator of freshwater ecological health.  相似文献   

2.
1. This study summarises our development and application in developing countries of a process for assessing the ecological, social and economic costs and benefits of water-resource developments, as an aid to basin planning.
2. During 15 years of work in Africa and Asia, the process sequentially included the whole river ecosystem and the whole flow regime in the assessment; used a multidisciplinary team and a scenario-based approach that gave equal weighting to the ecological, social, resource-economic and macro-economic costs and benefits of development; quantified or semi-quantified the costs and benefits in data-poor situations, capturing expert opinion and local wisdom as well as data; recognised that the final allocation of water for ecosystem maintenance should be a societal choice of trade-offs between resource protection and development.
3. Flow assessments were increasingly done at the basin rather than project level and introduced the concept and practicality of Development Space as a tool to aid basin planning.
4. Later assessments included valuation of regulating, cultural and provisioning services provided by rivers as part of the cost-benefit analysis.
5. Implementation of managed flows as outlined above is a complex and long-term process that should include a number of major steps, from development of the appropriate legislation to monitoring of management decisions and adaptive management. Country or region-wide implementation at this scale could well take one to two decades, even where the political will and technical skills exist.
6. We conclude by offering eight principles that we believe would promote genuinely sustainable use of rivers.  相似文献   

3.
SUMMARY 1. In Europe, water policy is currently undergoing considerable change as emphasised by the recent European Water Framework Directive (WFD), which requires the restoration and maintenance of 'healthy' aquatic ecosystems by the assessment of their hydromorphological, chemical and biological characteristics. If the requirements of the WFD are to be met, effective biological tools are needed to measure the 'health' of rivers at scales large enough to be useful for management. These tools need to be ecologically based, efficient, rapid and applicable in different ecological regions. Among potential indicators, fish assemblages are of particular interest because of their ability to integrate environmental variability at different spatial scales. To meet the goals of the WFD, the French Water Agencies and the Ministry of the Environment initiated a research programme to develop a fish-based index that would be applicable nationwide.
2. A variety of metrics based on occurrence and abundance data and reflecting different aspects of the fish assemblage structure and function were selected from available literature and for their potential to indicate degradation.
3. Logistic and multiple linear regression procedures were applied, using an initial data set of 650 reference sites fairly evenly distributed across French rivers and defined by some easily measured regional and local characteristics, to elaborate the simplest possible response model that adequately explained the observed patterns of each metric for a given site.
4. Models obtained for each metric were validated using two independent data sets of 88 reference sites and 88 disturbed sites. These procedures allowed us to select the most effective metrics in discriminating between reference and disturbed sites.  相似文献   

4.
1.  Describing distribution and abundance is requisite to exploring interactions between organisms and their environment. Recently, the resource selection function (RSF) has emerged to replace many of the statistical procedures used to quantify resource selection by animals.
2.  A RSF is defined by characteristics measured on resource units such that its value for a unit is proportional to the probability of that unit being used by an organism. It is solved using a variety of techniques, particularly the binomial generalized linear model.
3.  Observing dynamics in a RSF – obtaining substantially different functions at different times or places for the same species – alerts us to the varying ecological processes that underlie resource selection.
4.  We believe that there is a need for us to reacquaint ourselves with ecological theory when interpreting RSF models. We outline a suite of factors likely to govern ecologically based variation in a RSF. In particular, we draw attention to competition and density-dependent habitat selection, the role of predation, longitudinal changes in resource availability and functional responses in resource use.
5.  How best to incorporate governing factors in a RSF is currently in a state of development; however, we see promise in the inclusion of random as well as fixed effects in resource selection models, and matched case–control logistic regression.
6.  Investigating the basis of ecological dynamics in a RSF will allow us to develop more robust models when applied to forecasting the spatial distribution of animals. It may also further our understanding of the relative importance of ecological interactions on the distribution and abundance of species.  相似文献   

