Use of stochastic patch occupancy models in the California red-legged frog for Bayesian inference regarding past events and future persistence

Assessing causes of population decline is critically important to management of threatened species. Stochastic patch occupancy models (SPOMs) are popular tools for examining spatial and temporal dynamics of populations when presence–absence data in multiple habitat patches are available. We developed a Bayesian Markov chain method that extends existing SPOMs by focusing on past environmental changes that may have altered occupancy patterns prior to the beginning of data collection. Using occupancy data from 3 creeks, we applied the method to assess 2 hypothesized causes of population decline—in situ die-off and residual impact of past source population loss—in the California red-legged frog. Despite having no data for the 20–30 years between the hypothetical event leading to population decline and the first data collected, we were able to discriminate among hypotheses, finding evidence that in situ die-off increased in 2 of the creeks. Although the creeks had comparable numbers of occupied segments, owing to different extinction–colonization dynamics, our model predicted an 8-fold difference in persistence probabilities of their populations to 2030. Adding a source population led to a greater predicted persistence probability than did decreasing the in situ die-off, emphasizing that reversing the deleterious impacts of a disturbance may not be the most efficient management strategy. We expect our method will be useful for studying dynamics and evaluating management strategies of many species.     

Terrestrial, benthic, and pelagic resource use in lakes: results from a three-isotope Bayesian mixing model

Fluxes of organic matter across habitat boundaries are common in food webs. These fluxes may strongly influence community dynamics, depending on the extent to which they are used by consumers. Yet understanding of basal resource use by consumers is limited, because describing trophic pathways in complex food webs is difficult. We quantified resource use for zooplankton, zoobenthos, and fishes in four low-productivity lakes, using a Bayesian mixing model and measurements of hydrogen, carbon, and nitrogen stable isotope ratios. Multiple sources of uncertainty were explicitly incorporated into the model. As a result, posterior estimates of resource use were often broad distributions; nevertheless, clear patterns were evident. Zooplankton relied on terrestrial and pelagic primary production, while zoobenthos and fishes relied on terrestrial and benthic primary production. Across all consumer groups terrestrial reliance tended to be higher, and benthic reliance lower, in lakes where light penetration was low due to inputs of terrestrial dissolved organic carbon. These results support and refine an emerging consensus that terrestrial and benthic support of lake food webs can be substantial, and they imply that changes in the relative availability of basal resources drive the strength of cross-habitat trophic connections.     

A misdiagnosis of X-linked adrenoleucodystrophy in cultured chorionic villus cells by the measurement of very long chain fatty acids

A case is reported of a male fetus at risk of X-linked adrenoleucodystrophy who showed a normal cultured chorionic villus cell very long chain fatty acid (VLCFA) profile but at birth exhibited grossly abnormal plasma and cultured fibroblast VLCFAs. Maternal contamination or a sample mix-up was excluded by chromosome analysis and analysis of polymorphic markers. This is the second report of a fetus affected with this disorder who showed normal cultured chorionic villus cell VLCFAs. It highlights the importance of a proper audit of all prenatal diagnoses to evaluate method reliability.     

Laboratory Investigation of a New Trommel Model

Abstract

Rotary screens, or trommels, are an important unit operation in material and fuel processing. A computer model has been developed based upon fundamental mechanics. The coefficients and variables employed in the model thus have real physical meaning; adjusting them based upon laboratory data allows the model user to draw conclusions about the behavior of the trommel that can be applied to design and operational changes. The laboratory testing program was specifically designed to test the model described in this paper.

The model proved able to track the laboratory data. Important phenomena that were validated or revealed included the significance of particle layering, changes in bed sliding with rotational velocity, and the pre-eminence of residence time.     

Internet-Based Delphi Research: Case Based Discussion

The interactive capacity of the Internet offers benefits that are intimately linked with contemporary research innovation in the natural resource and environmental studies domains. However, e-research methodologies, such as the e-Delphi technique, have yet to undergo critical review. This study advances methodological discourse on the e-Delphi technique by critically assessing an e-Delphi case study. The analysis suggests that the benefits of using e-Delphi are noteworthy but the authors acknowledge that researchers are likely to face challenges that could potentially compromise research validity and reliability. To ensure that these issues are sufficiently considered when planning and designing an e-Delphi, important facets of the technique are discussed and recommendations are offered to help the environmental researcher avoid potential pitfalls associated with coordinating e-Delphi research.     

