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231.
Environmental variability, costs of reproduction, and heterogeneity in individual quality are three important sources of the temporal and interindividual variations in vital rates of wild populations. Based on an 18-year monitoring of an endangered, recently described, long-lived seabird, Monteiro's Storm-Petrel (Oceanodroma monteiroi), we designed multistate survival models to separate the effects of the reproductive cost (breeders vs. nonbreeders) and individual quality (successful vs. unsuccessful breeders) in relation to temporally variable demographic and oceanographic properties. The analysis revealed a gradient of individual quality from nonbreeders, to unsuccessful breeders, to successful breeders. The survival rates of unsuccessful breeders (0.90 +/- 0.023, mean +/- SE) tended to decrease in years of high average breeding success and were more sensitive to oceanographic variation than those of both (high-quality) successful breeders (0.97 +/- 0.015) and (low-quality) nonbreeders (0.83 +/- 0.028). Overall, our results indicate that reproductive costs act on individuals of intermediate quality and are mediated by environmental harshness. 相似文献
232.
Sophie Quérouil Luís Freitas Irma Cascão Filipe Alves Ana Dinis Joana R. Almeida Rui Prieto Silvia Borràs José A. Matos Diogo Mendonça Ricardo S. Santos 《Marine Biology》2010,157(11):2567-2580
Several cetacean species exhibit fine-scale population structure despite their high dispersal capacities and the apparent continuity of the marine environment. In dolphins, most studies have focused on coastal areas and continental margins, and they revealed differentiated populations within relatively small geographic areas, sometimes in conjunction with a specialisation for different habitats (ecotypes). We analysed the population genetic structure of short-beaked common dolphins (Delphinus delphis) and Atlantic spotted dolphins (Stenella frontalis) in the Azores and Madeira, the two most isolated archipelagos of the North Atlantic. The archipelago of the Azores is divided into three groups of islands and stands 900 km away from Madeira. It is not known whether individuals migrate between groups of islands and archipelagos, nor whether distinct ecotypes are present. These questions were investigated by genetic analyses of 343 biopsy samples collected on free-ranging dolphins. The analyses consisted in sequencing part of the mitochondrial hyper-variable region, screening up to 14 microsatellite loci, and molecular sexing. Results did not unravel any population structure at the scale of the study area. Lack of differentiation matches expectations for spotted dolphins, which are transient in both archipelagos, but not for common dolphins, which are present year-round in the Azores and potentially resident. Absence of genetic structure over hundreds and even thousands of kilometres implies the existence of gene flow over much larger distances than usually documented in small delphinids, which could be achieved through individual movements. This finding indicates that population structure in oceanic habitat differs from that observed in coastal habitat. 相似文献
233.
Rocío Moreno Lluís Jover Ignacio Munilla Alberto Velando Carola Sanpera 《Marine Biology》2010,157(3):545-553
The widespread omnivory of consumers and the trophic complexity of marine ecosystems make it difficult to infer the feeding
ecology of species. The use of stable isotopic analysis plays a crucial role in elucidating trophic interactions. Here we
analysed δ15N, δ13C and δ34S in chick feathers, and we used a Bayesian triple-isotope mixing model to reconstruct the diet of a generalist predator,
the yellow-legged gull (Larus michahellis) that breeds in the coastal upwelling area off northwest mainland Spain. The mixing model indicated that although chicks
from all colonies were fed with a high percentage of fish, there are geographical differences in their diets. While chicks
from northern colonies consume higher percentages of earthworms, refuse constitutes a more important source in the diet of chicks from western colonies. The three-isotope mixing model revealed
a heterogeneity in foraging habitats that would not have been apparent if only two stable isotopes had been analysed. Moreover,
our work highlights the potential of adding δ34S for distinguishing not only between terrestrial and marine prey, but also between different marine species such as fish,
crabs and mussels. 相似文献
234.