5.
Aim   To contribute to the development of a macroevolutionary framework for riparian systems, reinforcing conceptual linkages between earth surface processes and biological and ecological processes.
Location   Riparian systems.
Methods   Literature review leading to an original proposition for perceiving the functioning of riparian systems in a new and different way.
Results   Riparian systems provide diverse landforms, habitats and resources for animals and plants. Certain organisms, defined as 'ecosystem engineers', significantly create and modify the physical components of riparian systems. Many studies have highlighted such engineering effects by animals on riparian systems, but the identification and understanding of the effects and responses of plants within fluvial corridors have emerged only recently. The modulation of matter, resources and energy flows by engineering plants helps establish characteristic sequences of fluvial landform creation and maintenance associated with synergetic ecological successions. We relate this process to the concept of niche construction, developed mainly by evolutionary biologists. Feedbacks between adaptive responses of riparian plants to flow regime and adjusting effects on biostabilization and bioconstruction are discussed in the context of niche construction at the scale of ecological succession and the evolution of organisms.
Main conclusions   Our conceptualization forges an integrated approach for understanding vegetated fluvial systems from a macroevolutionary perspective, for elucidating riparian ecosystem dynamics and potentially for establishing long-term stream conservation and restoration strategies.  相似文献   

6.
1. The European Water Framework Directive provides a framework for improving the ecological quality of stream ecosystems, with deviation from reference used as a measure of ecological status.
2. Here we examine the possibility of using less impacted stream sites from Latvia, Lithuania and Poland to establish a Danish reference network for macrophyte assemblages, and as a guiding image for identification of possible references sites within Denmark. Both approaches were evaluated using historical Danish records.
3. Four different macrophyte assemblages were identified for mid-sized streams in the Central and Eastern Lowland ecoregions. Macrophyte assemblages could not be delineated using physical stream site characteristics; however a gradual change in assemblage composition was attributed to differences in alkalinity and human impact.
4. Assemblages of contemporary vegetation in Denmark were quite similar to those found in Polish, Latvian and Lithuanian streams (26–35%). However, more importantly, from species-based predictions we noted higher similarity, particularly with Latvian and Lithuanian streams, before intensive land use commenced in Denmark ( c. 1900). These results show that stream sites from these three countries can be considered in a Danish reference network.
5. Two of the four macrophyte assemblages comprised species such as Fontinalis antipyretica, Myriophyllum spicatum , Nuphar lutea , Potamogeton alpinus and P. perfoliatus that have a very scattered occurrence in the contemporary vegetation in Denmark. These groups were closely associated with the predictions from historic records, thereby lending support the conjecture that these assemblages could be part of the guiding image for the identification of potential reference sites within Denmark.  相似文献   

7.
1. Estimates of the Lyapunov exponent, a statistic that measures the sensitive dependence of the dynamic behaviour of a system on its initial conditions, are used to characterize several sets of insect time series.
2. A new method is described to overcome the difficulty of defining the dynamics of an observed, noisy, short ecological time series. This method provides two test statistics for the estimated Lyapunov exponent.
3. This method is applied to forty-six time series comprising six aphid species from five sites and four moth species from six sites. There are few positive Lyapunov exponents and none is sufficiently large to characterize its time series as chaotic.
4. Two methods to estimate the Lyapunov exponent are compared; that based on logarithmically transformed counts yields less variable estimates for highly variable insect data than that based on untransformed counts.  相似文献   

8.
Increasing anthropogenic impacts on biodiversity has been a cause for concern in Australia in recent years. Areas that hold high levels of endemic species and also face exceptional threats of destruction have been described as biodiversity hotspots. Ecological research focused on biodiversity hotspots will provide a better understanding of the flora and fauna of these regions and thus inform conservation strategies. Consequently, it is important to understand where biodiversity hotspots are located and how well they have been researched in the past. However, the choice of ecological research sites may be influenced by a variety of factors such as proximity to research institutions. This study utilized a geographic information system to investigate the spatial distribution of ecological research field sites in Australia and its territorial waters, the hotspots of the field sites around research institutions and the proximity of ecological research field sites from the main campus of the research institutions. Furthermore, these hotspots of ecological research were linked to biodiversity hotspots to identify the regions that were commonly depicted in the ecological literature and to identify others that may need more attention. We demonstrated that hotspots of ecological research were concentrated around research institutions, with a large number of field sites being located between 0 km and 500 km from the nearest institution, especially along the eastern coast. This study highlighted areas that have been the focus of much ecological research as well as areas that need more attention from ecologists to add new knowledge to Australian ecological science.  相似文献   

