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排序方式: 共有355条查询结果,搜索用时 31 毫秒
131.
Keshavarzi B Moore F Najmeddin A Rahmani F Malekzadeh A 《Environmental geochemistry and health》2012,34(1):15-26
Golestan province in north Iran is known to be a high-risk area for esophageal cancer (EC). Of a long list of multiple risk
factors, this study focuses on a possible link between the epidemiologic patterns of EC and the anomalous concentration of
some ions and elements in the drinking water sources. A total of 183 samples from 45 villages covering a wide range of EC
mortality rates are collected and analyzed. The results demonstrate that NO3
−, SO4
2−, Sb, and Sr exceed the recommended maximum concentration level (MCL) in drinking water. This is more prominent in the villages
with high esophageal cancer mortality rate, suggesting a possible link between EC incidence and water quality. Se concentration
in drinking water increases from low to the high EC areas, a finding contrary to the expected trend. It is concluded that
Se deficiency does not play a major role in the etiology of EC in the Golestan province. The statistical results obtained
from Mann–Whitney and Kruskal–Wallis tests along with cluster analysis are consistent with the observed trend of EC mortality
rate in Golestan province. 相似文献
132.
Theory and observation indicate that changes in the rate of primary production can alter the balance between the bottom-up influences of plants and resources and the top-down regulation of herbivores and predators on ecosystem structure and function. The exploitation ecosystem hypothesis (EEH) posited that as aboveground net primary productivity (ANPP) increases, the additional biomass should support higher trophic levels. We developed an extension of EEH to include the impacts of increases in ANPP on belowground consumers in a similar manner as aboveground, but indirectly through changes in the allocation of photosynthate to roots. We tested our predictions for plants aboveground and for phytophagous nematodes and their predators belowground in two common arctic tundra plant communities subjected to 11 years of increased soil nutrient availability and/or exclusion of mammalian herbivores. The less productive dry heath (DH) community met the predictions of EEH aboveground, with the greatest ANPP and plant biomass in the fertilized plots protected from herbivory. A palatable grass increased in fertilized plots while dwarf evergreen shrubs and lichens declined. Belowground, phytophagous nematodes also responded as predicted, achieving greater biomass in the higher ANPP plots, whereas predator biomass tended to be lower in those same plots (although not significantly). In the higher productivity moist acidic tussock (MAT) community, aboveground responses were quite different. Herbivores stimulated ANPP and biomass in both ambient and enriched soil nutrient plots; maximum ANPP occurred in fertilized plots exposed to herbivory. Fertilized plots became dominated by dwarf birch (a deciduous shrub) and cloudberry (a perennial forb); under ambient conditions these two species coexist with sedges, evergreen dwarf shrubs, and Sphagnum mosses. Phytophagous nematodes did not respond significantly to changes in ANPP, although predator biomass was greatest in control plots. The contrasting results of these two arctic tundra plant communities suggest that the predictions of EEH may hold for very low ANPP communities, but that other factors, including competition and shifts in vegetation composition toward less palatable species, may confound predicted responses to changes in productivity in higher ANPP communities such as the MAT studied here. 相似文献
133.
Jennifer C. Owen Mary C. Garvin Frank R. Moore 《Behavioral ecology and sociobiology》2014,68(4):561-569
The primary cue for initiation of spring migratory restlessness (Zugunruhe) in landbird migrants is photoperiod. Gonadal hormones are known to have a role in the regulation of migratory disposition; however, the extent of their effect is not well understood. We examined the impact of exogenous testosterone on the onset of migratory restlessness in gray catbirds (Dumetella carolinensis). Catbirds were stratified by sex and randomly assigned to two rooms; individuals in one room were photoadvanced to initiate migratory restlessness and the other room was maintained on a 12:12 light/dark photoperiod. Each room had three groups (n?=?10/group); males with testosterone implants, males with empty implants, and females. We predicted that in the photoadvanced room males with testosterone implants would initiate migratory activity earlier than empty-implanted males. We found that in the photoadvanced group, testosterone-implanted males initiated migration 2 weeks prior to empty-implanted males, and 3 weeks prior to females. In the non-photoadvanced males, the testosterone-implanted males initiated migration at the same time as the corresponding group in the photoadvanced room, while the empty-implanted males and females did not exhibit Zugunruhe. Our results illustrate that elevated testosterone can advance the onset of Zugunruhe, even in the absence of an extended photoperiod. Additionally, the onset of migratory restlessness observed in the photoadvanced, non-testosterone-implanted males and females further supports the importance of photoperiod as a cue for migratory restlessness. An interesting observation was the intersexual differences in the onset of migratory activity in gray catbirds, a species not previously known to exhibit protandry. 相似文献
134.
