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Wakefield R Tyler AN McDonald P Atkin PA Gleizon P Gilvear D 《Journal of environmental radioactivity》2011,102(3):252-261
High spatial and temporal resolution airborne imagery were acquired for the Ribble Estuary, North West England in 1997 and 2003, to assess the application of time-series airborne remote sensing to quantify total suspended sediment and radionuclide fluxes during a flood and ebb tide sequence. Concomitant measurements of suspended particulate matter (SPM) and water column turbidity were obtained during the time-series image acquisition for the flood and ebb tide sequence on the 17th July 2003 to verify the assumption of a vertically well mixed estuary and thus justifying the vertical extrapolation of spatially integrated estimate of surface SPM. The 137Cs activity concentrations were calculated from a relatively stable relationship between SPM and 137Cs for the Ribble Estuary. Total estuary wide budgets of sediment and 137Cs were obtained by combining the image-derived estimates of surface SPM and 137Cs with estimates of water volume from a two-dimensional hydrodynamic model (VERSE) developed for the Ribble Estuary. These indicate that around 10,000 tonnes of sediment and 2.72 GBq of 137Cs were deposited over the tidal sequence monitored in July 2003. This compared favourably with bed height elevation change estimated from field work. An uncertainty analysis on the total sediment and 137Cs flux yielded a total budget of the order of 40% on the final estimate. The results represent a novel approach to providing a spatially integrated estimate of the total net sediment and radionuclide flux in an intertidal environment over a flood and ebb tide sequence. 相似文献
2.
Through two-choice gustatory experiments, a␣preference hierarchy was established␣for␣the␣herbivorous gastropod Norrisianorrisi Sowerby, with laminarialean kelps preferred over all other seaweeds. Among the kelps, laminae of Macrocystispyrifera were slightly preferred over Egregiamenziesii, and both were strongly preferred over sporophylls of Eiseniaarborea. E.arborea, the least preferred kelp, was consistently chosen over other algae common in the snail's habitat (Halidrysdioica, Dictyotaflabellata, and Pterocladiacapillacea) and over seaweeds believed to be edible and palatable based on their morphology, structure, and secondary chemistry (Endarachnebinghamiae, Mazzaellaflaccida, and Ulvalobata). The morphologies and structural toughness of tested seaweeds varied significantly as did their nutritional (% carbon, %
nitrogen, C:N ratio, and % ash) contents and phlorotannin concentrations; however, snails preferred to feed on kelps regardless
of nutritional content, toughness or phlorotannin concentration; and among kelps preferred to feed on the least tough species
(based on penetrometer measurements), which also were those containing the lowest phlorotannin concentrations. Preference
for kelp was not upheld in experiments using agarose thalli to which freeze-dried powder, of either the kelp Eiseniaarborea or non-kelp Endarachnebinghamiae was added, suggesting the destruction of attractant chemicals during the making of the artificial foods. Our data suggest
that the preference of N. norrisi for kelps over other potentially edible and palatable seaweeds may not be related to nutritional content, but instead may
have evolved in response to factors such as availability, habitat provision, or refuge from predation.
Received: 27 September 1996 / Accepted: 7 October 1997 相似文献
3.
Mary B. Janicki Christopher G. Fernandez Dorothy Wakefield Jonathan P. Shepherd Reinaldo Figueroa 《黑龙江环境通报》2020,40(2):223-231
To determine if using a checklist of specific ultrasound image criteria to screen the fetal heart improves the cardiac exam completion rate, defined as the ability to classify the heart as normal or abnormal. This is a retrospective cohort study of patients with singleton pregnancies who underwent a fetal anatomy survey between 18 and 28 weeks' gestation. A checklist was used from 1 September 2015 to 31 March 2016 to categorize exams as complete-normal, complete-abnormal, or incomplete. Performance was compared with a 7-month period prior to checklist introduction (1 December 2014 to 30 June 2015). Checklist utilization improved the cardiac exam completion rate by 8.9%. With the checklist, 1083 of 1202 exams (90.1%) were completed compared to 987 of 1193 (82.7%) pre-checklist, P < .001. We did not detect a change in cases classified as abnormal and referred for echocardiography: 25 (2.1%) with the checklist and 16 (1.3%) pre-checklist, P = .16. We did not detect more congenital heart disease (CHD), 12 (1.0%) with checklist screening, 5 (0.4%) pre-checklist, P = .14. Critical CHD was not missed in either group. Using the checklist improved the cardiac exam completion rate. There was no change in congenital heart disease detection. 相似文献
4.
