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341.
Hersília de Andrade e Santos Paulo dos Santos Pompeu Danilo Okuma Lessa Kenji 《Regional Environmental Change》2012,12(1):123-132
Flow regulation causes various environmental impacts in the downstream reaches of impounded rivers. The S?o Francisco River
(SF) basin is Brazil’s third most important watershed. Several dams have been built in its course in the last four decades,
mostly for flow regulation and hydropower generation. This paper presents an evaluation of historical changes in the flood
regime. Three regions of the SF River basin, which are under the influence of different levels of regulation, were studied:
the lower, middle, and upper SF River. The components of magnitude, frequency, and duration of floods were quantified for
each region from 1940 to 1960 (prior to the construction of the first dam) and from 1986 to 2006 (after the last dam). The
results have shown the inexistence of big floods in the downstream areas, decreasing durations of small floods as well as
significant changes in the annual seasonality of floods. Reductions in the flood frequency were verified in all stretches,
even in non-regulated systems, such as the lower Velhas River. The climate variation, which occurred in both period, was not
able to explain the changes in the flood regime of S?o Francisco River; therefore, dams and other anthropogenic activity are
the main factors promoting the temporal variability of streamflows in the S?o Francisco basin. 相似文献
342.
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344.
Nonconsumptive predator effects are widespread and include plasticity as well as general stress responses. Caged predators are often used to estimate nonconsumptive effects, and numerous studies have focused on the larval stages of animals with complex life cycles. However, few of these studies test whether nonconsumptive predator effects, including stress responses, are exclusively sublethal. Nor have they assessed whether these effects extend beyond the larval stage, affecting success during stressful life-history transitions such as metamorphosis. We conducted experiments with larvae of a dragonfly (Leucorrhinia intacta) that exhibits predator-induced plasticity to assess whether the mere presence of predators affects larval survivorship, metamorphosis, and adult body size. Larvae exposed to caged predators with no ability to attack them had higher levels of mortality. In the second experiment, larvae reared with caged predators had higher rates of metamorphic failure, but there was no effect on adult body size. Our results suggest that stress responses induced by exposure to predator cues increase the vulnerability of prey to other mortality factors, and that mere exposure to predators can result in significant increases in mortality. 相似文献
345.
Populations of the Sydney rock oyster, Saccostrea glomerata, vary in response to ocean acidification
Acidifying oceans are predicted to fundamentally alter marine ecosystems. Over the next century, acute studies suggest that the impacts of climate change on marine organisms and ecosystems may be catastrophic. To date, however, little is known about whether the response of marine organisms varies within a species and whether this provides a potential ??adaptive capacity??. Here, we show that selectively bred lines of the ecologically and economically important estuarine mollusc, the Sydney rock oyster Saccostrea glomerata, are more resilient to ocean acidification than the wild populations. When reared at elevated pCO2, we found a 25% reduction in shell growth of the selectively bred population of the Sydney rock oyster, Saccostrea glomerata, compared to a 64% reduction in shell growth of wild populations. This study shows that there are significantly different sensitivities to ocean acidification even within the same species, providing preliminary evidence that selective breeding may be a solution for important aquaculture industries to overcome the future effects of ocean acidification. 相似文献
346.
Patricia Belinda Crosby Forbes Andreas Tr��e Egmont R. Rohwer 《Environmental Chemistry Letters》2011,9(1):7-12
Rapid methods are needed to analyse air pollutants such as polycyclic aromatic hydrocarbons (PAHs). Reliable semi-quantitative
gas standards were required for the development of a laser-induced fluorescence (LIF) method for polycyclic aromatic hydrocarbon
analysis, based on sampling of air onto multi-channel polydimethylsiloxane rubber traps. Easily constructed diffusion tubes
provided naphthalene vapour at ~2 ng s−1. A gas chromatographic fraction collection method for loading less volatile PAHs onto the traps from a flame ionization detector
outlet was developed and optimized. The accuracy of the method, which can be further optimized, was sufficient for initial
LIF screening tests to flag samples exceeding threshold PAH levels for subsequent quantitative GC–MS analysis. 相似文献
347.
J. A. Gonz��lez-P��rez F. J. Gonz��lez-Vila M. E. Arias J. Rodr��guez J. M. de la Rosa T. Mara?��n L. Clemente 《Environmental Chemistry Letters》2011,9(4):453-464
The bio-geographical significance of Rhododendron ponticum spp. baeticum (Ericaceae) as a relict species is well recognized. However, out of its native habitat it is an invasive exotic considered a major threat to natural ecosystems in areas of Atlantic Western Europe. The studies on the impact of Rhododendron influence on soil organic matter composition and associated ecological implications, i.e. presence of bioactive compounds with ecological significance, are limited. This work describes the soil lipid assemblage in three sites under Rhododendron stands and adjacent sites with deciduous oak (Quercus canariensis), both in their native habitats in Southern Spain (Sierra de Luna, Cádiz). The results are discussed in terms of organic matter dynamics and the presence of molecules that may be associated with Rhododendron invasive success. The soils are acid Xerochrepts formed on siliceous sands. Composite soil samples were taken at two depths (0?C10?cm and 10?C20?cm) and soxhlet extracted with a dichloromethane-methanol mixture (3:1). Soil lipid assemblage was studied by GC/MS after fractionation and appropriate derivatization of extracts. The qualitative chemical composition of soil extractable lipids under Rhododendron is reported here for the first time. Our results show that soil n-alkane and fatty acid distributions are compatible with an input from plant epicuticular waxes, as well as with the occurrence of selective preservation of long-chain fatty acids with depth. The pattern of short-chain n-alkanes found in surface samples indicates an anthropogenic contamination threat from nearby industrialized areas of ??Campo de Gibraltar??. The presence of branched iso and anteiso C15 and C17, ??-hydroxy fatty acids and the sterol brassicasterol points to high microbial soil activity. Finally, the pentacyclic triterpenes taraxerone and taraxerol were detected in soils with Rhododendron but not with Quercus. These are known bio-active plant compounds and could be related with the effectiveness of Rhododendron as an invasive exotic species. 相似文献
348.
