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571.
Keith W. Sockman Jack Weiss Michael S. Webster Vanessa Talbott Hubert Schwabl 《Behavioral ecology and sociobiology》2008,62(4):617-625
Maternally derived androgen hormones concentrate in avian egg yolks as the yolks grow on the female’s ovary, possibly forming
a basis for important maternal effects in birds. In the American kestrel (Falco sparverius), experimental elevation of yolk androgens in the first-laid egg of a clutch (a-egg) to the concentrations found naturally
in a clutch’s later-laid eggs reduces the growth rate of a-egg nestlings compared to controls. These findings, together with
discoveries from other species that the effects of yolk androgens on growth of female nestlings may differ from their effects
on growth of male nestlings, raise the hypothesis that natural changes in yolk-androgen concentrations with laying order are
ultimately due to a difference between the sexes in their yolk-androgen sensitivity and between early- and late-laid eggs
in their sex ratio. By re-analyzing previously published data and adding to the analysis data from previously unanalyzed blood
samples used for sex determination, we investigated possible sex-specific effects of yolk-androgens in the context of a potential
sex-biased laying order in free-living American kestrels. We used a multi-level, mixed model with a Gompertz function to analyze
growth of nestlings hatching from a-eggs that were control-treated or in which we experimentally elevated yolk-androgen concentrations
shortly after laying to the higher concentrations naturally found in later-laid eggs. We discovered that male nestlings were
more susceptible than female nestlings to growth inhibition by yolk-androgen elevation but did not find a bias in sex ratio
with respect to laying order. Together, these findings do not support the above hypothesis. However, they are consistent with
the hypothesis that sex differences in yolk-androgen sensitivity enable mothers to economically tune reproductive effort to
an individual offspring’s reproductive value, which can vary more for one sex than the other. 相似文献
572.
Radeloff VC Nelson E Plantinga AJ Lewis DJ Helmers D Lawler JJ Withey JC Beaudry F Martinuzzi S Butsic V Lonsdorf E White D Polasky S 《Ecological applications》2012,22(3):1036-1049
Land-use change significantly contributes to biodiversity loss, invasive species spread, changes in biogeochemical cycles, and the loss of ecosystem services. Planning for a sustainable future requires a thorough understanding of expected land use at the fine spatial scales relevant for modeling many ecological processes and at dimensions appropriate for regional or national-level policy making. Our goal was to construct and parameterize an econometric model of land-use change to project future land use to the year 2051 at a fine spatial scale across the conterminous United States under several alternative land-use policy scenarios. We parameterized the econometric model of land-use change with the National Resource Inventory (NRI) 1992 and 1997 land-use data for 844 000 sample points. Land-use transitions were estimated for five land-use classes (cropland, pasture, range, forest, and urban). We predicted land-use change under four scenarios: business-as-usual, afforestation, removal of agricultural subsidies, and increased urban rents. Our results for the business-as-usual scenario showed widespread changes in land use, affecting 36% of the land area of the conterminous United States, with large increases in urban land (79%) and forest (7%), and declines in cropland (-16%) and pasture (-13%). Areas with particularly high rates of land-use change included the larger Chicago area, parts of the Pacific Northwest, and the Central Valley of California. However, while land-use change was substantial, differences in results among the four scenarios were relatively minor. The only scenario that was markedly different was the afforestation scenario, which resulted in an increase of forest area that was twice as high as the business-as-usual scenario. Land-use policies can affect trends, but only so much. The basic economic and demographic factors shaping land-use changes in the United States are powerful, and even fairly dramatic policy changes, showed only moderate deviations from the business-as-usual scenario. Given the magnitude of predicted land-use change, any attempts to identify a sustainable future or to predict the effects of climate change will have to take likely land-use changes into account. Econometric models that can simulate land-use change for broad areas with fine resolution are necessary to predict trends in ecosystem service provision and biodiversity persistence. 相似文献
573.
Hierarchical regulation of nitrogen export from urban catchments: interactions of storms and landscapes. 总被引:1,自引:0,他引:1
In urban catchments of arid central Arizona, we investigate how the export of mineral and organic nitrogen (N) in storm runoff is regulated by interactions between local landscape characteristics and broader scale storm features. First, we test whether N export is more a function of (1) processes that affect N concentration in runoff or (2) the propensity of the catchment to convey rainfall as runoff. With data pooled across catchments, the mass of N in export (load) is determined by processes regulating runoff N concentration. There are exceptions when catchments are examined individually, where N load from some catchments is determined by the hydrologic responsiveness of the catchment. Second, we investigate the relationship between N export and catchment features. Loads per catchment area were greater from more impervious catchments, probably because impervious catchments held more N in a mobilizable phase and conveyed more rainfall as overland flow. Loads per area were lower from larger catchments, possibly owing to more N-retention hot spots in larger catchments. Catchments with the greatest N exports were those with commercial land use, and loads decreased as development became less prevalent or as residential replaced industrial land use. Third, we investigated how catchment features moderated direct responses of N export to storms. Export was less correlated with storm features in catchments that were larger, more pervious, and less industrial. Results support an "N build and flush" hypothesis, which purports that there is little biotic processing of N deposited to arid, urban surfaces with little organic matter. The rate and duration of deposition determine the size of the mobile N pool. Any amount of rainfall capable of generating overland flow would entrain nearly all mobilizable N and export it from the catchment. Nonetheless, these results suggest that, even with daunting seasonal and interannual variability in storm conditions, material export can be reduced by managing intrinsic catchment features. 相似文献
574.