Nestor E. Bosch Jacquomo Monk Jordan Goetze Shaun Wilson Russell C. Babcock Neville Barrett Jock Clough Leanne M. Currey-Randall David V. Fairclough Rebecca Fisher Brooke A. Gibbons David Harasti Euan S. Harvey Michelle R. Heupel Jamie L. Hicks Thomas H. Holmes Charlie Huveneers Daniel Ierodiaconou Alan Jordan Nathan A. Knott Hamish A. Malcolm Dianne McLean Mark Meekan Stephen J. Newman Ben Radford Matthew J. Rees Benjamin J. Saunders Conrad W. Speed Michael J. Travers Corey B. Wakefield Thomas Wernberg Tim J. Langlois 《Conservation biology》2022,36(2):e13807
Marine fisheries in coastal ecosystems in many areas of the world have historically removed large-bodied individuals, potentially impairing ecosystem functioning and the long-term sustainability of fish populations. Reporting on size-based indicators that link to food-web structure can contribute to ecosystem-based management, but the application of these indicators over large (cross-ecosystem) geographical scales has been limited to either fisheries-dependent catch data or diver-based methods restricted to shallow waters (<20 m) that can misrepresent the abundance of large-bodied fished species. We obtained data on the body-size structure of 82 recreationally or commercially targeted marine demersal teleosts from 2904 deployments of baited remote underwater stereo-video (stereo-BRUV). Sampling was at up to 50 m depth and covered approximately 10,000 km of the continental shelf of Australia. Seascape relief, water depth, and human gravity (i.e., a proxy of human impacts) were the strongest predictors of the probability of occurrence of large fishes and the abundance of fishes above the minimum legal size of capture. No-take marine reserves had a positive effect on the abundance of fishes above legal size, although the effect varied across species groups. In contrast, sublegal fishes were best predicted by gradients in sea surface temperature (mean and variance). In areas of low human impact, large fishes were about three times more likely to be encountered and fishes of legal size were approximately five times more abundant. For conspicuous species groups with contrasting habitat, environmental, and biogeographic affinities, abundance of legal-size fishes typically declined as human impact increased. Our large-scale quantitative analyses highlight the combined importance of seascape complexity, regions with low human footprint, and no-take marine reserves in protecting large-bodied fishes across a broad range of species and ecosystem configurations. 相似文献
5.
This article explores individual and community action taken in response to perceived environmental risks by investigating
the determinants of environmental action across a range of action types. A conceptual framework is first presented, which
provides a foundation for investigating the role of local compositional (i.e., individual characteristics), contextual (i.e.,
neighborhood environment), and collective (i.e., social networks) factors in environmental action. To test the utility of
the conceptual framework, a quantitative survey was administered to a random sample of households (n = 512) in Hamilton, Canada.
The results suggest that the predictors of environmental action vary by action type (i.e., personal change, individual civic
action, and cooperative civic action), and that factors related to perceived environmental exposure and social capital generally
play a stronger, more consistent role in civic environmental action than sociodemographic or neighborhood factors. The results
underscore the role of social connection in responses to perceived environmental risks. 相似文献
6.