9.
Aims:  The aim of this study is to isolate and characterize organisms capable of utilizing high concentration atrazine from the contaminated sites.
Methods and Results:  A selective enrichment was used for isolating atrazine-degrading organisms from the contaminated sites resulting in isolation of an efficient atrazine-degrading organism designated as strain MB-P1. On the basis of 16S rRNA gene sequencing, total cellular fatty acid analysis and physiological and biochemical tests, strain MB-P1 was identified as a member of genus Rhodococcus . High performance liquid chromatography was performed to identify the atrazine degradation intermediates demonstrating that the degradation proceeds via formation of 'de-ethylatrazine' and 'de-isopropylatrazine'. Further, plasmid curing by SDS method showed atrazine-degrading gene(s) to be plasmid-encoded.
Conclusions:  We have successfully isolated a Rhodococcus sp. strain MB-P1 which is capable of utilizing atrazine as sole source of carbon and energy at very high concentrations of 1000 ppm. The pathway for degradation of atrazine has also been determined. The metabolic gene(s) responsible for atrazine degradation was found to be plasmid-encoded.
Significance and Impact of the Study:  Rhodococcus sp. strain MB-P1 could be used as an ideal model system for in-situ degradation and restoration of ecological niches which are heavily contaminated with atrazine.  相似文献   

10.
Aim  Lepidium latifolium (Brassicaceae; perennial pepperweed) is a noxious Eurasian weed invading riparian and wetland areas of the western USA. Understanding which sites are most susceptible to invasion by L. latifolium will allow more efficient management of this weed. We assessed the ability of advanced remote sensing techniques to develop habitat suitability models for L. latifolium .
Location  San Francisco Bay/Sacramento-San Joaquin River Delta, California, USA.
Methods  Lepidium latifolium distribution was mapped with hyperspectral image data of Rush Ranch Open Space Preserve, providing presence/absence data to train and validate habitat models. A high-resolution light detection and ranging digital elevation model was used to derive predictor environmental variables (distance to channel, distance to upland, elevation, slope, aspect and convexity). Aggregate decision tree models were used to predict the potential distribution of this species.
Results  Lepidium latifolium infested two zones: near the marshland–upland margin and along channels within the marsh. Topographical data, which are typically strongly correlated with wetland species distributions, were relatively unimportant to L. latifolium occurrence, although relevant microtopography information, particularly relative elevation, was subsumed in the distance to channel variable. The map of potential L. latifolium distribution reveals that Rush Ranch contains considerable habitat that it is susceptible to continued invasion.
Main conclusions  Lepidium latifolium invades relatively less stressful sites along the inundation and salinity gradients. Advanced remote sensing datasets were shown to be sufficient for species distribution modelling. Remote sensing offers powerful tools that deserve wider use in ecological research and management.  相似文献   

11.
Diatoms as indicators of water quality in some English urban lakes   总被引:1,自引:0,他引:1  
SUMMARY. 1. The paper describes diatom communities from a series of linked urban lakes in relation to water chemistry and uses multivariate statistical techniques to show how indicator groups can he defined.
2. Diatoms are classified into ecological groups using two-way species indicator analysis (TWINSPAN). Each ecological group is associated with a specific range of water-quality conditions. The headwater stream environments are differentiated from the lake habitats at level 1. At level 2 of TWINSPAN. the sampling sites are grouped into five ecological groups, according to their water chemistry and irrespective of the time of year.
3. Detrended correspondence analysis (DCA) and principal components analysis (PCA) provide two statistically independent methods of assessing the environmental gradients along which the ecological groups are distributed. The most important physico-chemical parameters are total hardness, specific conductance and pH, followed by phosphates and nitrates.
4. Ecological groups I-V correspond to an environmental gradient ranging from the forested headwaters, which are acidic, of low specific conductance, total hardness and nutrient content, through the urban lakes, which are alkaline and of relatively high total hardness, specific conductance and nutrient content.
5. Twelve site groups are identified at level 3 of TWINSPAN, each of which corresponds to a narrower range of water-quality conditions within the ecological groupings. A specific diatom assemblage is associated with each site group.
6. Benthic diatoms form an integral part of the diatom assemblages found in the water column and this is identified as a topic for further study.  相似文献   

