Reef size and isolation determine the temporal stability of coral reef fish populations

Temporal variance in species abundance, a potential driver of extinction, is linked to mean abundance through Taylor's power law, the empirical observation of a linear log-log relationship with a slope between 1 and 2 for most species. Here we test the idea that the slope of Taylor's power law can vary both among species and spatially as a function of habitat area and isolation. We used the world's most extensive database of coral reef fish communities comprising a 15-year series of fish abundances on 43 reefs of Australia's Great Barrier Reef. Greater temporal variances were observed at small and isolated reefs, and lower variances at large and connected ones. The combination of reef area and isolation was associated with an even greater effect on temporal variances, indicating strong empirical support for the idea that populations on small and isolated reefs will succumb more frequently to local extinction via higher temporal variability, resulting in lower resilience at the community level. Based on these relationships, we constructed a regional predictive map of the dynamic fragility of coral reef fish assemblages on the Great Barrier Reef.     

Selenium content of rice,mixed plant foods and fish from Bangladesh

Static and dynamic adsorption studies of Co (II) ions have been undertaken at fixed pH and ionic strength taking binary biopolymeric beads of cross-linked calcium alginate and carboxy methylcellulose as biosorbents. The adsorption data were applied to Langmuir and Freundlich isotherm equations and various static parameters were calculated. The dynamic nature of adsorption process was quantified in terms of several kinetic constants such as rate constants for adsorption (K) and Lagergreen rate constant (K _ad). The influence of various experimental parameters such as solid-to-liquid ratio, pH, and temperature, the presence of salts and chemical composition of biopolymeric beads were investigated on the adsorption of cobalt ions.     

Maternal employment experiences,attention problems and behavioral performance: A mediational model

The present study posits and empirically tests a process model examining the effects of interrole conflict, satisfaction with, and commitment to the role of employed mother on a self-report measure of cognitive difficulties and a behavioral measure relevant to work performance (proof reading). Fifty-three full-time employed mothers with at least one child living at home participated. The proposed model, tested using Lisrel VI, provided an excellent fit to the data. Specifically, interrole conflict exerted an indirect effect on proof reading performance, mediated by self-reported attention and concentration difficulties. Satisfaction with and commitment to the role of employed mother were not related to either proof reading performance or self-reported cognitive difficulties.     

Interrole conflict,family support and marital adjustment of employed mothers: A short term,longitudinal study

Previous research has found that employed mothers experience conflict between the roles of mother and employee, and that interrole conflict is negatively correlated with marital adjustment. Furthermore, research has shown that social support and personality hardiness moderate the interrole conflict/marital adjustment relationship. However, a longitudinal assessment of the effect of interrole conflict on marital adjustment has not been conducted, nor has the moderating role of social support and hardiness been considered within the same analysis. To address these two issues, the interrole conflict, family support, personality hardiness and marital adjustment of 51 employed mothers were assessed twice, three months apart. Using hierarchical regression analyses, interrole conflict and family support exerted main effects on marital adjustment at time 1, More importantly, a significant interrole conflict/family support interaction predicted change in marital adjustment over three months. High family support exerted a negative impact on marital adjustment when interrole conflict was high. The alternative hypothesis that initial levels of marital adjustment predict change in interrole conflict was tested but not supported.     

Some psychological consequences of striking: A six month,longitudinal study

The literature available on organizational psychology has largely neglected the issue of industrial conflict, and little is known about individual psychological effects of industrial conflict such as labour disputes and strikes. Psychological consequences of involvement in a strike were assessed in this research. Data were collected from 117 full-time, white collar union members immediately following a 22 day strike, and again two and six months later. Negatively perceived industrial relations events (e.g. 'strike or lockout', 'being involved in negotiations') were associated with marital adjustment, psychosomatic symptoms and a lack of psychological well-being on completion of the strike, and predicted unfavourable changes in psychological well-being over the next two and six months. A framework for understanding the negative effects of labour disputes and strikes is proposed, and the role of the organizational psychologist when such conflicts occur is considered.     

Levels of "toxic" and "essential" metals in samples of bovine milk from various dairy farms in Calabria, Italy

The aim of this research was to evaluate the possible contamination by heavy metals of milk from cows bred on various farms in Calabria. The concentrations of heavy metals were determined in 40 samples of bovine milk from the various dairy farms. Each sample, homogenized and powdered, was mineralized in a microwave oven. Quantitative analyses of Cd, Cr, Cu, Pb and Se were performed using an atomic absorption spectrophotometer with graphite furnace; As was analyzed by hot vapor generation technique and Zn with the flame method. As regards toxic heavy metals, highest values are those of As (g.m. 37.90 microg/kg w.w.) and Pb (g.m. 1.32 microg/kg w.w.), while lowest concentrations are those of Cd (g.m. 0.02 microg/kg w.w). With regard to essential metals, Zn (g.m. 2016 microg/kg w.w) and Se (g.m. 13.24 microg/kg w.w.) showed the highest concentrations, followed by Cr (g.m. 2.03 microg/kg w.w.) and Cu (g.m. 1.98 microg/kg w.w.). Further investigations of the levels of heavy metals (As) in a greater number of milk samples from various zones of Calabria are necessary, both to examine this problem from the clinical epidemiological point of view and to identify the possible causes of milk contamination.     