In this article, the mathematical assumptions of a number of commonly used ecological regression models are made explicit, critically assessed, and related to ecological bias. In particular, the role and interpretation of random effects models are examined. The modeling of spatial variability is considered and related to an underlying continuous spatial field. The examination of such a field with respect to the modeling of risk in relation to a point source highlights an inconsistency in commonly used approaches. A theme of the paper is to examine how plausible individual-level models relate to those used in practice at the aggregate level. The individual-level models acknowledge confounding, within-area variability in exposures and confounders, measurement error and data anomalies and so we can examine how the area-level versions consider these aspects. We briefly discuss designs that efficiently sample individual data and would appear to be useful in environmental settings. 相似文献
7.
This study examined differences in the importance of work outcomes between full-time and part-time hospital employees in a sample drawn from five western hospitals (N = 1,876). Work status was operationalized by classifying respondents into four categories based on hours worked per week. Exploratory factor analysis showed that work outcomes may be classified as extrinsic (pay and fringe benefits) and instrinsic (being informed about the job, participating in decision-making, and doing the job well). Confirmatory factor analyses demonstrated that this two-factor structure fits the data well for all four work status categories although the factor loadings differed across categories. Multivariate analyses of variance and covariance indicated that statistically significant differences in the importance of extrinsic and intrinsic outcomes exist for full-time and part-time employees and that these differences persist when various social and demographic variables are held constant. Employees who work fewer hours per week tend to assign less importance to the work outcomes measured in this study. The results suggest that theoretical models of variables such as job satisfaction should take into account work status differences in the importance of work-related outcomes. In addition, managers may find that workers respond to different reward structures depending on the degree of their involvement in the organization. 相似文献
8.
Ruth?SalwayEmail author Jonathan?Wakefield 《Environmental and Ecological Statistics》2005,12(3):321-347
Ecological studies investigate relationships at the level of the group, rather than at the level of the individual. Although
such studies are a common design in epidemiology, it is well-known that estimates may be subject to ecological bias. Most
discussion of ecological bias has focused on rare disease events, where the tractability of the loglinear model allows some
characterization of the nature of different biases. This paper concentrates on non-rare events, where the Poisson approximation
to the binomial distribution is not appropriate. We limit the discussion to bias that arises from within-area variability
in exposures and confounders. Our aims are to investigate the likely sizes and directions of bias and, where possible, to
suggest methods for controlling the bias or for addressing the sensitivity of inference to assumptions on the nature of the
bias. We illustrate that for non-rare events it is much more difficult to characterize the direction of bias than in the rare
case. A series of simple numerical examples based on a chronic study of respiratory health illustrate the ideas of the paper. 相似文献
9.
Elizabeth K. Mackley Richard A. Phillips Janet R. D. Silk Ewan D. Wakefield Vsevolod Afanasyev Robert W. Furness 《Marine Biology》2011,158(2):429-438
Despite the recent burgeoning in predator tracking studies, few report on seabird activity patterns, despite the potential
to provide important insights into foraging ecology and distribution. In the first year-round study for any small petrel,
we examined the activity patterns of the white-chinned petrel Procellaria aequinoctialis based on data from combination geolocator-immersion loggers deployed on adults at South Georgia. The petrels were highly
nocturnal, flying for greater proportions of darkness than any large procellarid studied so far, except the light-mantled
albatross Phoebetria palpebrata. Flight bout durations were short compared with other species, suggesting a dominant foraging mode of small-scale searching
within large prey patches. When migrating, birds reduced the proportion of time on the water and increased flight bout duration.
Activity patterns changed seasonally: birds flew least during the nonbreeding period, and most frequently during chick-rearing
in order to meet higher energy demands associated with provisioning offspring. The degree of their response to moonlight was
also stage dependent (greatest in nonbreeding, and weakest in incubating birds), a trait potentially shared by other nocturnal
petrels which will have repercussions for feeding success and prey selection. For the white-chinned petrel, which is commonly
caught in longline fisheries, these results can be used to identify periods when birds are most susceptible to bycatch, and
therefore when use of mitigation and checking for compliance is critical. 相似文献
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