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751.
We tested the prediction that lactating fur seals (Arctocephalus gazella) at South Georgia will take prey of greater energy density with increasing distance of foraging from the colony. The study
investigated the differences in diet of fur seals foraging within two regions, one near the breeding colony and the other
at greater distance. Diet varied significantly in relation to foraging location. Dietary items of low quality were eaten in
both regions but more food items with a high-energy content appeared in the diet of seals travelling to distant oceanic waters.
We conclude that there is likely to be a trade-off between energy gain and distance travelled which enables female fur seals
to maintain a relatively constant rate of energy delivery to their offspring irrespective of the distance travelled to find
food. 相似文献
752.
Radon has been determined in soil, groundwater, and air in Mexico, both indoors and outdoors, as part of geophysical studies
and to estimate effective doses as a result of radon exposure. Detection of radon has mainly been performed with solid-state
nuclear track detectors (SSNTD) and, occasionally, with active detection devices based on silicon detectors or ionization
chambers. The liquid scintillation technique, also, has been used for determination of radon in groundwater. The adjusted
geometric mean indoor radon concentration (74 Bq m−3) in urban developments, for example Mexico City, is higher than the worldwide median concentration of radon in dwellings.
In some regions, particularly hilly regions of Mexico where air pollution is high, radon concentrations are higher than action
levels and the effective dose for the general population has increased. Higher soil radon levels have been found in the uranium
mining areas in the northern part of the country. Groundwater radon levels are, in general, low. Soil-air radon contributing
to indoor atmospheres and air pollution is the main source of increased exposure of the population. 相似文献
753.
A. Triantafyllidis I. Leonardos I. Bista I. D. Kyriazis M. Th. Stoumboudi I. Kappas F. Amat T. J. Abatzopoulos 《Marine Biology》2007,152(5):1159-1167
The purpose of this study was to determine the phylogeographic structure of the brackish-hypersaline cyprinodont fish Aphanius fasciatus (Valenciennes, 1821), using sequencing and RFLP analysis of a 1,330 bp mitochondrial DNA segment containing part of the 16S
rRNA gene as well as the genes for tRNA-Leu, NADH subunit 1 and tRNA-Ile. Individuals were collected from 13 different sites
in Greece and Turkey, while seven published A. fasciatus sequences were also included to cover the area of distribution of the species. Pairwise sequence divergence values ranged
from 0 to 4.51%. Congruent phylogenies were recovered with maximum likelihood, maximum parsimony and neighbour-joining methods.
All analyses revealed two main groups. The first group consists of populations from almost all localities that drain into
the Aegean Sea. The second group comprises the remaining population samples, which in some cases seem to consist of population-specific
subgroups. Our results show that vicariant events have predominantly affected the evolution of A. fasciatus, with the Messinian salinity crisis having shaped the present genetic structure of its populations. Additionally, the life-history
traits of the species, which determine a low potential for dispersal, coupled with the typical fragmentation of brackish-hypersaline
water habitats have led to a high degree of isolation of A. fasciatus populations, even at restricted spatial scales. Analysis of the partitioning of the total amount of polymorphism with analyses
of molecular variance (AMOVA) gave a value of F
ST = 84.6%. Potential conservation policies concerning A. fasciatus should also consider the low-genetic variability in the majority of its populations and the presence of fixed haplotypes
in some of them. 相似文献
754.