Are “job hoppers” trapped in hedonic treadmills? Effects of career orientations on newcomers' attitude trajectories

Joining a new organization to change jobs is an influential event in an employee's career. Thus, inter-organizational job changes have sparked growing scholarly interest, especially in the temporal dynamics involved in detaching from organizations and adapting to new ones. While it is widely accepted that employees adapt differently to job changes, the influence of employees' career orientations on changes in job attitudes has not yet been considered. This is surprising given that a key difference between self-centered and organization-centered career orientations is a positive attitude toward job changes. Building on hedonic adaptation, we examined how career orientations influence changes in job satisfaction and turnover intention throughout a job change. We compared self-centered and organization-centered employees using random coefficient modeling on two longitudinal data sets with voluntary job changers. Our results illustrate that self-centered career orientations foster a stronger decline in job satisfaction with the new employer, as well as a larger increase in turnover intention, than organization-centered career orientations. In contrast, employees with organization-centered career orientations experienced an upward trend in job satisfaction toward the end of the first year. Our findings offer important implications for research on the determinants of job attitude trajectories when individuals join a new organization.     

Teenagers' part-time employment and their work-related attitudes and aspirations

We assessed the relationship between the quality (i.e., job characteristics, role stressors, and interpersonal relationships) and quantity of part-time employment, and work-related attitudes and aspirations among 349 students. Neither the linear nor the quadratic components of employment quantity predicted any of the outcome variables. Motivation to do good work was predicted both by role stressors and by family achievement orientation. Career maturity was predicted by role stressors at work, and cynicism by role stressors and satisfaction with interpersonal relationships. In contrast, job involvement was significantly related to family achievement orientation but not to any perceived job factors. These findings question the assumption that only intensive work during high school exerts negative effects for teenagers, and support the importance of employment quality for teenagers as well as adults. © 1998 John Wiley & Sons, Ltd.     

Trait synergisms and the rarity, extirpation, and extinction risk of desert fishes

Understanding the causes and consequences of species extinctions is a central goal in ecology. Faced with the difficult task of identifying those species with the greatest need for conservation, ecologists have turned to using predictive suites of ecological and life-history traits to provide reasonable estimates of species extinction risk. Previous studies have linked individual traits to extinction risk, yet the nonadditive contribution of multiple traits to the entire extinction process, from species rarity to local extirpation to global extinction, has not been examined. This study asks whether trait synergisms predispose native fishes of the Lower Colorado River Basin (USA) to risk of extinction through their effects on rarity and local extirpation and their vulnerability to different sources of threat. Fish species with "slow" life histories (e.g., large body size, long life, and delayed maturity), minimal parental care to offspring, and specialized feeding behaviors are associated with smaller geographic distribution, greater frequency of local extirpation, and higher perceived extinction risk than that expected by simple additive effects of traits in combination. This supports the notion that trait synergisms increase the susceptibility of native fishes to multiple stages of the extinction process, thus making them prone to the multiple jeopardies resulting from a combination of fewer individuals, narrow environmental tolerances, and long recovery times following environmental change. Given that particular traits, some acting in concert, may differentially predispose native fishes to rarity, extirpation, and extinction, we suggest that management efforts in the Lower Colorado River Basin should be congruent with the life-history requirements of multiple species over large spatial and temporal scales.     

Cross-correlation bias in lag analysis of aquatic time series

Cross-correlation analysis is the most valuable and widely used statistical tool for evaluating the strength and direction of time-lagged relationships between ecological variables. Although it is well understood that temporal autocorrelation can inflate estimates of cross correlations and cause high rates of incorrectly concluding that lags exist among time series (i.e. type I error), in this study we show that a problem we term intra-multiplicity can cause substantial bias in cross-correlation analysis even in the absence of autocorrelation. Intra-multiplicity refers to the numerous time lags examined and cross-correlation coefficients computed within a pair of time series during cross-correlation analysis. We show using Monte Carlo simulations that intra-multiplicity can spuriously inflate estimates of cross correlations by identifying incorrect time lags. Further, unlike autocorrelation, which generally identifies lags close to the true lag, intra-multiplicity can erroneously identify lags anywhere in the time series and commonly results in a direction change of the correlation (i.e. positive or negative). Using Monte Carlo simulations we develop formulas that quantify the bias introduced by intra-multiplicity as a function of sample size, true cross correlation between the series, and the number of time lags examined. A priori these formulas enable researchers to determine the sample size needed to minimize the biases introduced by intra-multiplicity. A posteriori the formulas can be used to predict the expected bias and type I error rate associated with the data at hand, as well as the maximum number of time lags that can be analyzed to minimize the effects of intra-multiplicity. We examine the relationship between commercial catch of chum salmon and surface temperatures of the North Pacific (1925–1992) to illustrate the problems of intra-multiplicity in fisheries studies and the application of our formulas. These analyses provide a more robust framework to assess the temporal relationships between ecological variables. Received: 28 July 2000 / Accepted: 6 December 2000