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641.
Gutiérrez-Villanueva JL Martín-Martín A Peña V Iniguez MP de Celis B de la Fuente R 《Journal of environmental radioactivity》2008,99(10):1520-1524
In situ gamma spectrometry provides a fast method to determine (137)Cs inventories in soils. To improve the accuracy of the estimates, one can use not only the information on the photopeak count rates but also on the peak to forward-scatter ratios. Before applying this procedure to field measurements, a calibration including several experimental simulations must be carried out in the laboratory. In this paper it is shown that Monte Carlo methods are a valuable tool to minimize the number of experimental measurements needed for the calibration. 相似文献
642.
Monterroso I Binimelis R Rodríguez-Labajos B 《Journal of environmental management》2011,92(3):494-507
The study described in this article incorporates stakeholders' views on aquatic invasion processes and combines expert analysis with information from field work into an evaluation exercise. Management scenarios are designed based on available technical data and stakeholders' perceptions. These scenarios are evaluated using the Social Multi-Criteria Evaluation framework employing the NAIADE model. Two evaluations are carried out, technical and social. Social acceptance of different management scenarios, distribution of costs and benefits, and attribution of responsibility are discussed. The case study was carried out on Lake Izabal, a body of water connected to the Caribbean Sea in Northeastern Guatemala. In 2000, local fishermen reported the presence of an alien species in the lake, the macrophyte Hydrilla verticillata. Two years later, this alien species was established around the entire lakeshore, damaging the ecosystem, endangering native species and the subsistence of local inhabitants through impacts on transportation, fishing practices, and tourism. 相似文献
643.
Three different systems of designating protected areas in a Mediterranean region in southeastern Spain were studied, referring
to their effectiveness and efficiency for protecting both the breeding territories and the suitable habitat of a set of ten
raptor species. Taking into consideration the varying degrees of endangerment of these species, a map of multispecies conservation
values was also drawn up and superimposed on the three protected-area systems studied. In order to compare the levels of protection
afforded by the three systems, we considered two indices that measured their relative effectiveness and efficiency. The effectiveness
estimated the proportion of territories or optimal habitat protected by the networks while efficiency implicitly considered
the area of each system (percentage of breeding territories or optimal habitat protected per 1% of land protected). Overall,
our results showed that the most efficient system was that formed by the set of regional parks and reserves (17 protected
breeding territories per 100 km2), although, given its small total area, it was by far the least effective (only protecting the 21% of the breeding territories
of all species and 17% of the area of high conservation value). The systems formed by the Special Protection Areas (designated
under the EU “Birds Directive”) and by the Special Conservation Areas (designated under the EU “Habitats Directive”) notably
increased the percentages of protected territories of all species (61%) and area of high conservation value (57%), but their
efficiency was not as high as expected in most cases. The overall level of protection was high for all species except for
the Lesser Kestrel (Falco naumanni), an endangered falcon that inhabits pseudo-steppe and traditional agricultural habitats, which are clearly underrepresented
in the protected-area network of the study region. 相似文献
644.
García-Llorente M Martín-López B Nunes PA González JA Alcorlo P Montes C 《Environmental management》2011,48(3):418-435
Biological invasions occur worldwide, and have been the object of ecological and socio-economic research for decades. However, the manner in which different stakeholder groups identify the problems associated with invasive species and confront invasive species management under different policies remains poorly understood. In this study, we conducted an econometric analysis of the social factors influencing willingness to pay for invasive alien species management under two different regimes: eradication and prevention in the Doñana Natural Protected Area (SW Spain). Controlling for the participation of local residents, tourists and conservationists, email and face-to-face questionnaires were conducted. Results indicated that respondents were more willing to pay for eradication than prevention; and public support for invasive alien species management was influenced by an individual’s knowledge and perception of invasive alien species, active interest in nature, and socio-demographic attributes. We concluded that invasive alien species management research should confront the challenges to engage stakeholders and accept any tradeoffs necessary to modify different conservation policies to ensure effective management is implemented. Finally, our willingness to pay estimates suggest the Department of Environment of Andalusian Government has suitable social support to meet the budgetary expenditures required for invasive alien species plans and adequate resources to justify an increase in the invasive alien species management budget. 相似文献
645.