Meier Sebastián Moore Francisca González María-Eugenia Medina Jorge Campos Pedro Khan Naser Cumming Jonathan Sanhueza Mario Mejías Jaime Morales Arturo Hirzel Juan Seguel Alex 《Environmental geochemistry and health》2021,43(4):1441-1456
Environmental Geochemistry and Health - Biochar (BC) is a porous, carbonaceous material produced by slow pyrolysis of biomass under oxygen-limited conditions. BC production has been attracting... 相似文献
135.
Naghmeh Soltani Behnam Keshavarzi Armin Sorooshian Farid Moore Christina Dunster Ana Oliete Dominguez Frank J. Kelly Prakash Dhakal Mohamad Reza Ahmadi Sina Asadi 《Environmental geochemistry and health》2018,40(5):1785-1802
Concentrations of total suspended particulate matter, particulate matter with aerodynamic diameter <2.5 μm (PM2.5), particulate matter <10 μm (PM10), and fallout dust were measured at the Iranian Gol-E-Gohar Mining and Industrial Facility. Samples were characterized in terms of mineralogy, morphology, and oxidative potential. Results show that indoor samples exceeded the 24-h PM2.5 and PM10 mass concentration limits (35 and 150 µg m?3, respectively) set by the US National Ambient Air Quality Standards. Calcite, magnetite, tremolite, pyrite, talc, and clay minerals such as kaolinite, vermiculite, and illite are the major phases of the iron ore PM. Accessory minerals are quartz, dolomite, hematite, actinolite, biotite, albite, nimite, laumontite, diopside, and muscovite. The scanning electron microscope structure of fibrous-elongated minerals revealed individual fibers in the range of 1.5 nm to 71.65 µm in length and 0.2 nm to 3.7 µm in diameter. The presence of minerals related to respiratory diseases, such as talc, crystalline silica, and needle-shaped minerals like amphibole asbestos (tremolite and actinolite), strongly suggests the need for detailed health-based studies in the region. The particulate samples show low to medium oxidative potential per unit of mass, in relation to an urban road side control, being more reactive with ascorbate than with glutathione or urate. However, the PM oxidative potential per volume of air is exceptionally high, confirming that the workers are exposed to a considerable oxidative environment. PM released by iron ore mining and processing activities should be considered a potential health risk to the mine workers and nearby employees, and strategies to combat the issue are suggested. 相似文献
136.
The application of predicted habitat models to investigate the spatial ecology of demersal fish assemblages 总被引:1,自引:0,他引:1
Benthic habitats are known to influence the abundance and richness of demersal fish assemblages; however, little is known
about how habitat structure and composition influences these distributions at very fine scales. We examined how the benthic
environment structures marine fish assemblages using high-resolution bathymetry and accurate predicted benthic habitat maps.
Areas characterised by a mosaic of habitat patches supported the highest richness of demersal fishes. A total of 37.4% of
the variation in the distribution of the fish assemblage was attributed to 6 significant variables. Depth explained 23.0%
of the variation, with the boulders explaining 12.6% and relief 1.4%. The remaining measures (seawhips, light/exposure and
solid reef) provided a small (<1.0%) but significant contribution. Identifying components of the benthic environment important
in structuring fish assemblages and understanding how they influence the spatial distribution of marine fishes is imperative
for better management of demersal fish populations. 相似文献
137.