Ciliary Activity and Pulmonary Retention of Inhaled Dust In Rats Exposed to Sulfur Dioxide

While the ciliary activity in the airways of rats exposed to sulfur dioxide at low concentration has been studied repeatedly, the effects of chronic exposure to realistic levels of sulfur dioxide and particulates has not been determined. This paper describes the response of white albino rats to the inhalation of low concentrations of sulfur dioxide while exposed to relatively high concentrations of an inert dust. Test results indicate that no change is found in the ciliary activity or the relative number of dust cells in the alveolar structure of rats exposed to 1 ppm of sulfur dioxide and 1 mg/m³ of a graphite dust.     

Emotion as mediators of the relations between perceived supervisor support and psychological hardiness on employee cynicism

In this study we explore whether emotion experienced at work mediates the relationships between perceived supervisor support, psychological hardiness, and employee cynicism. Data were collected from employees working at a medical technology company located in Switzerland. Mediational analyses showed that employees' positive and negative emotions experienced amidst an organizational crisis fully accounted for the relations between perceived supervisor support and cynicism and psychological hardiness and cynicism. Practical implications and directions for future research are discussed. Copyright © 2006 John Wiley & Sons, Ltd.     

Statistical Analysis of Spatial Pattern: A Comparison of Grid and Hierarchical Sampling Approaches

Previous studies have combined random-site hierarchical sampling designs with analysis of variance techniques, and grid sampling with spatial autocorrelation analysis. We illustrate that analysis techniques and sampling designs are interchangeable using densities of an infaunal bivalve from a study in Poverty Bay, New Zealand. Hierarchical designs allow the estimation of variances associated with each level, but high-level factors are imprecisely estimated, and they are inefficient for describing spatial pattern. Grid designs are efficient for describing spatial pattern, and are amenable to conventional analysis. Our example deals with a continuous spatial habitat, but our conclusions also apply in disjunct or patchy habitats. The influence of errors in positioning is also assessed. The advantages of systematic sampling are reviewed, and more efficient hierarchical approaches are identified. The distinction between biological and statisticalsignificance in all analyses is emphasised.     

Does breathing apparatus affect fish counts and observations? A comparison at three New Zealand fished and protected areas

Across three areas, open-circuit scuba (OC) and rebreather (RB) surveys produced similar results for the density and size distribution of fish species inside and outside marine reserves. At Tonga Island, more Notolabrus celidotus were counted with OC than with RB, independently of reserve status [log-scale response ratio of OC/RB (RR) = 0.7]. At Long Island, differences in abundance of Parapercis colias between sampling methods were small at reserve sites (RR = −0.1), but more were counted with scuba than with RBs at fished sites (RR = 0.5). RRs for Pagrus auratus were −1.0 in fished areas and 0.3 in the reserve at Leigh. We also sampled each site using a baited video system (BUV) to establish whether diver-transects sampled the full size range of target species. Most fish in BUV views were Parapercis colias at Long Island (97%), and Pagrus auratus at Leigh (77%). Size structures of Parapercis colias were similar among all three sampling methods within reserve and fished areas at Long Island (max. chi-squared distance = 0.11). BUV samples for Pagrus auratus at Leigh did not detect a prominent juvenile size class observed by divers, but size-frequency distributions of OC, RB, and BUV corresponded at sizes beyond 15 cm TL (max. chi-squared distance = 0.08). To investigate the effects of diver sound on fish behaviour at Long Island, we also compared fish activity when divers with RBs or scuba were present, when the sound of each breathing apparatus was replayed underwater, when no divers were present and no sound was replayed, and when bait was provided, within the reserve only. The lowest number of fish visits to the focal area (mean of 3.0 per 10 min) for Parapercis colias occurred with RB divers present. Maximum abundances of Parapercis colias in all speaker treatments averaged 4.1 per 10 min, whereas with scuba divers present maximum abundances were 5.7, and with baits the average was 38.0 per 10 min.