Sardine larvae are forced to grow as fast as possible to reduce larval mortality. Thus, changes in biochemical composition
during the first steps of sardine larval growth are intended to maximize larval growth rate efficiency and survival. Protein
and RNA weight-specific growth rates were the highest and their corresponding doubling times the shortest among all the biomolecules,
reflecting the importance of fast growth during early stages of larval development. The protein percentage increased and the
carbohydrate and lipid percentages decreased during early growth until they reached, respectively, a percentage of 73.7, 3.1
and 18.0%. These percentages would represent the optimal proportion of biochemical components in sardine early larvae and
they are the result of the trade-off between, in the short term, the protein proportion necessary to optimize larval movement
and growth and, in the long term, the minimum lipid percentage necessary to guarantee energy reserves to fuel metamorphosis.
RNA/DNA ratio increases during larval growth up to an asymptotic optimal value of ≈3.5 in postflexion larvae. Nutritional
condition of sardine larvae was good and was influenced by the parental effect through the egg biochemical composition and
by the growth trajectory determined by the actual environmental conditions. 相似文献
646.
Generalized additive models were used to synthesize the data from 52 publications on the gonad growth and spawning seasonality
of Paracentrotus lividus and identify spatial and temporal patterns in the reproductive processes. According to our results, Atlantic populations
spawn in spring and develop large gonads (6.4 ± 0.2% of fresh body weight (mean ± SE)), which increase in size toward higher
latitudes. While in the Mediterranean, the gonads are smaller (3.1 ± 0.1%), possibly as the result of successive spawnings
which impede nutrients accumulating in the gonads. Differences were also observed between habitats: gonad production was higher
in seagrass meadows in the Mediterranean and in subtidal rocky substrates in the Atlantic. Food availability might cause these
variations as well as the negative correlation observed between depth and the gonad index for rocky substrates. Sex and body
size do not seem to influence greatly gonad growth. 相似文献
647.
Claudia Hollatz Leonardo Flach C. Scott Baker Fabrício R. Santos 《Marine Biology》2011,158(4):927-933
A large macrogeographic differentiation has been observed among Sotalia guianensis populations along the South American coast. However, no genetic structure has been detected so far in closely distributed
populations of this species, even though it has been observed in other cetaceans. Here, we examined the fine scale population
structure for the largest populations of S. guianensis inhabiting Sepetiba and Paraty embayments at the south-eastern coast of Rio de Janeiro, Brazil. Analysis of mitochondrial
DNA (mtDNA) control region sequences failed to detect variability among sequences. Conversely, evidence of significant male
population structure was found on the basis of ten nuclear microsatellite loci. Surprisingly, the microsatellite markers were
able to distinguish between individuals from the two embayments located 60 km apart. The results suggest that differences
in habitat type and behavioral specializations are likely to explain the patterns of genetic structure. These findings should
provide baselines for the management of communities exposed to increasing human-driven habitat loss. 相似文献
648.
John M. Logan Enrique Rodríguez-Marín Nicolas Goñi Santiago Barreiro Haritz Arrizabalaga Walter Golet Molly Lutcavage 《Marine Biology》2011,158(1):73-85
Atlantic bluefin tuna (Thunnus thynnus) are highly migratory predators whose abundance, distribution, and somatic condition have changed over the past decades.
Prey community composition and abundance have also varied in several foraging grounds. To better understand underlying food
webs and regional energy sources, we performed stomach content and stable isotope analyses on mainly juvenile (60–150 cm curved
fork length) bluefin tuna captured in foraging grounds in the western (Mid-Atlantic Bight) and eastern (Bay of Biscay) Atlantic
Ocean. In the Mid-Atlantic Bight, bluefin tuna diet was mainly sand lance (Ammodytes spp., 29% prey weight), consistent with historic findings. In the Bay of Biscay, krill (Meganyctiphanes norvegica) and anchovy (Engraulis encrasicolus) made up 39% prey weight, with relative consumption of each reflecting annual changes in prey abundance. Consumption of anchovies
apparently declined after the local collapse of this prey resource. In both regions, stable isotope analysis results showed
that juvenile bluefin tuna fed at a lower trophic position than indicated by stomach content analysis. In the Mid-Atlantic
Bight, stable isotope analyses suggested that >30% of the diet was prey from lower trophic levels that composed <10% of the
prey weights based upon traditional stomach content analyses. Trophic position was similar to juvenile fish sampled in the
NW Atlantic but lower than juveniles sampled in the Mediterranean Sea in previous studies. Our findings indicate that juvenile
bluefin tuna targeted a relatively small range of prey species and regional foraging patterns remained consistent over time
in the Mid-Atlantic Bight but changed in relation to local prey availability in the Bay of Biscay. 相似文献
649.
650.
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