Monica Gagliano Mark I. McCormick James A. Moore Martial Depczynski 《Marine Biology》2010,157(8):1849-1856
Ocean acidification is one of the key threats facing coral reef ecosystems, but there are few estimates of spatial and temporal
variability in pH among reef habitats. The present study documents levels of spatial variability in pH among coral reef habitats
(9 to 10), among locations separated by 100’s km of latitude and between east (Great Barrier Reef, GBR) and west (Ningaloo
Reef) coasts of Australia. Differences were found in pH between inshore and offshore waters along Ningaloo Reef (means 8.45,
8.53, respectively). Replicate assessments here ranged from 8.22 to 8.64. On the GBR, the range of values over all habitats
and replicates was 0.39 pH units (7.98 to 8.37). There were minor but significant differences of 0.05 pH units between 5 consecutive
days for habitats on average. Highest pH was recorded in filamentous algal beds maintained by the damselfish Dischistodus perspicillatus. Lowest pH was found in water extracted from sand-dwelling goby holes. While there were marked changes in pH over a 48-h
sampling period among 4 habitats at Lizard Island (GBR), there was little evidence of a diel trend. Understanding how pH varies
at scales that are relevant to organisms that live on shallow coral reefs is crucial for the design and interpretation of
experiments that test the effects on organisms of the changes in water chemistry predicted to affect oceans in the future. 相似文献
138.
Ecologists trying to understand the value of habitat to animals must first describe the value of resources contained in the habitat to animals and, second, they must describe spatial variation in resource quality at a resolution relevant to individual animal foraging. We addressed these issues in a study of koalas (Phascolarctos cinereus) in a Eucalyptus woodland. We measured beneficial and deterrent chemical characteristics as well as the palatability of trees using a near-infrared spectroscopic model based on direct feeding experiments. Tree use by koalas was influenced by tree size and foliar quality but was also context-dependent: trees were more likely to be visited if they were surrounded by small, unpalatable trees or by large, palatable trees. Spatial autocorrelation analysis and several mapping approaches demonstrated that foliar quality is spatially structured in the woodland at a scale relevant to foraging decisions by koalas and that the spatial structure is an important component of habitat quality. 相似文献
139.
Chemical communication is crucial for the organization of social insect colonies. However, with the heavy use of one communication
modality, problems may arise such as the interference of different types of information. This study investigated how information
about fertility and colony membership is integrated in the ant Camponotus floridanus. We introduced into mature, queenright colonies (a) the nestmate queen, (b) a nestmate worker, (c) a foreign, high-fertility
queen, (d) a foreign, low-fertility queen, and (e) a foreign worker. As expected, workers did not attack their nestmate queen
or a nestmate worker but responded aggressively to foreign workers and foreign, low-fertility queens. Surprisingly, workers
did not attack foreign, high-fertility queens. Chemical analysis demonstrated that the cuticular hydrocarbon profile of C. floridanus encodes information about fertility status in queens and workers and colony membership in workers. We suggest that ants respond
to this information in the cuticular hydrocarbon profile: individuals with strong fertility signals are accepted regardless
of their colony membership, but individuals without strong fertility signals are tolerated only if their cuticular hydrocarbon
profile matches that of colony members. Learning how social insects respond to multiple types of information presented together
is critical to our understanding of the recognition systems that permit the complex organization of social insect colonies. 相似文献
140.
Experts can provide valuable information to fill knowledge gaps in published research on management effectiveness, particularly for threatened ecosystems, for which there is often limited evidence and the need for prompt intervention to ensure their persistence. One such ecosystem, alpine peatland, is threatened by climate change and other pressures, provides vital ecosystem services, and supports unique biodiversity. In a workshop, we gathered and synthesized into an accessible format information from experts on interventions used, threat context, and intervention effectiveness for Australian alpine peatland and used this knowledge to evaluate local relevance of the global literature for this threatened ecosystem. Experts identified 15 interventions used to conserve Australian peatlands, most of which enhanced or restored peatland condition and effectively addressed diverse threats. Experts’ perspectives and global studies were strongly aligned, suggesting that research on peatland management may be broadly relevant across contexts, despite the distinct characteristics of Australian systems. Our workshop-based expert elicitation approach provided insights into current management practices unavailable in the literature. 相似文献