Saskia Van Gaever Leon Moodley Francesca Pasotti Marco Houtekamer Jack J. Middelburg Roberto Danovaro Ann Vanreusel 《Marine Biology》2009,156(6):1289-1296
We report the results of a detailed investigation on the trophoecology of two dominant meiofaunal species at the Håkon Mosby Mud Volcano (HMMV), a deep-sea cold methane-venting seep. Analyses of fatty acids (FAs) and their stable carbon isotopes were used to determine the importance of chemosynthetic nutritional pathways for the dominant copepod species (morphologically very similar to Tisbe wilsoni) inhabiting the volcano’s centre and the abundant nematode Halomonhystera disjuncta from the surrounding microbial mats. The strong dominance of bacterial biomarkers (16:1ω7c, 18:1ω7c and 16:1ω8c) coupled with their individual light carbon isotopes signatures (δ13C ranging from ?52 to ?81‰) and the lack of symbiotic relationships with prokaryotes (as revealed by molecular analyses and fluorescent in situ hybridisation) indicated that chemosynthetically derived carbon constitutes the main diet of both species. However, the copepod showed a stronger reliance on the utilisation of methanotrophic bacteria and contained polyunsaturated FAs of bacterial origin (20:5ω3 and 22:6ω3 with isotope signatures δ13C < ?80‰). Instead, the FA profiles of H. disjuncta suggested that sulphide-oxidising bacteria constituted the main diet of this nematode. Therefore, HMMV can be regarded as a persistent deep-sea cold seep, allowing a chemosynthesis-based trophic specialisation by the dominant meiofaunal species inhabiting its sediments. The present investigation, through the determination of the fatty acid profiles, provides the first evidence for trophic specialisation of meiofauna associated with sub-habitats within a cold seep. 相似文献
575.
Pilar Santidrián Tomillo Jack S. Suss Bryan P. Wallace Kimberly D. Magrini Gabriela Blanco Frank V. Paladino James R. Spotila 《Marine Biology》2009,156(10):2021-2031
Reproductive output of leatherback turtles (Dermochelys coriacea) is affected by the stochastic nature of emergence success. Average emergence success of nests at Playa Grande, Costa Rica
was 0.38 ± 0.27. Incubation temperature affected development of leatherback turtle eggs and emergence of hatchlings from the
nest. We found that high temperatures reduced hatching success and emergence rate and increased embryonic mortality both early
and late during incubation at Playa Grande. There was a temporal effect on emergence success that resulted in more hatchlings
being produced at the beginning of the season, because of higher emergence success, than toward the end. Likewise, production
of hatchlings varied from year to year. The average annual reproductive output was 252 ± 141 hatchlings per female. The 2005–2006
nesting season had the highest emergence success and produced the greatest number of hatchlings per female compared to the
2004–2005 (+120%) and 2006–2007 (+41%) seasons. However, average clutch size (62 ± 10) and clutch frequency (9.45 ± 1.63),
were not different among years. Turtles that had nested a high number of years exhibited greater clutch frequency and arrived
earlier to nest than turtles that had nested in fewer numbers of years. Nesting when environmental conditions favor high developmental
success and emergence rate may constitute an advantageous reproductive strategy. 相似文献
576.
Ocean acidification is not happening in isolation but against a background of chronic low-level pollution for most coastal marine environments. The reproductive and larval stages of marine invertebrates can be highly sensitive to the impacts of both environmental pollutants and ocean acidification, but very little is currently known regarding the potential impacts of combined contaminant and high CO2 exposures on the health of marine organisms. Ocean acidification research to date has focused heavily on the responses of calcifying marine invertebrate larvae and algae, and as such the polychaetes as a group, despite their ecological importance, remain understudied. Here, we investigate the effects of elevated seawater CO2 (pH range 8.1–7.4, plus an extreme pH of 7.2 in the sperm motility experiments), in combination with the environmental pollutant copper (0.002 μM), on the early life history stages of the intertidal polychaete Pomatoceros lamarckii from two populations. P. lamarckii sperm appear to be robust to elevated seawater CO2. Whilst all three of the sperm motility end points measured showed a response to elevated CO2, these responses were small and not linear. The percentage of motile sperm and sperm curvilinear velocity were significantly reduced in the lower pH treatments of 7.4 and 7.2, whereas sperm straight-line velocity (VSL) was mostly unaffected except for an increased VSL at pH 8.0. Fertilisation success was investigated using two populations from the South West (UK), one from Torquay and one from Plymouth Sound. Fertilisation success was slightly but significantly reduced at the 7.6 and 7.4 pH treatments for both populations (a 9.0 % reduction in fertilisation success from pH 8.1 to 7.4 for Torquay), but with a greater effect observed in the population from Plymouth Sound (a 13.33 % reduction in fertilisation success). No additional impact of 0.002 μM copper exposure on fertilisation success was found. Larval survival was found to be much more sensitive to elevated CO2 than sperm function or fertilisation, and a significant interaction with copper exposure was observed. These results demonstrate the potential for polychaete larvae to be affected by predicted ocean acidification conditions and that chronic coastal pollutants, such as copper, have the potential to alter larval susceptibility to ocean acidification conditions. 相似文献
577.