12.
1. At two organically polluted sites in the River Nethravathi, banyan and eucalypt leaves were colonized by one or two species of aquatic hyphomycetes. A total of three or four species were identified at the two sites in samples of water and naturally occurring leaves.
2. Spore production from stream‐exposed leaves by aquatic hyphomycetes was lower by a factor of up to 1 million compared with an earlier study in geographically close but unpolluted streams.
3. Exponential decay rates and loss rates of phosphorus and calcium, were not statistically different from an earlier study in unpolluted streams. Nitrogen increased during decomposition more slowly in the current study.
4. The microbial community on both leaves released enzymes active against starch, pectin, cellulose and xylan.
5. Banyan leaves conditioned for 12 weeks were more palatable to the gastropod Notopala sp. than unconditioned leaves.
6. Together with earlier data from unpolluted streams, the study provides evidence that organic pollution severely restricts diversity of aquatic hyphomycetes and their reproductive output, but does not have an equally strong effect on ecological functions generally associated with this group.  相似文献   

13.
Ntiamoa-Baidu, Y. & Gordon, C. 2000. Waterbird & wetland research and conservationin Ghana: a ten year perspective. Ostrich 71 (1 & 2): 95.

The study outlines the evolution of ecological research on waterbirds and wetland conservation initiatives in Ghana over a ten year period, 1986–1996. A survey of waterbird populations was initiated in the country in October 1985, through a collaborative effort between the Ghana Government, the Royal Society for the Protection of Birds (RSPB) UK and BirdLife International. These studies identified key wetland sites on the Ghana coast which have been regularly monitored up to today, thus providing the most comprehensive long-term data on waterbird populations within the West African sub-region. Over the ten year period the simple waterbird counting has led to comprehensive ecological research on waterbirds, the establishment of a national Bird Ringing Scheme and the development of a core of trained ornithologists in Ghana. In terms of conservation action, the data provided the justification for designation of the five most important coastal wetland sites as Ramsar sites and the establishment of the Ghana Coastal Wetlands Management Project (CWMP) to manage the sites. The management strategy adopted seeks not only to maintain the ecological integrity of the wetlands, but more importantly, to enhance the benefits derived from wetlands by local communities and improve the quality of life for the coastal people. Management actions are guided by a multi-disciplinary research on the coastal wetland ecosystem, which incorporates biological, physico-chemical and socio-economic dimensions. The large body of environmental data accumulated during the initial stages of the CWMP provide a solid base for the monitoring of the ecological character of the wetlands and the evaluation of management activities. The events in Ghana clearly demonstrate the value of a strong scientific data-base in our efforts to promote conservation of Africa's wetlands and wetland resources.  相似文献   

14.
SUMMARY. 1. Changes in species composition of the periphyton on introduced substrates were determined in an oligotrophic mountain stream subject to long-term heavy metal contamination.
2. At the upstream control site, the numerically most abundant taxa were Bacillarioph yta i( Achnanlhes minutissima, Achnanthes microcephala and Achnanthes linearis ) as well as, in summer, the Chlorophyta ( Mougeotia spp. and Ulothrix subtilissima ).
3. At the downstream contaminated site the periphyton community was totally dominated by Bacillariophyta throughout the sampling period. A, minutissima and A, microcephala were co-dominants during spring. Seasonal succession patterns did not parallel those at the upstream site. Chlorophyta were virtually absent and A. minutissima comprised 94% of the community during summer.
4. Species diversity, species evenness and dissimilarity index were utilized to detect differences in species composition, abundance and number. Slight differences were found in spring samples while summer samples indicated major differences between sampling sites.  相似文献   