Charlotte E Gonzalez-Abraham Volker C Radeloff Todd J Hawbaker Roger B Hammer Susan I Stewart Murray K Clayton 《Ecological applications》2007,17(7):2011-2023
Rural America is witnessing widespread housing development, which is to the detriment of the environment. It has been suggested to cluster houses so that their disturbance zones overlap and thus cause less habitat loss than is the case for dispersed development. Clustering houses makes intuitive sense, but few empirical studies have quantified the spatial pattern of houses in real landscapes, assessed changes in their patterns over time, and quantified the resulting habitat loss. We addressed three basic questions: (1) What are the spatial patterns of houses and how do they change over time; (2) How much habitat is lost due to houses, and how is this affected by spatial pattern of houses; and (3) What type of habitat is most affected by housing development. We mapped 27 419 houses from aerial photos for five time periods in 17 townships in northern Wisconsin and calculated the terrestrial land area remaining after buffering each house using 100- and 500-m disturbance zones. The number of houses increased by 353% between 1937 and 1999. Ripley's K test showed that houses were significantly clustered at all time periods and at all scales. Due to the clustering, the rate at which habitat was lost (176% and 55% for 100- and 500-m buffers, respectively) was substantially lower than housing growth rates, and most land area was undisturbed (95% and 61% for 100-m and 500-m buffers, respectively). Houses were strongly clustered within 100 m of lakes. Habitat loss was lowest in wetlands but reached up to 60% in deciduous forests. Our results are encouraging in that clustered development is common in northern Wisconsin, and habitat loss is thus limited. However, the concentration of development along lakeshores causes concern, because these may be critical habitats for many species. Conservation goals can only be met if policies promote clustered development and simultaneously steer development away from sensitive ecosystems. 相似文献
755.
M. I. Silva H. D. Burrows S. J. Formosinho L. Alves A. Godinho M. J. Antunes D. Ferreira 《Environmental Chemistry Letters》2007,5(3):143-149
Advanced oxidation processes, such as photocatalysed oxidation, provide an important route for degradation of wastes. In this
study, the lowest excited state (3MLCT) of Ru(bpy)32+ is used to break down chlorophenol pollutant molecules to harmless products. This has the advantage of using visible light
and a short-lived catalytically active species. Photolysis of deaerated aqueous solutions of a variety of mono- and poly-substituted
chlorophenols has been followed in the presence of Ru(bpy)32+/S2O82− with near visible light (λ > 350 nm) by UV/visible absorption spectroscopy, luminescence, potentiometry, NMR and HPLC techniques.
Upon irradiation, a decrease is observed in the chlorophenol concentration, accompanied by the formation of Cl−, H+ and SO42− ions as the main inorganic products. Benzoquinone, phenol, dihydroxybenzenes and chlorinated compounds were the dominant
organic products. As the ruthenium(II) complex is regenerated in the reaction, the scheme corresponds to an overall catalytic
process. The kinetics of the rapid chlorophenol photodechlorination has been studied, and are described quite well by pseudo-first
order behaviour. Further studies on this were made by following Cl− release with respect to the initial Ru(bpy)32+ and S2O82− concentrations. A comparison is presented of the photodechlorination reactivity of the mono and polychlorophenols studied
at acidic and alkaline pH. 相似文献
756.
O. Barneah I. Brickner M. Hooge V. M. Weis T. C. LaJeunesse Y. Benayahu 《Marine Biology》2007,151(4):1215-1223
Epizoic worms were found to occur on certain coral colonies from reefs off the coast of Eilat (Red Sea). We identified 14
coral species infested by acoelomorph worms at a depth range of 2–50 m. The host corals were all zooxanthellate and included
both massive and branching stony corals and a soft coral. Worms from all hosts were identified as belonging to the genus Waminoa and contained two distinct algal symbionts differing in size. The smaller one was identified as Symbiodinium sp. and the larger one is presumed to belong to the genus Amphidinium. Worm-infested colonies of the soft coral, Stereonephthya cundabiluensis, lacked a mucus layer and exhibited distinct cell microvilli, a phenotype not present in colonies lacking Waminoa sp. In most cases, both cnidarian and Acoelomorph hosts displayed high specificity for genetically distinctive Symbiodinium spp. These observations show that the epizoic worms do not acquire their symbionts from the “host” coral. 相似文献
757.