João Paulo Silva Author Vitae Mário Santos Author Vitae Author Vitae Domingos Leitão Author Vitae Author Vitae Márcia Pinto Author Vitae Author Vitae João Alexandre Cabral Author Vitae 《Ecological modelling》2010,221(16):1954-1963
Collision with conductors and earth cables is a known impact generated by transmission power lines, however there is virtually no information on how these infrastructures might affect bird distribution in a landscape context. With this work we specifically hypothesise that transmission power lines may affect the occurrence of a threatened bird, the little bustard (Tetrax tetrax). To test this hypothesis we used a Stochastic Dynamic Methodology (StDM), analysing the effects of power lines in a landscape perspective and simulating population trends as a response to power line installation and habitat changes induced by agricultural shifts in southern Portugal. The data used in the dynamic model construction included relevant gradients of environmental conditions and was sampled during the breeding seasons of 2003-2006. Transmission power lines were significantly avoided by the little bustard and the developed StDM model showed that the distance to these utility structures is the most important factor determining breeding densities in sites with suitable habitat for the species, which possibly leads to displacement of populations and habitat fragmentation. The model simulations also provided the base to analyse the cumulative effects caused by the habitat degradation that can ultimately lead to the extinction of local populations. Within priority conservation sites, the dismantling of existing transmission lines should be considered whenever possible, in order to ensure adequate breeding habitat. The model is considered useful as an auxiliary tool to be used in environmental impact assessments, management and conservation studies. 相似文献
235.
Masako Omori Tomoyuki Watanabe Jo Takai Hiroki Takada 《International journal of occupational safety and ergonomics》2013,19(4):453-462
We report the results of 3 surveys of visual display terminal (VDT) users who took a minibreak during which they viewed a stereoscopic image of a repeating parallel pattern showing planets. The single image stereogram method employed is called Stretch EyeTM, and we evaluated the effects of Stretch EyeTM on asthenopia. An accommodative relaxation of about 1 D was observed in participants while they were gazing at the image. The employees of 2 information technology companies were evaluated according to a visual analogue scale (VAS) for subjective symptoms of asthenopia and eyesight. The results showed that Stretch EyeTM was effective in easing visual fatigue due to VDT work and it improved eyesight under working conditions. 相似文献
236.
Age effect on the antioxidant activity of Daphnia magna (Anomopoda: Daphniidae): does younger mean more sensitivity? 总被引:1,自引:0,他引:1
Alberto AC Rocío OB Fernando MJ 《Journal of environmental biology / Academy of Environmental Biology, India》2011,32(4):481-487
It has been accepted that for most species newborns and senescent organisms are more sensitive than other ages to environmental stressors. Nevertheless, it must be considered that there are several biochemical and physiological compensatory processes which are not expressed with the same magnitude during the whole life cycle. With this aim, Daphnia magna individuals of different age were exposed to hexavalent chromium, Cr (VI), at two different sublethal concentrations (0.032 and 0.0064 mg l(-1)), and the activity of some antioxidant enzymes such as catalase (CAT), superoxide dismutase (SOD), glutathione reductase (GR) and glutathione peroxidase (GPx) were evaluated during most of the life cycle of this cladoceran. The antioxidant enzymatic activity showed an inverse relationship with respect to age. The activity of CAT, GR and GPx were increased in the two treated groups, at all life stages tested. On the other hand, the activity of SOD decreased in the same groups. Both, increase and decrease in the antioxidant enzymatic activities, showed significant differences with respect to the control group, being higher for the 0.032 mg l(-1) group. The Cr (VI) LC50 was also estimated for these age groups, finding statistical differences among them. Even though adults exhibited higher responses, these enzymatic activity changes should not be interpreted as higher sensitivity, since the daphnids acute chromium toxicity followed a different pattern, with increasing LC50 values according to age. 相似文献
237.
The probabilistic approach to the evaluation of fire hazard and the effectiveness of fire-precaution measures enables a rational response to the randomness of fire outbreaks. This article employs the statistical analysis methods to elucidate the causes for the ignition of fire on a random sample of industrial buildings in the Republic of Slovenia. The analyses are based on the Structural Equation Modeling (SEM), which is a well established and important statistical analysis technique in the fields of social science, biology, psychology and medicine, but hitherto rarely applied in safety research. The results of the study demonstrate that for the analyzed random sample of industrial buildings the frequency of fire outbreaks statistically significantly depends only on the presence and the probability of exposure to the heat sources (flames, sparks, and hot surfaces), but does not significantly depend on the available quantity of flammable materials within the industrial structure. 相似文献
238.