15.
1. The diatom Didymosphenia geminata has emerged in recent years as a globally invasive species. Although considered native to North America, reports of nuisance blooms have increased over the last decade.
2. Previously, we determined that D. geminata was ubiquitous in two major headwaters of the South Saskatchewan River Basin (SSRB), Alberta, Canada, but found it only bloomed at certain sites, including those immediately downstream from dam outfalls. To evaluate the role of dams in the abundance and blooming of D. geminata , we compared sites just below dams to unregulated upstream reference sites in six dammed rivers of the SSRB.
3. There was a high degree of seasonal variability in D. geminata abundance among sites, but statistical analyses showed a significant propensity for the diatom to have higher cell densities and an increased frequency of blooms at dam sites.
4. Important predictor variables of D. geminata abundance included dam presence, water clarity and total phosphorus concentration. When data from dam sites were analysed, a multiple regression model using mean discharge and pH as independent predictors explained 73% of the variation in D. geminata cell density.
5. Analysis of 3 years of data from one study river (Red Deer River) revealed consistently higher D. geminata cell densities at the dam site compared to the upstream reference. This analysis also showed that average cell density fluctuated by orders of magnitude from year-to-year.
6. Due to the ecological and aesthetic concerns regarding the global spread and blooming of D. geminata , we recommend that dams be viewed as key candidates for mitigating blooms in flow regulated systems.  相似文献   

16.
1.  The evaluation of restoration measures is an important task of conservation biology. Inland sand dunes and dry, oligotrophic grasslands have become rare habitat types in large parts of Central Europe and their restoration and management is of major importance for the preservation of many endangered plant and insect species. Within such habitats, it is important to restore key ecosystem services, such as pollination networks. As wild bees are the most important pollinators in many ecosystems, they represent a suitable key group to evaluate restoration measures. Furthermore, the recent decline of many bee species and the potential ecological and economic consequences are currently topics of strong scientific interest.
2.  We studied the succession of bee communities in response to restoration measures of sand dunes and sand grasslands and compared these communities with those of old sand dune complexes.
3.  Our results show that wild bees respond rapidly to restoration measures indicated by a high species richness and abundance. The community structure of bees at restoration sites converged only slightly to those of the target sites. A higher similarity was found between bee communities at the restoration sites (sand dunes and grasslands), indicating that their close proximity was an important determinant of species overlap. Environmental factors such as the number of entomophilous plant species and moisture had a strong influence on wild bee species composition.
4.   Synthesis and applications . The restoration of inland sand dune complexes provides opportunities for colonization by a diverse wild bee community. Although it is difficult to establish a given target community, restoration measures gave rise to a high pollinator diversity and abundance, suggesting that community function can be re-established.  相似文献   

17.
SUMMARY 1. A challenge has been issued to ecologists to find quantitative ecological relationships that have predictive power. A predictive approach has been successful when applied to biomonitoring using stream invertebrates with the River Invertebrate Prediction and Classification System (RIVPACS). This approach, to our knowledge, has not been applied to freshwater fish assemblages.
2. This paper describes the initial results of the application of a regional predictive model of freshwater fish occurrence using 200 reference sites sampled in the Manawatu–Wanganui region of New Zealand over late summer/autumn 2000. In brief (i) sites were classified into biotic groups (ii) the physical and chemical characteristics that best describe variation among these groups were determined and (iii) the relationship between these environmental variables and fish communities was used to predict the fauna expected at a site.
3. Reference sites clustered into six groups based on fish density and community composition. Using 14 physical variables least influenced by human activities, a discriminant model allocated 70% of sites to the correct biological classification group. The variables that best separated the site groups were mainly large-scale variables including altitude, distance from the coast, lotic ecoregion and map co-ordinates.
4. The model was further validated by randomly removing 20% of the sites, rebuilding the model and then determining the number of removed sites correctly allocated to their original biotic groups using environmental variables. Using this process 67% of the removed sites were correctly reassigned to the six predetermined groups.
5. A further 30 sites were used to determine the ability of the model to detect anthropogenic impact. The observed over expected taxa ( O / E ) ratios were significantly lower than the reference site O / E ratios, indicating a response of the fish assemblages to the known stressors.  相似文献   