Sampling design trade-offs in occupancy studies with imperfect detection: examples and software. 总被引:2,自引:0,他引:2
Larissa L Bailey James E Hines James D Nichols Darryl I MacKenzie 《Ecological applications》2007,17(1):281-290
Researchers have used occupancy, or probability of occupancy, as a response or state variable in a variety of studies (e.g., habitat modeling), and occupancy is increasingly favored by numerous state, federal, and international agencies engaged in monitoring programs. Recent advances in estimation methods have emphasized that reliable inferences can be made from these types of studies if detection and occupancy probabilities are simultaneously estimated. The need for temporal replication at sampled sites to estimate detection probability creates a trade-off between spatial replication (number of sample sites distributed within the area of interest/inference) and temporal replication (number of repeated surveys at each site). Here, we discuss a suite of questions commonly encountered during the design phase of occupancy studies, and we describe software (program GENPRES) developed to allow investigators to easily explore design trade-offs focused on particularities of their study system and sampling limitations. We illustrate the utility of program GENPRES using an amphibian example from Greater Yellowstone National Park, U.S.A. 相似文献
758.
Sather ME Slonecker ET Mathew J Daughtrey H Williams DD 《Environmental monitoring and assessment》2007,124(1-3):211-221
Nitrogen Dioxide (NO2) is a common urban air pollutant that results from the combustion of fossil fuels. It causes serious human health effects,
is a precursor to the formation of ground level ozone, another serious air pollutant, and is one of the six criteria air pollutants
established by the United States (U.S.) Clean Air Act (CAA). Ogawa Passive Sampling Devices (PSDs) for NO2 were collocated and operated at six NO2 Federal Reference Method (FRM) monitor locations in the El Paso, Texas area for the 2004 calendar year. Passive samples were
taken at 2-week, 3-week, and 4-week intervals and compared against the continuously operating FRM monitors. Results showed
that the collective NO2 annual arithmetic mean for all passive monitors was identical to the NO2 mean for all FRM monitors. Of the individual locations, three passive annual NO2 means were identical to their corresponding FRM means, and three passive annual NO2 means differed from their corresponding FRM means by only one part per billion (ppb). Linear correlation analysis between
all readings of the individual NO2 PSDs and FRM values showed an average absolute difference of 1.2 ppb with an r
2 of 0.95. Paired comparison between high and low concentration annual NO2 sites, seasonal considerations, and interlab quality control comparisons all showed excellent results. The ease of deployment,
reliability, and the cost-savings that can be realized with NO2 PSDs could make them an attractive alternative to FRM monitors for screening purposes, and even possibly an equivalent method
for annual NO2 monitoring. More tests of the Ogawa NO2 PSD are recommended for different ecosystem and climate regimes. 相似文献
759.
Rao PS Ansari MF Gavane AG Pandit VI Nema P Devotta S 《Environmental monitoring and assessment》2007,128(1-3):323-328
Petroleum refineries are largest chemical industries that are responsible for the emission of several pollutants into the
atmosphere. Benzene is among the most important air pollutants that are emitted by petroleum refineries, since they are involved
in almost every refinery process. Volatile organic compounds (VOCs) are a major group of air pollutants, which play a critical
role in atmospheric chemistry. These contribute to toxic oxidants, which are harmful to ecosystem, human health and atmosphere.
The variability of pollutants is an important factor in determining human exposure to these chemicals. The ambient air concentrations
of benzene were measured in several sites around the Digboi petroleum refinery, near the city of Gowahati in northeast India,
during winter and summer 2004. The seasonal and spatial variations of the ambient air concentrations of this benzene were
investigated and analyzed. An estimation of the contribution of the refinery to the measured atmospheric levels of benzene
was also performed. The ambient air mixing ratios of benzene in a large area outside the refinery was generally low, in ppbv
range, much lower than the ambient air quality standards. This article presents the temporal and spatial variation of air
pollution in and around petroleum refinery and showed that no health risk due to benzene is present in the areas adjacent
to the refinery. 相似文献
760.