Paradelo R Villada A Devesa-Rey R Moldes AB Domínguez M Patiño J Barral MT 《Journal of environmental monitoring : JEM》2011,13(1):201-211
Trace element contamination is one of the main problems linked to the quality of compost, especially when it is produced from urban wastes, which can lead to high levels of some potentially toxic elements such as Cu, Pb or Zn. In this work, the distribution and bioavailability of five elements (Cu, Zn, Pb, Cr and Ni) were studied in five Spanish composts obtained from different feedstocks (municipal solid waste, garden trimmings, sewage sludge and mixed manure). The five composts showed high total concentrations of these elements, which in some cases limited their commercialization due to legal imperatives. First, a physical fractionation of the composts was performed, and the five elements were determined in each size fraction. Their availability was assessed by several methods of extraction (water, CaCl(2)-DTPA, the PBET extract, the TCLP extract, and sodium pyrophosphate), and their chemical distribution was assessed using the BCR sequential extraction procedure. The results showed that the finer fractions were enriched with the elements studied, and that Cu, Pb and Zn were the most potentially problematic ones, due to both their high total concentrations and availability. The partition into the BCR fractions was different for each element, but the differences between composts were scarce. Pb was evenly distributed among the four fractions defined in the BCR (soluble, oxidizable, reducible and residual); Cu was mainly found in the oxidizable fraction, linked to organic matter, and Zn was mainly associated to the reducible fraction (iron oxides), while Ni and Cr were mainly present almost exclusively in the residual fraction. It was not possible to establish a univocal relation between trace elements availability and their BCR fractionation. Given the differences existing for the availability and distribution of these elements, which not always were related to their total concentrations, we think that legal limits should consider availability, in order to achieve a more realistic assessment of the risks linked to compost use. 相似文献
239.
Almeida C Pereira C Gomes T Bebianno MJ Cravo A 《Journal of environmental monitoring : JEM》2011,13(9):2559-2567
DNA damage was evaluated in the haemolymph of Mytilus galloprovincialis from nine sites along the south coast of Portugal using the comet assay. DNA damage was low, in the same range of sites considered to suffer low impact from genotoxic contaminants. Even so, differences between sites, seasons and genders were found. Highest values were in mussels from the main estuaries and the fishery harbour, reflecting higher genotoxin levels, whereas the lowest values can be used as a baseline for future work. Non-contaminant related factors (e.g. temperature and oxygen) were also shown to influence DNA damage. Between seasons, highest values were in summer related not only to the increase of tourism in this region (~10-fold), but also to temperature. Between genders, males were found to be more sensitive. The condition index was also generally higher in summer. Lipid peroxidation, another damage biomarker, was measured in gills to assess if there is any association between the responses of both biomarkers and if they are similarly affected by the same environmental conditions. LPO like DNA damage was higher in summer. This work confirms that DNA damage is a sensitive biomarker to discriminate genotoxic contamination, even in areas considered to suffer low impact from genotoxins. 相似文献
240.
Francisco Leitão Miguel N. Santos Karim Erzini Carlos Costa Monteiro 《Marine Biology》2008,153(6):1233-1244
There is a concern that artificial reefs (AR) may act purely as fishing aggregation devices. Predators attracted to ARs can
influence the distribution and abundance of prey fish species. Determining the role of predators in AR is important in advancing
the understanding of community interactions. This paper documents the effects of predation on fish assemblages of AR located
near a coastal lagoon fish nursery. The Dicentrarchus labrax is a very opportunistic species preying on juveniles (0+ and 1+ age classes) of several demersal fish species on the ARs. Reef prey and sea bass abundance were negatively correlated. The
mean numbers of prey per sea bass stomach increased with the increase of reef fish prey abundance, suggesting that predation
has a significant influence, resulting in a decrease in prey abundance. Prey mortality (4–48%) of demersal reef fish associated
species depends on bass density. Prey selection was related both with prey abundance and vulnerability. Results showed that
D. labrax predation on AR-fish associated species can increase prey natural mortality. However, the role of bass predation on the ecological
functioning of exploited ARs is not clear. There may be increases in local fishing yields due either to an increase in predator
biomass through aggregation of sea bass attracted to ARs or to greater production. In contrast, predation on juveniles of
economically important reef fish preys, especially the most frequent and abundant (Boops boops), can contribute to a decrease in recruitment to the fishery. Our results indicate that inter-specific interactions (predator–prey)
are important in terms of conservation and management, as well as for the evaluation of the long-term effects of reef deployment.
Thus, it is necessary to consider ecological interactions, such as predation, prior to the development and deployment of artificial
habitats as a tool for rehabilitation. 相似文献