18.
Natura 2000 sites are expected to assure the long-term survival of Europe’s most valuable and threatened species and habitats. It follows that successful management of the sites is of great importance. Next to goal attainment, cost-effectiveness is increasingly recognised as a key requirement for gaining social and political acceptance for costly conservation measures. We identify and qualitatively examine issues of cost-effectiveness related to the design and implementation of management measures in Natura 2000 sites in Finland, Germany, the Netherlands and Poland. Given the wide variety of management design and implementation options within the four countries, our study is purely of an exploratory nature. We derive recommendations for improving the cost-effectiveness of management in Natura 2000 sites and for future research. Examples of policy recommendations include guaranteeing the availability of funds for longer periods, and ensuring the appropriate allocation of funds between the different tasks of designing and implementing management plans. Further research should examine the cost-effectiveness of controversial suggestions such as, for example, more tailored payment schemes for conservation measures that result in higher ecological outputs but are costly to administer. Moreover, more research is needed to better understand how rules for administrations, as well as rules and governance structures for tasks within administrations, should be designed.  相似文献   

19.
1. The patterns of arthropod diversity were investigated in 24 montane wetlands in Switzerland. These differed in altitude, management regime (cattle-grazing vs. mowing), vegetation structure (index combining vegetation height and density) and degree of habitat fragmentation.
2. The general arthropod diversity was determined by net sampling at 10 sampling points per site. The diversity of grasshoppers and butterflies was measured by counting species richness at the site and species density (species richness per unit area) on transects. The species richness of grasshoppers and butterflies was found to be more sensitive to the geographical attributes of the site whereas species density was more affected by the habitat quality.
3. Grasshopper diversity decreased within the observed altitudinal range (800–1400 m) and was higher at grazed sites, whereas butterfly diversity was higher at mown sites. Arthropod diversity but not abundance of arthropods was positively related to the vegetation structure.
4. The species richness of butterflies was negatively influenced by the degree of habitat fragmentation: both the size of habitat as well as the area of wetland habitats within 4 km were related positively to the number of specialist wetland butterflies.
5. Late mowing as well as low-density cattle-grazing are appropriate management actions to maintain arthropod diversity in montane wetlands. In order to establish site-specific management plans, the biology of the present target species as well as the historical context should be considered.
6. We suggest that the best protection for the species examined in this study would be a network of wetland sites managed using a variety of traditional, non-intensive methods. This can only be achieved by coordinated planning of conservation measures among sites.  相似文献   

20.
Aim  To generate maps of potential refugia for summer-green trees during the Last Glacial Maximum (LGM).
Locations  Southern Europe and south-western Asia.
Methods  Time-slice simulations of the atmospheric climate with the ECHAM3 model are used for the LGM. Limiting factors beyond which cool and warm groups of deciduous trees cannot grow (such as temperature in growing degree days, minimum monthly temperature and precipitation in summer) are chosen. A limited validation by fossil pollen and charcoal records from LGM sites was done.
Results  Two sets of maps extending from Europe to the Caspian region for cool and warm summer-green trees are presented. Three criteria are combined using contour lines to indicate confidence levels. Small areas within the three southern peninsulas of Europe (Spain, Italy and Greece) are highlighted as possible refugia for summer-green trees. Further, areas that have remained poorly known are now proposed as refugia, including the Sakarya–Kerempe region in northern Turkey, the east coast of the Black Sea and the area south of the Caspian Sea.
Main conclusions  The maps produced in this study could be used to facilitate better long-term management for the protection of European and south-western Asian biodiversity.  相似文献   

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