P?emysl Sold��n 《Environmental monitoring and assessment》2011,178(1-4):349-359
Water ecosystems are threatened by accidental spills of pollution. Rapidity and trueness of information gathering the biological impact of accidental pollution is crucial for the efficiency of the minimisation of possible deterioration of ecosystems and for success in detecting the source of pollution. Due to the randomised occurrence of accidental spills the only way to quickly detect hazardous situations is to perform continuous monitoring of surface water quality. The current situation in the field of early warning in the International Odra (Oder) River basin is not satisfactory. The actual number of monitoring stations and list of routinely continuously monitored parameters are not able to meet the needs of sensitive and rapid detection of biological impact of accidental pollution spills. An effort to change this unfavourable situation was the reason for the offer survey, selection and a model operation of a commercially produced biological monitoring device. This apparatus was located on the border-line profile on the territory of the Czech Republic and represented the first and only one tool of continual biological monitoring of surface water quality in the International Odra (Oder) River Basin. The selected apparatus was the Daphnia Toximeter produced by the firm bbe Moldaenke (Kiel, Germany). This device exploited for rapid detection of changes of biological quality of surface water evaluation of behavioural response of monitoring organisms??daphnids. Five years of model operation proved its suitability for early warning purposes. The apparatus was reliable in function and sensitive enough to detect the deterioration of the biological quality of the river water. The given examples document its applicability not only for detection of accidental spills but also of illegal emissions of pollution, which are very often toxic. 相似文献
349.
Mayank Varun Rohan D��Souza Devendra Kumar Manoj S. Paul 《Environmental monitoring and assessment》2011,178(1-4):373-381
Toxicity of lead in soil is well documented and established. Phytoremediation has gained attention as a cheap, easily applicable, and eco-friendly clean-up technology. Chemical methods are used to assess exact levels and type of pollutants but heavy metal content in soil can also be evaluated indirectly by estimation of phytotoxicity levels using bioassays. Plant bioassays through fast germinating cereals can indicate not only the level of pollution and its effects on growth and survival but also the progress of phytoremediation process. The performance of barley Hordeum vulgare L. seedlings as bioassay for assessment of changes in the levels of lead (Pb) at three concentrations, i.e., 300 (T1), 600 (T2), and 1,200 ppm (T3) in the soil was evaluated while testing the efficiency of Crinum asiaticum L. as a phytoremedial tool. At the first assessment, i.e., 30 DAT (days after treatment) shoot and root lengths of seedlings decreased with increasing concentrations of Pb. As the study progressed, a decrease in levels of Pb was accompanied by better germinability and growth of barley. At 120 DAT seedling growth in all the treatments were comparable to control. In T1, T2, and T3 soils, 74.5%, 83.7%, and 91.2% reduction in lead content was observed at 120 DAT. Highly significant correlations between decreasing pollutant (Pb) content in the soil, seed germination, and seedling growth of barley H. vulgare were found. The differences in root and shoot length as well as overall growth pattern are indicative of the suitability of barley as a bio-monitoring tool. 相似文献
350.
Alberto Bouzas Daniel Aguado Nuria Mart�� Jos�� Manuel Pastor Rosa Herr��ez Pilar Campins Aurora Seco 《Environmental monitoring and assessment》2011,176(1-4):169-181
This paper reports the first results on alkylphenol pollution in edible bivalves from the Spanish coast. Two sampling campaigns (July 2006 and July 2007) were carried out to determine the concentration of nonylphenol (NP), octylphenol (OP), and eight polycyclic aromatic hydrocarbons (PAHs) in wild mussels (Mytilus galloprovincialys) and clams (Donax trunculus) at 14 sampling sites along the eastern Mediterranean Spanish coast. The results show that NP is the predominant alkylphenol, being the port of Valencia the most polluted area (up to 147 ??g/kg wet weight in clams). Moving away from the ports the concentration of NP in bivalves decreased. OP concentration was below its detection limit in most of the studied areas and its maximum concentration (6 ??g/kg w/w) was measured in clams from the port of Sagunto. The presence of low levels of PAHs was observed in most of the studied areas. The total PAHs concentration (i.e., sum of the eight measured PAHs) achieved a maximum value of 10.09 ??g/kg w/w in the north coast of Valencia city. The distribution pattern of the individual PAHs showed that both pollution sources petrogenic and pyrolytic were present in the sampled areas. Fluoranthene was the most abundant PAH in mussels while benzo(b)fluoranthene in clams. The maximum concentration of 10 ??g/kg w/w for benzo(a)pyrene established by the European Commission was never reached, indeed sampled bivalves showed concentrations 10 times lower than this reference value. Thus, they can be considered safe for human consumption. Despite the low contamination levels, the results show an overall pollution of bivalves by alkylphenol and PAHs as well as an increment in the number of polluted areas from 2006 to 2007. Thus, periodical sampling campaigns should be carried out to monitor the long-term tendency of these toxic and persistent pollutants. 相似文献