Violet Diacomanolis Barry N. Noller Jack C. Ng 《Environmental geochemistry and health》2013,35(6):757-766
Arsenic (As) and lead (Pb) are common contaminants found in mine waste materials. For an evidence-based risk assessment, it is important to better understand the potential interaction of mixed contaminants; and this interaction study was investigated in an in vivo rat model. Following co-administration of a fixed dose of AsV as in sodium arsenate and different doses of Pb as lead acetate to Sprague–Dawley rats, blood arsenic concentration and bioavailability decreased. A decrease in As blood concentration when lead was co-administered was observed with increasing lead doses. Pharmacokinetic parameters for As in the blood showed faster absorption and elimination of this metalloid in the presence of Pb. The elimination half-life of As decreased from 67 days in As solo group to 27–30 with doses of Pb. Bioavailability of As was also decreased by 30–43 % in the presence of Pb. Decreased urinary excretion of Pb and tissue accumulation were also observed. It indicates lower absorption of As when co-administered with Pb. A probable explanation for these findings is that As co-administration with Pb could have resulted in the formation of less soluble lead arsenate. However, such an interaction between As and Pb could only explain about one-third of the variation when real mine waste materials containing both of these elements were administered to rats. This suggests that other effects from physical and chemical parameters could contribute to the bioavailability of arsenic in complex real environmental samples. 相似文献
578.
Local and interregional economic analysis of large US Department of Energy waste management projects
An economic simulation model was used to understand the local and interregional economic impacts of four alternative waste management technologies proposed for the US Department of Energy's Savannah River nuclear weapons site. The simulations of the four technologies, each of which will cost at least a billion dollars, were done for the period 2000-2015. The analyses show that differences in project costs are not directly reflected in local economic impacts because of differences among the technologies during the design, testing and construction phases; differences in locations where the design and pilot-testing would occur; and choices about how any of the technologies would be funded. 相似文献
579.
The evolution of NOx from grass and maize silages wasmeasured using chemiluminescence in samples kept in airtightcontainers, in the silos and in a 750 kg mass removed to a mixer waggon. Measurements were made on the grass and maizesilos in two consecutive years. The results show that thereis continuous evolution of NOx after silos have been opened and that high concentrations persist in the mass whichare rapidly released on agitation at the feed-out. The maximumrecorded concentrations of NO and NO2 were 1985 and 152 ppbv respectively. These values are orders of magnitude greaterthan for rural background levels and exceed the maximum hourlyexposure of 50 ppbv for NO2 recommended by the UK expertpanel for quality standards. 相似文献
580.
Bioremediation of soils contaminated with explosives 总被引:3,自引:0,他引:3
The large-scale industrial production and processing of munitions such as 2,4,6-trinitrotoluene (TNT) over the past 100 years led to the disposal of wastes containing explosives and nitrated organic by-products into the environment. In the US, the Army alone has estimated that over 1.2 million tons of soil have been contaminated with explosives, and the impact of explosives contamination in other countries is of similar magnitude. In recent years, growing concern about the health and ecological threats posed by man-made chemicals have led to studies of the toxicology of explosives, which have identified toxic and mutagenic effects of the common military explosives and their transformation products (Bruns-Nagel et al., 1999a; Fuchs et al., 2001; Homma-Takeda et al., 2002; Honeycutt et al., 1996; Rosenblatt et al., 1991; Spanggord et al., 1982; Tan et al., 1992 and Won et al., 1976). Because the cleanup of areas contaminated by explosives is now mandated because of public health concerns, considerable effort has been invested in finding economical remediation technologies. Biological treatment processes are often considered, since these are usually the least expensive means of destroying organic pollution. This review examines the most important groups of chemicals that must be treated at sites contaminated by explosives processing, the chemical and biological transformations they undergo, and commercial processes developed to exploit these transformations for treatment of contaminated soil. We critically examine about 150 papers on the topic, including approximately 60 published within the past 5 years. 相似文献